diff --git a/httprunner/client.py b/httprunner/client.py
index 0644b0bc..0f9e4d9a 100644
--- a/httprunner/client.py
+++ b/httprunner/client.py
@@ -115,7 +115,7 @@ class HttpSession(requests.Session):
         def log_print(request_response):
             msg = "\n================== {} details ==================\n".format(request_response)
             for key, value in self.meta_data[request_response].items():
-                msg += "{:<16} : {}\n".format(key, value)
+                msg += "{:<16} : {}\n".format(key, repr(value))
             logger.log_debug(msg)
 
         # record original request info
diff --git a/httprunner/context.py b/httprunner/context.py
index e4799c8c..59734b29 100644
--- a/httprunner/context.py
+++ b/httprunner/context.py
@@ -261,6 +261,10 @@ class Context(object):
     def validate(self, validators, resp_obj):
         """ make validations
         """
+        if not validators:
+            return
+
+        logger.log_info("start to validate.")
         self.evaluated_validators = []
         validate_pass = True
 
diff --git a/httprunner/runner.py b/httprunner/runner.py
index 12c31b13..9f38f1a7 100644
--- a/httprunner/runner.py
+++ b/httprunner/runner.py
@@ -197,14 +197,14 @@ class Runner(object):
             err_req_msg = "request: \n"
             err_req_msg += "headers: {}\n".format(parsed_request.pop("headers", {}))
             for k, v in parsed_request.items():
-                err_req_msg += "{}: {}\n".format(k, v)
+                err_req_msg += "{}: {}\n".format(k, repr(v))
             logger.log_error(err_req_msg)
 
             # log response
             err_resp_msg = "response: \n"
             err_resp_msg += "status_code: {}\n".format(resp_obj.status_code)
             err_resp_msg += "headers: {}\n".format(resp_obj.headers)
-            err_resp_msg += "content: {}\n".format(resp_obj.content)
+            err_resp_msg += "content: {}\n".format(repr(resp_obj.text))
             logger.log_error(err_resp_msg)
 
             raise
diff --git a/httprunner/task.py b/httprunner/task.py
index 44004c8e..437ae6d3 100644
--- a/httprunner/task.py
+++ b/httprunner/task.py
@@ -26,7 +26,7 @@ class TestCase(unittest.TestCase):
         try:
             self.test_runner.run_test(self.testcase_dict)
         except exceptions.MyBaseFailure as ex:
-            self.fail(str(ex))
+            self.fail(repr(ex))
         finally:
             if hasattr(self.test_runner.http_client_session, "meta_data"):
                 self.meta_data = self.test_runner.http_client_session.meta_data
diff --git a/httprunner/testcase.py b/httprunner/testcase.py
index ac4fef16..b7a52a2e 100644
--- a/httprunner/testcase.py
+++ b/httprunner/testcase.py
@@ -10,7 +10,8 @@ import random
 import re
 
 from httprunner import exceptions, logger, utils
-from httprunner.compat import OrderedDict, basestring, numeric_types
+from httprunner.compat import (OrderedDict, basestring, builtin_str,
+                               numeric_types, str)
 from httprunner.utils import FileUtils
 
 variable_regexp = r"\$([\w_]+)"
@@ -627,7 +628,9 @@ def substitute_variables_with_mapping(content, mapping):
             # content is a variable
             content = value
         else:
-            content = content.replace(var, str(value))
+            if not isinstance(value, str):
+                value = builtin_str(value)
+            content = content.replace(var, value)
 
     return content
 
@@ -850,9 +853,12 @@ class TestcaseParser(object):
                 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),
-                    str(variable_value), 1
+                    variable_value, 1
                 )
 
         return content