diff --git a/examples/variables_test.go b/examples/variables_test.go
index f3df328a..5ce4262c 100644
--- a/examples/variables_test.go
+++ b/examples/variables_test.go
@@ -109,3 +109,50 @@ func TestCaseOverrideConfigVariables(t *testing.T) {
 		t.Fatalf("run testcase error: %v", err)
 	}
 }
+
+func TestCaseParseVariables(t *testing.T) {
+	testcase := &httpboomer.TestCase{
+		Config: httpboomer.TConfig{
+			Name:    "run request with functions",
+			BaseURL: "https://postman-echo.com",
+			Verify:  false,
+			Variables: map[string]interface{}{
+				"n":       5,
+				"a":       12.3,
+				"b":       3.45,
+				"varFoo1": "${gen_random_string($n)}",
+				"varFoo2": "${max($a, $b)}", // 12.3
+			},
+		},
+		TestSteps: []httpboomer.IStep{
+			httpboomer.Step("get with params").
+				WithVariables(map[string]interface{}{
+					"n":       3,
+					"b":       34.5,
+					"varFoo2": "${max($a, $b)}", // 34.5
+				}).
+				GET("/get").
+				WithParams(map[string]interface{}{"foo1": "$varFoo1", "foo2": "$varFoo2"}).
+				WithHeaders(map[string]string{"User-Agent": "HttpBoomer"}).
+				Extract().
+				WithJmesPath("body.args.foo1", "varFoo1").
+				Validate().
+				AssertEqual("status_code", 200, "check status code").
+				AssertLengthEqual("body.args.foo1", 5, "check args foo1").
+				AssertEqual("body.args.foo2", "34.5", "check args foo2"), // notice: request params value will be converted to string
+			httpboomer.Step("post json data with functions").
+				POST("/post").
+				WithHeaders(map[string]string{"User-Agent": "HttpBoomer"}).
+				WithJSON(map[string]interface{}{"foo1": "${gen_random_string($n)}", "foo2": "${max($a, $b)}"}).
+				Validate().
+				AssertEqual("status_code", 200, "check status code").
+				AssertLengthEqual("body.json.foo1", 5, "check args foo1").
+				AssertEqual("body.json.foo2", 12.3, "check args foo2"),
+		},
+	}
+
+	err := httpboomer.Test(t, testcase)
+	if err != nil {
+		t.Fatalf("run testcase error: %v", err)
+	}
+}
diff --git a/parser_test.go b/parser_test.go
index aacb5c64..a1f735e3 100644
--- a/parser_test.go
+++ b/parser_test.go
@@ -264,21 +264,28 @@ func TestParseHeaders(t *testing.T) {
 }
 
 func TestMergeVariables(t *testing.T) {
-	stepVariables := map[string]interface{}{
-		"base_url": "$base_url",
-		"foo1":     "bar1",
+	testData := []struct {
+		stepVariables   map[string]interface{}
+		configVariables map[string]interface{}
+		expectVariables map[string]interface{}
+	}{
+		{
+			map[string]interface{}{"base_url": "$base_url", "foo1": "bar1"},
+			map[string]interface{}{"base_url": "https://httpbin.org", "foo1": "bar111"},
+			map[string]interface{}{"base_url": "https://httpbin.org", "foo1": "bar1"},
+		},
+		{
+			map[string]interface{}{"n": 3, "b": 34.5, "varFoo2": "${max($a, $b)}"},
+			map[string]interface{}{"n": 5, "a": 12.3, "b": 3.45, "varFoo1": "7a6K3", "varFoo2": 12.3},
+			map[string]interface{}{"n": 3, "a": 12.3, "b": 34.5, "varFoo1": "7a6K3", "varFoo2": "${max($a, $b)}"},
+		},
 	}
-	configVariables := map[string]interface{}{
-		"base_url": "https://httpbin.org",
-		"foo1":     "bar111",
-	}
-	mergedVariables := mergeVariables(stepVariables, configVariables)
-	expectVariables := map[string]interface{}{
-		"base_url": "https://httpbin.org",
-		"foo1":     "bar1",
-	}
-	if !assert.Equal(t, expectVariables, mergedVariables) {
-		t.Fail()
+
+	for _, data := range testData {
+		mergedVariables := mergeVariables(data.stepVariables, data.configVariables)
+		if !assert.Equal(t, data.expectVariables, mergedVariables) {
+			t.Fail()
+		}
 	}
 }
 
@@ -439,6 +446,10 @@ func TestParseVariables(t *testing.T) {
 			map[string]interface{}{"varA": "$varB", "varB": "$varC", "varC": "123", "a": 1, "b": 2},
 			map[string]interface{}{"varA": "123", "varB": "123", "varC": "123", "a": 1, "b": 2},
 		},
+		{
+			map[string]interface{}{"n": 34.5, "a": 12.3, "b": "$n", "varFoo2": "${max($a, $b)}"},
+			map[string]interface{}{"n": 34.5, "a": 12.3, "b": 34.5, "varFoo2": 34.5},
+		},
 	}
 
 	for _, data := range testData {