diff --git a/httprunner/api.py b/httprunner/api.py
index 45ab9318..3018028d 100644
--- a/httprunner/api.py
+++ b/httprunner/api.py
@@ -48,6 +48,8 @@ class HttpRunner(object):
                 }
 
         """
+        loader.reset_loader()
+
         # load .env
         loader.load_dot_env_file(dot_env_path)
 
@@ -98,6 +100,21 @@ class HttpRunner(object):
 
         """
         if validator.is_testcases(path_or_testcases):
+            # TODO: refactor
+            if isinstance(path_or_testcases, list):
+                for testcase in path_or_testcases:
+                    try:
+                        dir_path = os.path.dirname(testcase["config"]["path"])
+                        loader.load_debugtalk_module(dir_path)
+                    except KeyError:
+                        pass
+            else:
+                try:
+                    dir_path = os.path.dirname(path_or_testcases["config"]["path"])
+                    loader.load_debugtalk_module(dir_path)
+                except KeyError:
+                    pass
+
             testcases = path_or_testcases
         else:
             testcases = loader.load_testcases(path_or_testcases)
@@ -170,6 +187,9 @@ class HttpRunner(object):
                     config_variables,
                     self.project_mapping["debugtalk"]["functions"]
                 )
+
+                # put loaded project functions to config
+                testcase["config"]["functions"] = self.project_mapping["debugtalk"]["functions"]
                 parsed_testcases_list.append(testcase)
 
         return parsed_testcases_list
@@ -300,6 +320,7 @@ class LocustRunner(object):
         try:
             self.runner.run(path)
         except exceptions.MyBaseError as ex:
+            # TODO: refactor
             from locust.events import request_failure
             request_failure.fire(
                 request_type=test.testcase_dict.get("request", {}).get("method"),
diff --git a/httprunner/context.py b/httprunner/context.py
index fba6ef8b..ba3d80b7 100644
--- a/httprunner/context.py
+++ b/httprunner/context.py
@@ -1,447 +1,211 @@
 # encoding: utf-8
 
 import copy
-import os
-import random
-import re
-import sys
 
-from httprunner import built_in, exceptions, loader, logger, parser, utils
-from httprunner.compat import OrderedDict, basestring, builtin_str, str
+from httprunner import exceptions, logger, parser, utils
+from httprunner.compat import OrderedDict
 
+# def parse_parameters(parameters, testset_path=None):
+#     """ parse parameters and generate cartesian product.
 
-def parse_parameters(parameters, testset_path=None):
-    """ parse parameters and generate cartesian product.
+#     Args:
+#         parameters (list) parameters: parameter name and value in list
+#             parameter value may be in three types:
+#                 (1) data list, e.g. ["iOS/10.1", "iOS/10.2", "iOS/10.3"]
+#                 (2) call built-in parameterize function, "${parameterize(account.csv)}"
+#                 (3) call custom function in debugtalk.py, "${gen_app_version()}"
 
-    Args:
-        parameters (list) parameters: parameter name and value in list
-            parameter value may be in three types:
-                (1) data list, e.g. ["iOS/10.1", "iOS/10.2", "iOS/10.3"]
-                (2) call built-in parameterize function, "${parameterize(account.csv)}"
-                (3) call custom function in debugtalk.py, "${gen_app_version()}"
+#         testset_path (str): testset file path, used for locating csv file and debugtalk.py
 
-        testset_path (str): testset file path, used for locating csv file and debugtalk.py
+#     Returns:
+#         list: cartesian product list
 
-    Returns:
-        list: cartesian product list
+#     Examples:
+#         >>> parameters = [
+#             {"user_agent": ["iOS/10.1", "iOS/10.2", "iOS/10.3"]},
+#             {"username-password": "${parameterize(account.csv)}"},
+#             {"app_version": "${gen_app_version()}"}
+#         ]
+#         >>> parse_parameters(parameters)
 
-    Examples:
-        >>> parameters = [
-            {"user_agent": ["iOS/10.1", "iOS/10.2", "iOS/10.3"]},
-            {"username-password": "${parameterize(account.csv)}"},
-            {"app_version": "${gen_app_version()}"}
-        ]
-        >>> parse_parameters(parameters)
+#     """
+#     testcase_parser = TestcaseParser(file_path=testset_path)
 
-    """
-    testcase_parser = TestcaseParser(file_path=testset_path)
+#     parsed_parameters_list = []
+#     for parameter in parameters:
+#         parameter_name, parameter_content = list(parameter.items())[0]
+#         parameter_name_list = parameter_name.split("-")
 
-    parsed_parameters_list = []
-    for parameter in parameters:
-        parameter_name, parameter_content = list(parameter.items())[0]
-        parameter_name_list = parameter_name.split("-")
+#         if isinstance(parameter_content, list):
+#             # (1) data list
+#             # e.g. {"app_version": ["2.8.5", "2.8.6"]}
+#             #       => [{"app_version": "2.8.5", "app_version": "2.8.6"}]
+#             # e.g. {"username-password": [["user1", "111111"], ["test2", "222222"]}
+#             #       => [{"username": "user1", "password": "111111"}, {"username": "user2", "password": "222222"}]
+#             parameter_content_list = []
+#             for parameter_item in parameter_content:
+#                 if not isinstance(parameter_item, (list, tuple)):
+#                     # "2.8.5" => ["2.8.5"]
+#                     parameter_item = [parameter_item]
 
-        if isinstance(parameter_content, list):
-            # (1) data list
-            # e.g. {"app_version": ["2.8.5", "2.8.6"]}
-            #       => [{"app_version": "2.8.5", "app_version": "2.8.6"}]
-            # e.g. {"username-password": [["user1", "111111"], ["test2", "222222"]}
-            #       => [{"username": "user1", "password": "111111"}, {"username": "user2", "password": "222222"}]
-            parameter_content_list = []
-            for parameter_item in parameter_content:
-                if not isinstance(parameter_item, (list, tuple)):
-                    # "2.8.5" => ["2.8.5"]
-                    parameter_item = [parameter_item]
+#                 # ["app_version"], ["2.8.5"] => {"app_version": "2.8.5"}
+#                 # ["username", "password"], ["user1", "111111"] => {"username": "user1", "password": "111111"}
+#                 parameter_content_dict = dict(zip(parameter_name_list, parameter_item))
 
-                # ["app_version"], ["2.8.5"] => {"app_version": "2.8.5"}
-                # ["username", "password"], ["user1", "111111"] => {"username": "user1", "password": "111111"}
-                parameter_content_dict = dict(zip(parameter_name_list, parameter_item))
+#                 parameter_content_list.append(parameter_content_dict)
+#         else:
+#             # (2) & (3)
+#             parsed_parameter_content = testcase_parser.eval_content_with_bindings(parameter_content)
+#             # e.g. [{'app_version': '2.8.5'}, {'app_version': '2.8.6'}]
+#             # e.g. [{"username": "user1", "password": "111111"}, {"username": "user2", "password": "222222"}]
+#             if not isinstance(parsed_parameter_content, list):
+#                 raise exceptions.ParamsError("parameters syntax error!")
 
-                parameter_content_list.append(parameter_content_dict)
-        else:
-            # (2) & (3)
-            parsed_parameter_content = testcase_parser.eval_content_with_bindings(parameter_content)
-            # e.g. [{'app_version': '2.8.5'}, {'app_version': '2.8.6'}]
-            # e.g. [{"username": "user1", "password": "111111"}, {"username": "user2", "password": "222222"}]
-            if not isinstance(parsed_parameter_content, list):
-                raise exceptions.ParamsError("parameters syntax error!")
+#             parameter_content_list = [
+#                 # get subset by parameter name
+#                 {key: parameter_item[key] for key in parameter_name_list}
+#                 for parameter_item in parsed_parameter_content
+#             ]
 
-            parameter_content_list = [
-                # get subset by parameter name
-                {key: parameter_item[key] for key in parameter_name_list}
-                for parameter_item in parsed_parameter_content
-            ]
+#         parsed_parameters_list.append(parameter_content_list)
 
-        parsed_parameters_list.append(parameter_content_list)
-
-    return utils.gen_cartesian_product(*parsed_parameters_list)
-
-
-class TestcaseParser(object):
-
-    def __init__(self, variables={}, functions={}, file_path=None):
-        self.update_binded_variables(variables)
-        self.bind_functions(functions)
-        self.file_path = file_path
-
-    def update_binded_variables(self, variables):
-        """ bind variables to current testcase parser
-        @param (dict) variables, variables binds mapping
-            {
-                "authorization": "a83de0ff8d2e896dbd8efb81ba14e17d",
-                "random": "A2dEx",
-                "data": {"name": "user", "password": "123456"},
-                "uuid": 1000
-            }
-        """
-        self.variables = variables
-
-    def bind_functions(self, functions):
-        """ bind functions to current testcase parser
-        @param (dict) functions, functions binds mapping
-            {
-                "add_two_nums": lambda a, b=1: a + b
-            }
-        """
-        self.functions = functions
-
-    def _get_bind_item(self, item_type, item_name):
-        """ get specified function or variable.
-
-        Args:
-            item_type(str): functions or variables
-            item_name(str): function name or variable name
-
-        Returns:
-            object: specified function or variable object.
-        """
-        if item_type == "functions":
-            if item_name in self.functions:
-                return self.functions[item_name]
-
-            try:
-                # check if builtin functions
-                item_func = eval(item_name)
-                if callable(item_func):
-                    # is builtin function
-                    return item_func
-            except (NameError, TypeError):
-                # is not builtin function, continue to search
-                pass
-        else:
-            # item_type == "variables":
-            if item_name in self.variables:
-                return self.variables[item_name]
-
-        debugtalk_module = loader.load_debugtalk_module(self.file_path)
-        return loader.get_module_item(debugtalk_module, item_type, item_name)
-
-    def get_bind_function(self, func_name):
-        return self._get_bind_item("functions", func_name)
-
-    def get_bind_variable(self, variable_name):
-        return self._get_bind_item("variables", variable_name)
-
-    def load_csv_list(self, csv_file_name, fetch_method="Sequential"):
-        """ locate csv file and load csv content.
-
-        Args:
-            csv_file_name (str): csv file name
-            fetch_method (str): fetch data method, defaults to Sequential.
-                If set to "random", csv data list will be reordered in random.
-
-        Returns:
-            list: csv data list
-        """
-        csv_file_path = loader.locate_file(self.file_path, csv_file_name)
-        csv_content_list = loader.load_file(csv_file_path)
-
-        if fetch_method.lower() == "random":
-            random.shuffle(csv_content_list)
-
-        return csv_content_list
-
-    def _eval_content_functions(self, content):
-        functions_list = parser.extract_functions(content)
-        for func_content in functions_list:
-            function_meta = parser.parse_function(func_content)
-            func_name = function_meta['func_name']
-
-            args = function_meta.get('args', [])
-            kwargs = function_meta.get('kwargs', {})
-            args = self.eval_content_with_bindings(args)
-            kwargs = self.eval_content_with_bindings(kwargs)
-
-            if func_name in ["parameterize", "P"]:
-                eval_value = self.load_csv_list(*args, **kwargs)
-            else:
-                func = self.get_bind_function(func_name)
-                eval_value = func(*args, **kwargs)
-
-            func_content = "${" + func_content + "}"
-            if func_content == content:
-                # content is a variable
-                content = eval_value
-            else:
-                # content contains one or many variables
-                content = content.replace(
-                    func_content,
-                    str(eval_value), 1
-                )
-
-        return content
-
-    def _eval_content_variables(self, content):
-        """ replace all variables of string content with mapping value.
-        @param (str) content
-        @return (str) parsed content
-
-        e.g.
-            variable_mapping = {
-                "var_1": "abc",
-                "var_2": "def"
-            }
-            $var_1 => "abc"
-            $var_1#XYZ => "abc#XYZ"
-            /$var_1/$var_2/var3 => "/abc/def/var3"
-            ${func($var_1, $var_2, xyz)} => "${func(abc, def, xyz)}"
-        """
-        variables_list = parser.extract_variables(content)
-        for variable_name in variables_list:
-            variable_value = self.get_bind_variable(variable_name)
-
-            if "${}".format(variable_name) == content:
-                # content is a variable
-                content = variable_value
-            else:
-                # content contains one or several variables
-                if not isinstance(variable_value, str):
-                    variable_value = builtin_str(variable_value)
-
-                content = content.replace(
-                    "${}".format(variable_name),
-                    variable_value, 1
-                )
-
-        return content
-
-    def eval_content_with_bindings(self, content):
-        """ parse content recursively, each variable and function in content will be evaluated.
-
-        @param (dict) content in any data structure
-            {
-                "url": "http://127.0.0.1:5000/api/users/$uid/${add_two_nums(1, 1)}",
-                "method": "POST",
-                "headers": {
-                    "Content-Type": "application/json",
-                    "authorization": "$authorization",
-                    "random": "$random",
-                    "sum": "${add_two_nums(1, 2)}"
-                },
-                "body": "$data"
-            }
-        @return (dict) parsed content with evaluated bind values
-            {
-                "url": "http://127.0.0.1:5000/api/users/1000/2",
-                "method": "POST",
-                "headers": {
-                    "Content-Type": "application/json",
-                    "authorization": "a83de0ff8d2e896dbd8efb81ba14e17d",
-                    "random": "A2dEx",
-                    "sum": 3
-                },
-                "body": {"name": "user", "password": "123456"}
-            }
-        """
-        if content is None:
-            return None
-
-        if isinstance(content, (list, tuple)):
-            return [
-                self.eval_content_with_bindings(item)
-                for item in content
-            ]
-
-        if isinstance(content, dict):
-            evaluated_data = {}
-            for key, value in content.items():
-                eval_key = self.eval_content_with_bindings(key)
-                eval_value = self.eval_content_with_bindings(value)
-                evaluated_data[eval_key] = eval_value
-
-            return evaluated_data
-
-        if isinstance(content, basestring):
-
-            # content is in string format here
-            content = content.strip()
-
-            # replace functions with evaluated value
-            # Notice: _eval_content_functions must be called before _eval_content_variables
-            content = self._eval_content_functions(content)
-
-            # replace variables with binding value
-            content = self._eval_content_variables(content)
-
-        return content
+#     return utils.gen_cartesian_product(*parsed_parameters_list)
 
 
 class Context(object):
     """ Manages context functions and variables.
-        context has two levels, testset and testcase.
+        context has two levels, testcase and teststep.
     """
-    def __init__(self):
-        self.testset_shared_variables_mapping = OrderedDict()
-        self.testcase_variables_mapping = OrderedDict()
-        self.testcase_parser = TestcaseParser()
+    def __init__(self, variables=None, functions=None):
+        """ init Context with testcase variables and functions.
+        """
+        # testcase level context
+        ## TESTCASE_SHARED_VARIABLES_MAPPING and TESTCASE_SHARED_FUNCTIONS_MAPPING will not change.
+        self.TESTCASE_SHARED_VARIABLES_MAPPING = variables or OrderedDict()
+        self.TESTCASE_SHARED_FUNCTIONS_MAPPING = functions or OrderedDict()
+
+        # testcase level request, will not change
+        self.TESTCASE_SHARED_REQUEST_MAPPING = {}
+
         self.evaluated_validators = []
-        self.init_context()
+        self.init_context_variables(level="testcase")
+
+    def init_context_variables(self, level="testcase"):
+        """ initialize testcase/teststep context
+
+        Args:
+            level (enum): "testcase" or "teststep"
 
-    def init_context(self, level='testset'):
         """
-        testset level context initializes when a file is loaded,
-        testcase level context initializes when each testcase starts.
-        """
-        if level == "testset":
-            self.testset_functions_config = {}
-            self.testset_request_config = {}
-            self.testset_shared_variables_mapping = OrderedDict()
+        if level == "testcase":
+            # testcase level runtime context, will be updated with extracted variables in each teststep.
+            self.testcase_runtime_variables_mapping = copy.deepcopy(self.TESTCASE_SHARED_VARIABLES_MAPPING)
 
-        # testcase config shall inherit from testset configs,
-        # but can not change testset configs, that's why we use copy.deepcopy here.
-        self.testcase_functions_config = copy.deepcopy(self.testset_functions_config)
-        self.testcase_variables_mapping = copy.deepcopy(self.testset_shared_variables_mapping)
+        # teststep level context, will be altered in each teststep.
+        # teststep config shall inherit from testcase configs,
+        # but can not change testcase configs, that's why we use copy.deepcopy here.
+        self.teststep_variables_mapping = copy.deepcopy(self.testcase_runtime_variables_mapping)
 
-        self.testcase_parser.bind_functions(self.testcase_functions_config)
-        self.testcase_parser.update_binded_variables(self.testcase_variables_mapping)
+    def update_context_variables(self, variables, level):
+        """ update context variables, with level specified.
 
-        if level == "testset":
-            self.import_module_items(built_in)
+        Args:
+            variables (list/OrderedDict): testcase config block or teststep block
+                [
+                    {"TOKEN": "debugtalk"},
+                    {"random": "${gen_random_string(5)}"},
+                    {"json": {'name': 'user', 'password': '123456'}},
+                    {"md5": "${gen_md5($TOKEN, $json, $random)}"}
+                ]
+                OrderDict({
+                    "TOKEN": "debugtalk",
+                    "random": "${gen_random_string(5)}",
+                    "json": {'name': 'user', 'password': '123456'},
+                    "md5": "${gen_md5($TOKEN, $json, $random)}"
+                })
+            level (enum): "testcase" or "teststep"
 
-    def config_context(self, config_dict, level):
-        if level == "testset":
-            self.testcase_parser.file_path = config_dict.get("path", None)
-
-        variables = config_dict.get('variables') \
-            or config_dict.get('variable_binds', OrderedDict())
-        self.bind_variables(variables, level)
-
-    def bind_functions(self, function_binds, level="testcase"):
-        """ Bind named functions within the context
-            This allows for passing in self-defined functions in testing.
-            e.g. function_binds:
-            {
-                "add_one": lambda x: x + 1,             # lambda function
-                "add_two_nums": "lambda x, y: x + y"    # lambda function in string
-            }
-        """
-        eval_function_binds = {}
-        for func_name, function in function_binds.items():
-            if isinstance(function, str):
-                function = eval(function)
-            eval_function_binds[func_name] = function
-
-        self.__update_context_functions_config(level, eval_function_binds)
-
-    def import_module_items(self, imported_module):
-        """ import module functions and variables and bind to testset context
-        """
-        module_mapping = loader.load_python_module(imported_module)
-        self.__update_context_functions_config("testset", module_mapping["functions"])
-        self.bind_variables(module_mapping["variables"], "testset")
-
-    def bind_variables(self, variables, level="testcase"):
-        """ bind variables to testset context or current testcase context.
-            variables in testset context can be used in all testcases of current test suite.
-
-        @param (list or OrderDict) variables, variable can be value or custom function.
-            if value is function, it will be called and bind result to variable.
-        e.g.
-            OrderDict({
-                "TOKEN": "debugtalk",
-                "random": "${gen_random_string(5)}",
-                "json": {'name': 'user', 'password': '123456'},
-                "md5": "${gen_md5($TOKEN, $json, $random)}"
-            })
         """
         if isinstance(variables, list):
             variables = utils.convert_mappinglist_to_orderdict(variables)
 
-        for variable_name, value in variables.items():
-            variable_eval_value = self.eval_content(value)
+        for variable_name, variable_value in variables.items():
+            variable_eval_value = self.eval_content(variable_value)
 
-            if level == "testset":
-                self.testset_shared_variables_mapping[variable_name] = variable_eval_value
+            if level == "testcase":
+                self.testcase_runtime_variables_mapping[variable_name] = variable_eval_value
 
-            self.bind_testcase_variable(variable_name, variable_eval_value)
-
-    def bind_testcase_variable(self, variable_name, variable_value):
-        """ bind and update testcase variables mapping
-        """
-        self.testcase_variables_mapping[variable_name] = variable_value
-        self.testcase_parser.update_binded_variables(self.testcase_variables_mapping)
-
-    def bind_extracted_variables(self, variables):
-        """ bind extracted variables to testset context
-        @param (OrderDict) variables
-            extracted value do not need to evaluate.
-        """
-        for variable_name, value in variables.items():
-            self.testset_shared_variables_mapping[variable_name] = value
-            self.bind_testcase_variable(variable_name, value)
-
-    def __update_context_functions_config(self, level, config_mapping):
-        """
-        @param level: testset or testcase
-        @param config_type: functions
-        @param config_mapping: functions config mapping
-        """
-        if level == "testset":
-            self.testset_functions_config.update(config_mapping)
-
-        self.testcase_functions_config.update(config_mapping)
-        self.testcase_parser.bind_functions(self.testcase_functions_config)
+            self.update_teststep_variables_mapping(variable_name, variable_eval_value)
 
     def eval_content(self, content):
         """ evaluate content recursively, take effect on each variable and function in content.
             content may be in any data structure, include dict, list, tuple, number, string, etc.
         """
-        return self.testcase_parser.eval_content_with_bindings(content)
+        return parser.parse_data(
+            content,
+            self.teststep_variables_mapping,
+            self.TESTCASE_SHARED_FUNCTIONS_MAPPING
+        )
+
+    def update_testcase_runtime_variables_mapping(self, variables):
+        """ update testcase_runtime_variables_mapping with extracted vairables in teststep.
+
+        Args:
+            variables (OrderDict): extracted variables in teststep
 
-    def get_parsed_request(self, request_dict, level="testcase"):
-        """ get parsed request with bind variables and functions.
-        @param request_dict: request config mapping
-        @param level: testset or testcase
         """
-        if level == "testset":
-            request_dict = self.eval_content(
-                request_dict
+        for variable_name, variable_value in variables.items():
+            self.testcase_runtime_variables_mapping[variable_name] = variable_value
+            self.update_teststep_variables_mapping(variable_name, variable_value)
+
+    def update_teststep_variables_mapping(self, variable_name, variable_value):
+        """ bind and update testcase variables mapping
+        """
+        self.teststep_variables_mapping[variable_name] = variable_value
+
+    def get_parsed_request(self, request_dict, level="teststep"):
+        """ get parsed request with variables and functions.
+
+        Args:
+            request_dict (dict): request config mapping
+            level (enum): "testcase" or "teststep"
+
+        Returns:
+            dict: parsed request dict
+
+        """
+        if level == "testcase":
+            # testcase config request dict has been parsed in __parse_testcases
+            self.TESTCASE_SHARED_REQUEST_MAPPING = request_dict
+            return request_dict
+
+        else:
+            # teststep
+            return self.eval_content(
+                utils.deep_update_dict(
+                    copy.deepcopy(self.TESTCASE_SHARED_REQUEST_MAPPING),
+                    request_dict
+                )
             )
-            self.testset_request_config.update(request_dict)
 
-        testcase_request_config = utils.deep_update_dict(
-            copy.deepcopy(self.testset_request_config),
-            request_dict
-        )
-        parsed_request = self.eval_content(
-            testcase_request_config
-        )
+    def __eval_check_item(self, validator, resp_obj):
+        """ evaluate check item in validator.
 
-        return parsed_request
+        Args:
+            validator (dict): validator
+                {"check": "status_code", "comparator": "eq", "expect": 201}
+                {"check": "$resp_body_success", "comparator": "eq", "expect": True}
+            resp_obj (object): requests.Response() object
+
+        Returns:
+            dict: validator info
+                {
+                    "check": "status_code",
+                    "check_value": 200,
+                    "expect": 201,
+                    "comparator": "eq"
+                }
 
-    def eval_check_item(self, validator, resp_obj):
-        """ evaluate check item in validator
-        @param (dict) validator
-            {"check": "status_code", "comparator": "eq", "expect": 201}
-            {"check": "$resp_body_success", "comparator": "eq", "expect": True}
-        @param (object) resp_obj
-        @return (dict) validator info
-            {
-                "check": "status_code",
-                "check_value": 200,
-                "expect": 201,
-                "comparator": "eq"
-            }
         """
         check_item = validator["check"]
         # check_item should only be the following 5 formats:
@@ -470,12 +234,22 @@ class Context(object):
         validator["check_result"] = "unchecked"
         return validator
 
-    def do_validation(self, validator_dict):
+    def _do_validation(self, validator_dict):
         """ validate with functions
+
+        Args:
+            validator_dict (dict): validator dict
+                {
+                    "check": "status_code",
+                    "check_value": 200,
+                    "expect": 201,
+                    "comparator": "eq"
+                }
+
         """
         # TODO: move comparator uniform to init_test_suites
         comparator = utils.get_uniform_comparator(validator_dict["comparator"])
-        validate_func = self.testcase_parser.get_bind_function(comparator)
+        validate_func = self.TESTCASE_SHARED_FUNCTIONS_MAPPING.get(comparator)
 
         if not validate_func:
             raise exceptions.FunctionNotFound("comparator not found: {}".format(comparator))
@@ -516,26 +290,28 @@ class Context(object):
     def validate(self, validators, resp_obj):
         """ make validations
         """
+        evaluated_validators = []
         if not validators:
-            return
+            return evaluated_validators
 
         logger.log_info("start to validate.")
-        self.evaluated_validators = []
         validate_pass = True
 
         for validator in validators:
             # evaluate validators with context variable mapping.
-            evaluated_validator = self.eval_check_item(
+            evaluated_validator = self.__eval_check_item(
                 parser.parse_validator(validator),
                 resp_obj
             )
 
             try:
-                self.do_validation(evaluated_validator)
+                self._do_validation(evaluated_validator)
             except exceptions.ValidationFailure:
                 validate_pass = False
 
-            self.evaluated_validators.append(evaluated_validator)
+            evaluated_validators.append(evaluated_validator)
 
         if not validate_pass:
             raise exceptions.ValidationFailure
+
+        return evaluated_validators
diff --git a/httprunner/loader.py b/httprunner/loader.py
index 55857907..8a118aea 100644
--- a/httprunner/loader.py
+++ b/httprunner/loader.py
@@ -295,8 +295,15 @@ def load_python_module(module):
     return debugtalk_module
 
 
+def load_builtin_module():
+    """ load built_in module
+    """
+    built_in_module = load_python_module(built_in)
+    project_mapping["debugtalk"] = built_in_module
+
+
 def load_debugtalk_module(start_path=None):
-    """ load built_in module and project debugtalk.py module.
+    """ load project debugtalk.py module and merge with builtin module.
 
     Args:
         start_path (str, optional): start locating path, maybe file path or directory path.
@@ -304,34 +311,27 @@ def load_debugtalk_module(start_path=None):
 
     Returns:
         dict: variables and functions mapping for debugtalk.py
-
             {
                 "variables": {},
                 "functions": {}
             }
 
     """
-    # load built_in module
-    built_in_module = load_python_module(built_in)
-
     start_path = start_path or os.getcwd()
 
     try:
         module_path = locate_file(start_path, "debugtalk.py")
         module_name = convert_module_name(module_path)
     except exceptions.FileNotFound:
-        return built_in_module
+        return
 
     # load debugtalk.py module
     imported_module = importlib.import_module(module_name)
     debugtalk_module = load_python_module(imported_module)
 
     # override built_in module with debugtalk.py module
-    debugtalk_module["variables"].update(built_in_module["variables"])
-    debugtalk_module["functions"].update(built_in_module["functions"])
-
-    project_mapping["debugtalk"] = debugtalk_module
-    return debugtalk_module
+    project_mapping["debugtalk"]["variables"].update(debugtalk_module["variables"])
+    project_mapping["debugtalk"]["functions"].update(debugtalk_module["functions"])
 
 
 def get_module_item(module_mapping, item_type, item_name):
@@ -884,22 +884,27 @@ def load_test_folder(test_folder_path=None):
     return test_definition_mapping
 
 
+def reset_loader():
+    """ reset project mapping.
+    """
+    project_mapping["debugtalk"] = {}
+    project_mapping["env"] = {}
+    project_mapping["def-api"] = {}
+    project_mapping["def-testcase"] = {}
+    testcases_cache_mapping.clear()
+
+
 def load_project_tests(folder_path):
-    """ load api, testcases and debugtalk.py module.
+    """ load api, testcases and builtin module.
 
     Args:
         folder_path (str): folder path.
 
-    Returns:
-        dict: project tests mapping.
-
     """
-    load_debugtalk_module(folder_path)
+    load_builtin_module()
     load_api_folder(os.path.join(folder_path, "api"))
     load_test_folder(os.path.join(folder_path, "suite"))
 
-    return project_mapping
-
 
 def load_testcases(path):
     """ load testcases from file path, extend and merge with api/testcase definitions.
@@ -937,11 +942,14 @@ def load_testcases(path):
         return testcases_cache_mapping[path]
 
     if os.path.isdir(path):
+        load_debugtalk_module(path)
         files_list = load_folder_files(path)
         testcases_list = load_testcases(files_list)
 
     elif os.path.isfile(path):
         try:
+            dir_path = os.path.dirname(path)
+            load_debugtalk_module(dir_path)
             testcase = _load_test_file(path)
             if testcase["teststeps"]:
                 testcases_list = [testcase]
diff --git a/httprunner/parser.py b/httprunner/parser.py
index defc588d..c6115769 100644
--- a/httprunner/parser.py
+++ b/httprunner/parser.py
@@ -492,7 +492,6 @@ def parse_data(content, variables_mapping=None, functions_mapping=None):
 
     """
     # TODO: refactor type check
-    # TODO: combine this with TestcaseParser
     if content is None or isinstance(content, (numeric_types, bool, type)):
         return content
 
diff --git a/httprunner/runner.py b/httprunner/runner.py
index 9ac03981..3eec4659 100644
--- a/httprunner/runner.py
+++ b/httprunner/runner.py
@@ -4,69 +4,83 @@ from unittest.case import SkipTest
 
 from httprunner import exceptions, logger, response, utils
 from httprunner.client import HttpSession
+from httprunner.compat import OrderedDict
 from httprunner.context import Context
 
 
 class Runner(object):
 
     def __init__(self, config_dict=None, http_client_session=None):
+        """
+        """
         self.http_client_session = http_client_session
-        self.context = Context()
-
         config_dict = config_dict or {}
+        self.evaluated_validators = []
 
-        # testset setup hooks
-        testset_setup_hooks = config_dict.pop("setup_hooks", [])
-        # testset teardown hooks
-        self.testset_teardown_hooks = config_dict.pop("teardown_hooks", [])
+        # testcase variables
+        config_variables = config_dict.get("variables", {})
+        # testcase functions
+        config_functions = config_dict.get("functions", {})
+        # testcase setup hooks
+        testcase_setup_hooks = config_dict.pop("setup_hooks", [])
+        # testcase teardown hooks
+        self.testcase_teardown_hooks = config_dict.pop("teardown_hooks", [])
 
-        self.init_config(config_dict, "testset")
+        self.context = Context(config_variables, config_functions)
+        self.init_config(config_dict, "testcase")
 
-        if testset_setup_hooks:
-            self.do_hook_actions(testset_setup_hooks)
+        if testcase_setup_hooks:
+            self.do_hook_actions(testcase_setup_hooks)
 
     def __del__(self):
-        if self.testset_teardown_hooks:
-            self.do_hook_actions(self.testset_teardown_hooks)
+        if self.testcase_teardown_hooks:
+            self.do_hook_actions(self.testcase_teardown_hooks)
 
     def init_config(self, config_dict, level):
         """ create/update context variables binds
-        @param (dict) config_dict
-        @param (str) level, "testset" or "testcase"
-        testset:
-            {
-                "name": "smoke testset",
-                "path": "tests/data/demo_testset_variables.yml",
-                "variables": [],   # optional
-                "request": {
-                    "base_url": "http://127.0.0.1:5000",
-                    "headers": {
-                        "User-Agent": "iOS/2.8.3"
+
+        Args:
+            config_dict (dict):
+            level (enum): "testcase" or "teststep"
+                testcase:
+                    {
+                        "name": "testcase description",
+                        "path": "tests/data/demo_testset_variables.yml",
+                        "variables": [],   # optional
+                        "request": {
+                            "base_url": "http://127.0.0.1:5000",
+                            "headers": {
+                                "User-Agent": "iOS/2.8.3"
+                            }
+                        }
                     }
-                }
-            }
-        testcase:
-            {
-                "name": "testcase description",
-                "variables": [],   # optional
-                "request": {
-                    "url": "/api/get-token",
-                    "method": "POST",
-                    "headers": {
-                        "Content-Type": "application/json"
+                teststep:
+                    {
+                        "name": "teststep description",
+                        "variables": [],   # optional
+                        "request": {
+                            "url": "/api/get-token",
+                            "method": "POST",
+                            "headers": {
+                                "Content-Type": "application/json"
+                            }
+                        },
+                        "json": {
+                            "sign": "f1219719911caae89ccc301679857ebfda115ca2"
+                        }
                     }
-                },
-                "json": {
-                    "sign": "f1219719911caae89ccc301679857ebfda115ca2"
-                }
-            }
-        @param (str) context level, testcase or testset
+
+        Returns:
+            dict: parsed request dict
+
         """
         # convert keys in request headers to lowercase
         config_dict = utils.lower_config_dict_key(config_dict)
 
-        self.context.init_context(level)
-        self.context.config_context(config_dict, level)
+        self.context.init_context_variables(level)
+        variables = config_dict.get('variables') \
+            or config_dict.get('variable_binds', OrderedDict())
+        self.context.update_context_variables(variables, level)
 
         request_config = config_dict.get('request', {})
         parsed_request = self.context.get_parsed_request(request_config, level)
@@ -76,24 +90,32 @@ class Runner(object):
 
         return parsed_request
 
-    def _handle_skip_feature(self, testcase_dict):
-        """ handle skip feature for testcase
+    def _handle_skip_feature(self, teststep_dict):
+        """ handle skip feature for teststep
             - skip: skip current test unconditionally
             - skipIf: skip current test if condition is true
             - skipUnless: skip current test unless condition is true
+
+        Args:
+            teststep_dict (dict): teststep info
+
+        Raises:
+            SkipTest: skip teststep
+
         """
+        # TODO: move skip to __initialize
         skip_reason = None
 
-        if "skip" in testcase_dict:
-            skip_reason = testcase_dict["skip"]
+        if "skip" in teststep_dict:
+            skip_reason = teststep_dict["skip"]
 
-        elif "skipIf" in testcase_dict:
-            skip_if_condition = testcase_dict["skipIf"]
+        elif "skipIf" in teststep_dict:
+            skip_if_condition = teststep_dict["skipIf"]
             if self.context.eval_content(skip_if_condition):
                 skip_reason = "{} evaluate to True".format(skip_if_condition)
 
-        elif "skipUnless" in testcase_dict:
-            skip_unless_condition = testcase_dict["skipUnless"]
+        elif "skipUnless" in teststep_dict:
+            skip_unless_condition = teststep_dict["skipUnless"]
             if not self.context.eval_content(skip_unless_condition):
                 skip_reason = "{} evaluate to False".format(skip_unless_condition)
 
@@ -106,40 +128,49 @@ class Runner(object):
             # TODO: check hook function if valid
             self.context.eval_content(action)
 
-    def run_test(self, testcase_dict):
-        """ run single testcase.
-        @param (dict) testcase_dict
-            {
-                "name": "testcase description",
-                "skip": "skip this test unconditionally",
-                "times": 3,
-                "variables": [],        # optional, override
-                "request": {
-                    "url": "http://127.0.0.1:5000/api/users/1000",
-                    "method": "POST",
-                    "headers": {
-                        "Content-Type": "application/json",
-                        "authorization": "$authorization",
-                        "random": "$random"
+    def run_test(self, teststep_dict):
+        """ run single teststep.
+
+        Args:
+            teststep_dict (dict): teststep info
+                {
+                    "name": "teststep description",
+                    "skip": "skip this test unconditionally",
+                    "times": 3,
+                    "variables": [],        # optional, override
+                    "request": {
+                        "url": "http://127.0.0.1:5000/api/users/1000",
+                        "method": "POST",
+                        "headers": {
+                            "Content-Type": "application/json",
+                            "authorization": "$authorization",
+                            "random": "$random"
+                        },
+                        "body": '{"name": "user", "password": "123456"}'
                     },
-                    "body": '{"name": "user", "password": "123456"}'
-                },
-                "extract": [],              # optional
-                "validate": [],             # optional
-                "setup_hooks": [],          # optional
-                "teardown_hooks": []        # optional
-            }
-        @return True or raise exception during test
+                    "extract": [],              # optional
+                    "validate": [],             # optional
+                    "setup_hooks": [],          # optional
+                    "teardown_hooks": []        # optional
+                }
+
+        Raises:
+            exceptions.ParamsError
+            exceptions.ValidationFailure
+            exceptions.ExtractFailure
+
         """
         # check skip
-        self._handle_skip_feature(testcase_dict)
+        self._handle_skip_feature(teststep_dict)
 
         # prepare
-        parsed_request = self.init_config(testcase_dict, level="testcase")
-        self.context.bind_testcase_variable("request", parsed_request)
+        extractors = teststep_dict.pop("extract", []) or teststep_dict.pop("extractors", [])
+        validators = teststep_dict.pop("validate", []) or teststep_dict.pop("validators", [])
+        parsed_request = self.init_config(teststep_dict, level="teststep")
+        self.context.update_teststep_variables_mapping("request", parsed_request)
 
         # setup hooks
-        setup_hooks = testcase_dict.get("setup_hooks", [])
+        setup_hooks = teststep_dict.get("setup_hooks", [])
         setup_hooks.insert(0, "${setup_hook_prepare_kwargs($request)}")
         self.do_hook_actions(setup_hooks)
 
@@ -171,21 +202,19 @@ class Runner(object):
         resp_obj = response.ResponseObject(resp)
 
         # teardown hooks
-        teardown_hooks = testcase_dict.get("teardown_hooks", [])
+        teardown_hooks = teststep_dict.get("teardown_hooks", [])
         if teardown_hooks:
             logger.log_info("start to run teardown hooks")
-            self.context.bind_testcase_variable("response", resp_obj)
+            self.context.update_teststep_variables_mapping("response", resp_obj)
             self.do_hook_actions(teardown_hooks)
 
         # extract
-        extractors = testcase_dict.get("extract", []) or testcase_dict.get("extractors", [])
         extracted_variables_mapping = resp_obj.extract_response(extractors)
-        self.context.bind_extracted_variables(extracted_variables_mapping)
+        self.context.update_testcase_runtime_variables_mapping(extracted_variables_mapping)
 
         # validate
-        validators = testcase_dict.get("validate", []) or testcase_dict.get("validators", [])
         try:
-            self.context.validate(validators, resp_obj)
+            self.evaluated_validators = self.context.validate(validators, resp_obj)
         except (exceptions.ParamsError, \
                 exceptions.ValidationFailure, exceptions.ExtractFailure):
             # log request
@@ -207,7 +236,7 @@ class Runner(object):
     def extract_output(self, output_variables_list):
         """ extract output variables
         """
-        variables_mapping = self.context.testcase_variables_mapping
+        variables_mapping = self.context.teststep_variables_mapping
 
         output = {}
         for variable in output_variables_list:
diff --git a/httprunner/utils.py b/httprunner/utils.py
index d12cb2be..395a70c7 100644
--- a/httprunner/utils.py
+++ b/httprunner/utils.py
@@ -267,7 +267,7 @@ def add_teststep(test_runner, teststep_dict):
         finally:
             if hasattr(test_runner.http_client_session, "meta_data"):
                 self.meta_data = test_runner.http_client_session.meta_data
-                self.meta_data["validators"] = test_runner.context.evaluated_validators
+                self.meta_data["validators"] = test_runner.evaluated_validators
                 test_runner.http_client_session.init_meta_data()
 
     test.__doc__ = teststep_dict["name"]
@@ -331,6 +331,8 @@ def print_io(in_out):
     def prepare_content(var_type, in_out):
         content = ""
         for variable, value in in_out.items():
+            if isinstance(value, tuple):
+                continue
 
             if is_py2:
                 if isinstance(variable, unicode):
diff --git a/tests/test_api.py b/tests/test_api.py
index 7115893d..064043ad 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -303,26 +303,26 @@ class TestHttpRunner(ApiServerUnittest):
         self.assertTrue(summary["success"])
         self.assertEqual(len(summary["details"]), 1)
 
-    def test_run_testset_output(self):
+    def test_run_testcase_output(self):
         testcase_file_path = os.path.join(
             os.getcwd(), 'tests/data/demo_testset_layer.yml')
-        runner = HttpRunner().run(testcase_file_path)
+        runner = HttpRunner(failfast=True).run(testcase_file_path)
         summary = runner.summary
         self.assertTrue(summary["success"])
         self.assertIn("token", summary["details"][0]["in_out"]["out"])
         self.assertIn("user_agent", summary["details"][0]["in_out"]["in"])
 
-    def test_run_testset_with_variables_mapping(self):
+    def test_run_testcase_with_variables_mapping(self):
         testcase_file_path = os.path.join(
             os.getcwd(), 'tests/data/demo_testset_layer.yml')
         variables_mapping = {
             "app_version": '2.9.7'
         }
-        runner = HttpRunner().run(testcase_file_path, mapping=variables_mapping)
+        runner = HttpRunner(failfast=True).run(testcase_file_path, mapping=variables_mapping)
         summary = runner.summary
         self.assertTrue(summary["success"])
         self.assertIn("token", summary["details"][0]["in_out"]["out"])
-        self.assertEqual(len(summary["details"][0]["in_out"]["in"]), 7)
+        self.assertEqual(len(summary["details"][0]["in_out"]["in"]), 9)
 
     def test_run_testset_with_parameters(self):
         testcase_file_path = os.path.join(
@@ -340,11 +340,6 @@ class TestHttpRunner(ApiServerUnittest):
         self.assertEqual(hrunner.project_mapping["env"]["PROJECT_KEY"], "ABCDEFGH")
         self.assertIn("debugtalk", hrunner.project_mapping)
         self.assertIn("setup_and_reset", hrunner.project_mapping["def-testcase"])
-        self.assertEqual(
-            hrunner.project_mapping["debugtalk"]["variables"]["SECRET_KEY"],
-            "DebugTalk"
-        )
-        self.assertIn("get_sign", hrunner.project_mapping["debugtalk"]["functions"])
         self.assertIn("get_token", hrunner.project_mapping["def-api"])
         self.assertIn("setup_and_reset", hrunner.project_mapping["def-testcase"])
 
diff --git a/tests/test_context.py b/tests/test_context.py
index bdc322ee..f1ce57e5 100644
--- a/tests/test_context.py
+++ b/tests/test_context.py
@@ -1,201 +1,152 @@
 import os
 import time
-import unittest
 
 import requests
-from httprunner import context, exceptions, loader, parser, response, runner
+from httprunner import context, exceptions, loader, response
 from tests.base import ApiServerUnittest
 
 
 class TestContext(ApiServerUnittest):
 
     def setUp(self):
-        self.context = context.Context()
+        project_dir = os.path.join(os.getcwd(), "tests")
+        loader.load_project_tests(project_dir)
+        loader.load_debugtalk_module(project_dir)
+        self.debugtalk_module = loader.project_mapping["debugtalk"]
+
+        self.context = context.Context(
+            self.debugtalk_module["variables"],
+            self.debugtalk_module["functions"]
+        )
         testcase_file_path = os.path.join(os.getcwd(), 'tests/data/demo_binds.yml')
         self.testcases = loader.load_file(testcase_file_path)
 
-    def test_context_init_functions(self):
-        self.assertIn("get_timestamp", self.context.testset_functions_config)
-        self.assertIn("gen_random_string", self.context.testset_functions_config)
+    def test_init_context_functions(self):
+        context_functions = self.context.TESTCASE_SHARED_FUNCTIONS_MAPPING
+        self.assertIn("gen_md5", context_functions)
+        self.assertIn("equals", context_functions)
 
+    def test_init_context_variables(self):
+        self.assertEqual(
+            self.context.teststep_variables_mapping["SECRET_KEY"],
+            "DebugTalk"
+        )
+        self.assertEqual(
+            self.context.testcase_runtime_variables_mapping["SECRET_KEY"],
+            "DebugTalk"
+        )
+
+    def test_update_context_testcase_level(self):
         variables = [
-            {"random": "${gen_random_string(5)}"},
-            {"timestamp10": "${get_timestamp(10)}"}
+            {"TOKEN": "debugtalk"},
+            {"data": '{"name": "user", "password": "123456"}'}
         ]
-        self.context.bind_variables(variables)
-        context_variables = self.context.testcase_variables_mapping
+        self.context.update_context_variables(variables, "testcase")
+        self.assertEqual(
+            self.context.teststep_variables_mapping["TOKEN"],
+            "debugtalk"
+        )
+        self.assertEqual(
+            self.context.testcase_runtime_variables_mapping["TOKEN"],
+            "debugtalk"
+        )
 
-        self.assertEqual(len(context_variables["random"]), 5)
-        self.assertEqual(len(context_variables["timestamp10"]), 10)
-
-    def test_context_bind_testset_variables(self):
-        # testcase in JSON format
-        testcase1 = {
-            "variables": [
-                {"GLOBAL_TOKEN": "debugtalk"},
-                {"token": "$GLOBAL_TOKEN"}
-            ]
-        }
-        # testcase in YAML format
-        testcase2 = self.testcases["bind_variables"]
-
-        for testcase in [testcase1, testcase2]:
-            variables = testcase['variables']
-            self.context.bind_variables(variables, level="testset")
-
-            testset_variables = self.context.testset_shared_variables_mapping
-            testcase_variables = self.context.testcase_variables_mapping
-            self.assertIn("GLOBAL_TOKEN", testset_variables)
-            self.assertIn("GLOBAL_TOKEN", testcase_variables)
-            self.assertEqual(testset_variables["GLOBAL_TOKEN"], "debugtalk")
-            self.assertIn("token", testset_variables)
-            self.assertIn("token", testcase_variables)
-            self.assertEqual(testset_variables["token"], "debugtalk")
-
-    def test_context_bind_testcase_variables(self):
-        testcase1 = {
-            "variables": [
-                {"GLOBAL_TOKEN": "debugtalk"},
-                {"token": "$GLOBAL_TOKEN"}
-            ]
-        }
-        testcase2 = self.testcases["bind_variables"]
-
-        for testcase in [testcase1, testcase2]:
-            variables = testcase['variables']
-            self.context.bind_variables(variables)
-
-            testset_variables = self.context.testset_shared_variables_mapping
-            testcase_variables = self.context.testcase_variables_mapping
-            self.assertNotIn("GLOBAL_TOKEN", testset_variables)
-            self.assertIn("GLOBAL_TOKEN", testcase_variables)
-            self.assertEqual(testcase_variables["GLOBAL_TOKEN"], "debugtalk")
-            self.assertNotIn("token", testset_variables)
-            self.assertIn("token", testcase_variables)
-            self.assertEqual(testcase_variables["token"], "debugtalk")
-
-    def test_context_bind_lambda_functions(self):
-        function_binds = {
-            "add_one": lambda x: x + 1,
-            "add_two_nums": lambda x, y: x + y
-        }
+    def test_update_context_teststep_level(self):
         variables = [
-            {"add1": "${add_one(2)}"},
-            {"sum2nums": "${add_two_nums(2,3)}"}
+            {"TOKEN": "debugtalk"},
+            {"data": '{"name": "user", "password": "123456"}'}
         ]
-        self.context.bind_functions(function_binds)
-        self.context.bind_variables(variables)
+        self.context.update_context_variables(variables, "teststep")
+        self.assertEqual(
+            self.context.teststep_variables_mapping["TOKEN"],
+            "debugtalk"
+        )
+        self.assertNotIn(
+            "TOKEN",
+            self.context.testcase_runtime_variables_mapping
+        )
 
-        context_variables = self.context.testcase_variables_mapping
-        self.assertIn("add1", context_variables)
-        self.assertEqual(context_variables["add1"], 3)
-        self.assertIn("sum2nums", context_variables)
-        self.assertEqual(context_variables["sum2nums"], 5)
+    def test_eval_content_functions(self):
+        content = "${sleep_N_secs(1)}"
+        start_time = time.time()
+        self.context.eval_content(content)
+        elapsed_time = time.time() - start_time
+        self.assertGreater(elapsed_time, 1)
 
-    def test_call_builtin_functions(self):
-        testcase1 = {
-            "variables": [
-                {"length": "${len(debugtalk)}"},
-                {"smallest": "${min(2, 3, 8)}"},
-                {"largest": "${max(2, 3, 8)}"}
-            ]
-        }
-        testcase2 = self.testcases["builtin_functions"]
+    def test_eval_content_variables(self):
+        content = "abc$SECRET_KEY"
+        self.assertEqual(
+            self.context.eval_content(content),
+            "abcDebugTalk"
+        )
 
-        for testcase in [testcase1, testcase2]:
-            variables = testcase['variables']
-            self.context.bind_variables(variables)
+        # TODO: fix variable extraction
+        # content = "abc$SECRET_KEYdef"
+        # self.assertEqual(
+        #     self.context.eval_content(content),
+        #     "abcDebugTalkdef"
+        # )
 
-            context_variables = self.context.testcase_variables_mapping
-            self.assertEqual(context_variables["length"], 9)
-            self.assertEqual(context_variables["smallest"], 2)
-            self.assertEqual(context_variables["largest"], 8)
+    def test_update_testcase_runtime_variables_mapping(self):
+        variables = {"abc": 123}
+        self.context.update_testcase_runtime_variables_mapping(variables)
+        self.assertEqual(
+            self.context.testcase_runtime_variables_mapping["abc"],
+            123
+        )
+        self.assertEqual(
+            self.context.teststep_variables_mapping["abc"],
+            123
+        )
 
-    def test_import_module_items(self):
+    def test_update_teststep_variables_mapping(self):
+        self.context.update_teststep_variables_mapping("abc", 123)
+        self.assertEqual(
+            self.context.teststep_variables_mapping["abc"],
+            123
+        )
+        self.assertNotIn(
+            "abc",
+            self.context.testcase_runtime_variables_mapping
+        )
+
+    def test_get_parsed_request(self):
         variables = [
             {"TOKEN": "debugtalk"},
             {"random": "${gen_random_string(5)}"},
             {"data": '{"name": "user", "password": "123456"}'},
             {"authorization": "${gen_md5($TOKEN, $data, $random)}"}
         ]
-        from tests import debugtalk
-        from tests.debugtalk import gen_md5
-        self.context.import_module_items(debugtalk)
-        self.context.bind_variables(variables)
-        context_variables = self.context.testcase_variables_mapping
+        self.context.update_context_variables(variables, "teststep")
 
-        self.assertIn("TOKEN", context_variables)
-        TOKEN = context_variables["TOKEN"]
-        self.assertEqual(TOKEN, "debugtalk")
-        self.assertIn("random", context_variables)
-        self.assertIsInstance(context_variables["random"], str)
-        self.assertEqual(len(context_variables["random"]), 5)
-        random = context_variables["random"]
-        self.assertIn("data", context_variables)
-        data = context_variables["data"]
-        self.assertIn("authorization", context_variables)
-        self.assertEqual(len(context_variables["authorization"]), 32)
-        authorization = context_variables["authorization"]
-        self.assertEqual(gen_md5(TOKEN, data, random), authorization)
-        self.assertIn("SECRET_KEY", context_variables)
-        SECRET_KEY = context_variables["SECRET_KEY"]
-        self.assertEqual(SECRET_KEY, "DebugTalk")
-
-    def test_get_parsed_request(self):
-        test_runner = runner.Runner()
-        testcase = {
-            "variables": [
-                {"TOKEN": "debugtalk"},
-                {"random": "${gen_random_string(5)}"},
-                {"data": '{"name": "user", "password": "123456"}'},
-                {"authorization": "${gen_md5($TOKEN, $data, $random)}"}
-            ],
-            "request": {
-                "url": "http://127.0.0.1:5000/api/users/1000",
-                "method": "POST",
-                "headers": {
-                    "Content-Type": "application/json",
-                    "authorization": "$authorization",
-                    "random": "$random",
-                    "secret_key": "$SECRET_KEY"
-                },
-                "data": "$data"
-            }
+        request = {
+            "url": "http://127.0.0.1:5000/api/users/1000",
+            "method": "POST",
+            "headers": {
+                "Content-Type": "application/json",
+                "authorization": "$authorization",
+                "random": "$random",
+                "secret_key": "$SECRET_KEY"
+            },
+            "data": "$data"
         }
-        from tests import debugtalk
-        self.context.import_module_items(debugtalk)
-        self.context.bind_variables(testcase["variables"])
-        parsed_request = self.context.get_parsed_request(testcase["request"])
+        parsed_request = self.context.get_parsed_request(request, level="teststep")
         self.assertIn("authorization", parsed_request["headers"])
         self.assertEqual(len(parsed_request["headers"]["authorization"]), 32)
         self.assertIn("random", parsed_request["headers"])
         self.assertEqual(len(parsed_request["headers"]["random"]), 5)
         self.assertIn("data", parsed_request)
-        self.assertEqual(parsed_request["data"], testcase["variables"][2]["data"])
+        self.assertEqual(parsed_request["data"], variables[2]["data"])
         self.assertEqual(parsed_request["headers"]["secret_key"], "DebugTalk")
 
-    def test_exec_content_functions(self):
-        test_runner = runner.Runner()
-        content = "${sleep_N_secs(1)}"
-        start_time = time.time()
-        test_runner.context.eval_content(content)
-        end_time = time.time()
-        elapsed_time = end_time - start_time
-        self.assertGreater(elapsed_time, 1)
-
     def test_do_validation(self):
-        self.context.do_validation(
+        self.context._do_validation(
             {"check": "check", "check_value": 1, "expect": 1, "comparator": "eq"}
         )
-        self.context.do_validation(
+        self.context._do_validation(
             {"check": "check", "check_value": "abc", "expect": "abc", "comparator": "=="}
         )
-
-        config_dict = {
-            "path": 'tests/data/demo_testset_hardcode.yml'
-        }
-        self.context.config_context(config_dict, "testset")
-        self.context.do_validation(
+        self.context._do_validation(
             {"check": "status_code", "check_value": "201", "expect": 3, "comparator": "sum_status_code"}
         )
 
@@ -213,7 +164,7 @@ class TestContext(ApiServerUnittest):
             {"resp_status_code": 200},
             {"resp_body_success": True}
         ]
-        self.context.bind_variables(variables)
+        self.context.update_context_variables(variables, "teststep")
 
         with self.assertRaises(exceptions.ValidationFailure):
             self.context.validate(validators, resp_obj)
@@ -228,13 +179,7 @@ class TestContext(ApiServerUnittest):
             {"resp_status_code": 201},
             {"resp_body_success": True}
         ]
-        self.context.bind_variables(variables)
-        from tests.debugtalk import is_status_code_200
-        functions = {
-            "is_status_code_200": is_status_code_200
-        }
-        self.context.bind_functions(functions)
-
+        self.context.update_context_variables(variables, "teststep")
         self.context.validate(validators, resp_obj)
 
     def test_validate_exception(self):
@@ -248,7 +193,7 @@ class TestContext(ApiServerUnittest):
             {"check": "$resp_status_code", "comparator": "eq", "expect": 201}
         ]
         variables = []
-        self.context.bind_variables(variables)
+        self.context.update_context_variables(variables, "teststep")
 
         with self.assertRaises(exceptions.VariableNotFound):
             self.context.validate(validators, resp_obj)
@@ -257,294 +202,7 @@ class TestContext(ApiServerUnittest):
         variables = [
             {"resp_status_code": 200}
         ]
-        self.context.bind_variables(variables)
+        self.context.update_context_variables(variables, "teststep")
 
         with self.assertRaises(exceptions.ValidationFailure):
             self.context.validate(validators, resp_obj)
-
-
-class TestTestcaseParser(unittest.TestCase):
-
-    def test_eval_content_variables(self):
-        variables = {
-            "var_1": "abc",
-            "var_2": "def",
-            "var_3": 123,
-            "var_4": {"a": 1},
-            "var_5": True,
-            "var_6": None
-        }
-        testcase_parser = context.TestcaseParser(variables=variables)
-        self.assertEqual(
-            testcase_parser._eval_content_variables("$var_1"),
-            "abc"
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("var_1"),
-            "var_1"
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("$var_1#XYZ"),
-            "abc#XYZ"
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("/$var_1/$var_2/var3"),
-            "/abc/def/var3"
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("/$var_1/$var_2/$var_1"),
-            "/abc/def/abc"
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("${func($var_1, $var_2, xyz)}"),
-            "${func(abc, def, xyz)}"
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("$var_3"),
-            123
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("$var_4"),
-            {"a": 1}
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("$var_5"),
-            True
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("abc$var_5"),
-            "abcTrue"
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("abc$var_4"),
-            "abc{'a': 1}"
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_variables("$var_6"),
-            None
-        )
-
-    def test_eval_content_variables_search_upward(self):
-        testcase_parser = context.TestcaseParser()
-
-        with self.assertRaises(exceptions.VariableNotFound):
-            testcase_parser._eval_content_variables("/api/$SECRET_KEY")
-
-        testcase_parser.file_path = "tests/data/demo_testset_hardcode.yml"
-        content = testcase_parser._eval_content_variables("/api/$SECRET_KEY")
-        self.assertEqual(content, "/api/DebugTalk")
-
-
-    def test_parse_content_with_bindings_variables(self):
-        variables = {
-            "str_1": "str_value1",
-            "str_2": "str_value2"
-        }
-        testcase_parser = context.TestcaseParser(variables=variables)
-        self.assertEqual(
-            testcase_parser.eval_content_with_bindings("$str_1"),
-            "str_value1"
-        )
-        self.assertEqual(
-            testcase_parser.eval_content_with_bindings("123$str_1/456"),
-            "123str_value1/456"
-        )
-
-        with self.assertRaises(exceptions.VariableNotFound):
-            testcase_parser.eval_content_with_bindings("$str_3")
-
-        self.assertEqual(
-            testcase_parser.eval_content_with_bindings(["$str_1", "str3"]),
-            ["str_value1", "str3"]
-        )
-        self.assertEqual(
-            testcase_parser.eval_content_with_bindings({"key": "$str_1"}),
-            {"key": "str_value1"}
-        )
-
-    def test_parse_content_with_bindings_multiple_identical_variables(self):
-        variables = {
-            "userid": 100,
-            "data": 1498
-        }
-        testcase_parser = context.TestcaseParser(variables=variables)
-        content = "/users/$userid/training/$data?userId=$userid&data=$data"
-        self.assertEqual(
-            testcase_parser.eval_content_with_bindings(content),
-            "/users/100/training/1498?userId=100&data=1498"
-        )
-
-    def test_parse_variables_multiple_identical_variables(self):
-        variables = {
-            "user": 100,
-            "userid": 1000,
-            "data": 1498
-        }
-        testcase_parser = context.TestcaseParser(variables=variables)
-        content = "/users/$user/$userid/$data?userId=$userid&data=$data"
-        self.assertEqual(
-            testcase_parser.eval_content_with_bindings(content),
-            "/users/100/1000/1498?userId=1000&data=1498"
-        )
-
-    def test_parse_content_with_bindings_functions(self):
-        import random, string
-        functions = {
-            "gen_random_string": lambda str_len: ''.join(random.choice(string.ascii_letters + string.digits) \
-                for _ in range(str_len))
-        }
-        testcase_parser = context.TestcaseParser(functions=functions)
-
-        result = testcase_parser.eval_content_with_bindings("${gen_random_string(5)}")
-        self.assertEqual(len(result), 5)
-
-        add_two_nums = lambda a, b=1: a + b
-        functions["add_two_nums"] = add_two_nums
-        self.assertEqual(
-            testcase_parser.eval_content_with_bindings("${add_two_nums(1)}"),
-            2
-        )
-        self.assertEqual(
-            testcase_parser.eval_content_with_bindings("${add_two_nums(1, 2)}"),
-            3
-        )
-
-    def test_eval_content_functions(self):
-        functions = {
-            "add_two_nums": lambda a, b=1: a + b
-        }
-        testcase_parser = context.TestcaseParser(functions=functions)
-        self.assertEqual(
-            testcase_parser._eval_content_functions("${add_two_nums(1, 2)}"),
-            3
-        )
-        self.assertEqual(
-            testcase_parser._eval_content_functions("/api/${add_two_nums(1, 2)}"),
-            "/api/3"
-        )
-
-    def test_eval_content_functions_search_upward(self):
-        testcase_parser = context.TestcaseParser()
-
-        with self.assertRaises(exceptions.FunctionNotFound):
-            testcase_parser._eval_content_functions("/api/${gen_md5(abc)}")
-
-        testcase_parser.file_path = "tests/data/demo_testset_hardcode.yml"
-        content = testcase_parser._eval_content_functions("/api/${gen_md5(abc)}")
-        self.assertEqual(content, "/api/900150983cd24fb0d6963f7d28e17f72")
-
-    def test_parse_content_with_bindings_testcase(self):
-        variables = {
-            "uid": "1000",
-            "random": "A2dEx",
-            "authorization": "a83de0ff8d2e896dbd8efb81ba14e17d",
-            "data": {"name": "user", "password": "123456"}
-        }
-        functions = {
-            "add_two_nums": lambda a, b=1: a + b,
-            "get_timestamp": lambda: int(time.time() * 1000)
-        }
-        testcase_template = {
-            "url": "http://127.0.0.1:5000/api/users/$uid/${add_two_nums(1,2)}",
-            "method": "POST",
-            "headers": {
-                "Content-Type": "application/json",
-                "authorization": "$authorization",
-                "random": "$random",
-                "sum": "${add_two_nums(1, 2)}"
-            },
-            "body": "$data"
-        }
-        parsed_testcase = context.TestcaseParser(variables, functions)\
-            .eval_content_with_bindings(testcase_template)
-
-        self.assertEqual(
-            parsed_testcase["url"],
-            "http://127.0.0.1:5000/api/users/1000/3"
-        )
-        self.assertEqual(
-            parsed_testcase["headers"]["authorization"],
-            variables["authorization"]
-        )
-        self.assertEqual(
-            parsed_testcase["headers"]["random"],
-            variables["random"]
-        )
-        self.assertEqual(
-            parsed_testcase["body"],
-            variables["data"]
-        )
-        self.assertEqual(
-            parsed_testcase["headers"]["sum"],
-            3
-        )
-
-    def test_parse_parameters_raw_list(self):
-        parameters = [
-            {"user_agent": ["iOS/10.1", "iOS/10.2", "iOS/10.3"]},
-            {"username-password": [("user1", "111111"), ["test2", "222222"]]}
-        ]
-        cartesian_product_parameters = context.parse_parameters(parameters)
-        self.assertEqual(
-            len(cartesian_product_parameters),
-            3 * 2
-        )
-        self.assertEqual(
-            cartesian_product_parameters[0],
-            {'user_agent': 'iOS/10.1', 'username': 'user1', 'password': '111111'}
-        )
-
-    def test_parse_parameters_parameterize(self):
-        parameters = [
-            {"app_version": "${parameterize(app_version.csv)}"},
-            {"username-password": "${parameterize(account.csv)}"}
-        ]
-        testset_path = os.path.join(
-            os.getcwd(),
-            "tests/data/demo_parameters.yml"
-        )
-        cartesian_product_parameters = context.parse_parameters(
-            parameters,
-            testset_path
-        )
-        self.assertEqual(
-            len(cartesian_product_parameters),
-            2 * 3
-        )
-
-    def test_parse_parameters_custom_function(self):
-        parameters = [
-            {"app_version": "${gen_app_version()}"},
-            {"username-password": "${get_account()}"}
-        ]
-        testset_path = os.path.join(
-            os.getcwd(),
-            "tests/data/demo_parameters.yml"
-        )
-        cartesian_product_parameters = context.parse_parameters(
-            parameters,
-            testset_path
-        )
-        self.assertEqual(
-            len(cartesian_product_parameters),
-            2 * 2
-        )
-
-    def test_parse_parameters_mix(self):
-        parameters = [
-            {"user_agent": ["iOS/10.1", "iOS/10.2", "iOS/10.3"]},
-            {"app_version": "${gen_app_version()}"},
-            {"username-password": "${parameterize(account.csv)}"}
-        ]
-        testset_path = os.path.join(
-            os.getcwd(),
-            "tests/data/demo_parameters.yml"
-        )
-        cartesian_product_parameters = context.parse_parameters(
-            parameters,
-            testset_path
-        )
-        self.assertEqual(
-            len(cartesian_product_parameters),
-            3 * 2 * 3
-        )
diff --git a/tests/test_loader.py b/tests/test_loader.py
index 339b718b..af87fb59 100644
--- a/tests/test_loader.py
+++ b/tests/test_loader.py
@@ -180,13 +180,17 @@ class TestModuleLoader(unittest.TestCase):
         self.assertNotIn("is_py3", functions_dict)
 
     def test_load_debugtalk_module(self):
-        imported_module_items = loader.load_debugtalk_module()
+        project_dir = os.path.join(os.getcwd(), "tests")
+        loader.load_project_tests(project_dir)
+        loader.load_debugtalk_module()
+        imported_module_items = loader.project_mapping["debugtalk"]
         self.assertIn("basestring", imported_module_items["variables"])
         self.assertIn("equals", imported_module_items["functions"])
         self.assertNotIn("SECRET_KEY", imported_module_items["variables"])
         self.assertNotIn("alter_response", imported_module_items["functions"])
 
-        imported_module_items = loader.load_debugtalk_module("tests")
+        loader.load_debugtalk_module("tests")
+        imported_module_items = loader.project_mapping["debugtalk"]
         self.assertEqual(
             imported_module_items["variables"]["SECRET_KEY"],
             "DebugTalk"
@@ -476,7 +480,9 @@ class TestSuiteLoader(unittest.TestCase):
 
     def test_load_project_tests(self):
         project_dir = os.path.join(os.getcwd(), "tests")
-        project_tests = loader.load_project_tests(project_dir)
-        self.assertEqual(project_tests["debugtalk"]["variables"]["SECRET_KEY"], "DebugTalk")
-        self.assertIn("get_token", project_tests["def-api"])
-        self.assertIn("setup_and_reset", project_tests["def-testcase"])
+        loader.load_project_tests(project_dir)
+        loader.load_debugtalk_module(project_dir)
+        project_mapping = loader.project_mapping
+        self.assertEqual(project_mapping["debugtalk"]["variables"]["SECRET_KEY"], "DebugTalk")
+        self.assertIn("get_token", project_mapping["def-api"])
+        self.assertIn("setup_and_reset", project_mapping["def-testcase"])
diff --git a/tests/test_runner.py b/tests/test_runner.py
index 475d22ec..1e19c5a0 100644
--- a/tests/test_runner.py
+++ b/tests/test_runner.py
@@ -10,7 +10,15 @@ from tests.base import ApiServerUnittest
 class TestRunner(ApiServerUnittest):
 
     def setUp(self):
-        self.test_runner = runner.Runner()
+        project_dir = os.path.join(os.getcwd(), "tests")
+        loader.load_project_tests(project_dir)
+        loader.load_debugtalk_module(project_dir)
+        self.debugtalk_module = loader.project_mapping["debugtalk"]
+        config_dict = {
+            "variables": self.debugtalk_module["variables"],
+            "functions": self.debugtalk_module["functions"]
+        }
+        self.test_runner = runner.Runner(config_dict)
         self.reset_all()
 
     def reset_all(self):
@@ -30,18 +38,19 @@ class TestRunner(ApiServerUnittest):
             testcases = loader.load_file(testcase_file_path)
 
             config_dict = {
-                "path": testcase_file_path
+                "variables": self.debugtalk_module["variables"],
+                "functions": self.debugtalk_module["functions"]
             }
-            self.test_runner.init_config(config_dict, "testset")
+            test_runner = runner.Runner(config_dict)
 
             test = testcases[0]["test"]
-            self.test_runner.run_test(test)
+            test_runner.run_test(test)
 
             test = testcases[1]["test"]
-            self.test_runner.run_test(test)
+            test_runner.run_test(test)
 
             test = testcases[2]["test"]
-            self.test_runner.run_test(test)
+            test_runner.run_test(test)
 
     def test_run_single_testcase_fail(self):
         test = {
@@ -75,6 +84,8 @@ class TestRunner(ApiServerUnittest):
         config_dict = {
             "path": os.path.join(os.getcwd(), __file__),
             "name": "basic test with httpbin",
+            "variables": self.debugtalk_module["variables"],
+            "functions": self.debugtalk_module["functions"],
             "request": {
                 "base_url": HTTPBIN_SERVER
             },
@@ -123,6 +134,8 @@ class TestRunner(ApiServerUnittest):
         config_dict = {
             "path": os.path.join(os.getcwd(), __file__),
             "name": "basic test with httpbin",
+            "variables": self.debugtalk_module["variables"],
+            "functions": self.debugtalk_module["functions"],
             "request": {
                 "base_url": HTTPBIN_SERVER
             }
@@ -177,7 +190,7 @@ class TestRunner(ApiServerUnittest):
         config_dict = {
             "path": os.path.join(os.getcwd(), __file__)
         }
-        self.test_runner.init_config(config_dict, "testset")
+        self.test_runner.init_config(config_dict, "testcase")
 
         start_time = time.time()
         self.test_runner.run_test(test)
@@ -210,7 +223,7 @@ class TestRunner(ApiServerUnittest):
         config_dict = {
             "path": os.path.join(os.getcwd(), __file__)
         }
-        self.test_runner.init_config(config_dict, "testset")
+        self.test_runner.init_config(config_dict, "testcase")
 
         start_time = time.time()
         self.test_runner.run_test(test)
@@ -238,7 +251,7 @@ class TestRunner(ApiServerUnittest):
         config_dict = {
             "path": testcase_file_path
         }
-        self.test_runner.init_config(config_dict, "testset")
+        self.test_runner.init_config(config_dict, "testcase")
 
         test = testcases[2]["test"]
         self.test_runner.run_test(test)