Refactor JSON type mismatch error handling tests for clarity and reliability

Author: moutonjeremy

json_type_error_test.go

@@ -18,11 +18,14 @@ import (
 // the raw Go error message is not user-friendly:
 //   "json: cannot unmarshal number into Go struct field Request.Description of type string"
 //
-// Solution: Detect json.UnmarshalTypeError and transform it into a readable message:
+// Solution: Parse the error message to extract field name and type information,
+// then transform it into a readable message:
 //   "invalid type for field 'description': expected string but got number"
 //
-// Implementation: Uses errors.As (not type assertion) to handle wrapped errors correctly.
-// This ensures the error detection works even if the error is wrapped by Fiber or middleware.
+// Implementation: The error type from c.BodyParser() is *errors.UnmarshalTypeError
+// (not *json.UnmarshalTypeError), so we parse the error message string to extract
+// the field name, expected type, and actual type. This approach works reliably
+// across different Fiber versions and handles all JSON unmarshal type errors.
 
 // Test for JSON type mismatch errors
 func TestJSONTypeMismatchErrors(t *testing.T) {
@@ -115,48 +118,6 @@ func TestJSONTypeMismatchErrors(t *testing.T) {
 	}
 }
 
-// Test that errors.As correctly handles wrapped errors
-func TestJSONTypeMismatchWithWrappedError(t *testing.T) {
-	app := fiber.New()
-	oapi := New(app)
-
-	type TestRequest struct {
-		Value string `json:"value"`
-	}
-
-	type TestResponse struct {
-		Result string `json:"result"`
-	}
-
-	Post(oapi, "/test", func(c *fiber.Ctx, input TestRequest) (TestResponse, TestError) {
-		return TestResponse{Result: "OK"}, TestError{}
-	}, OpenAPIOptions{})
-
-	// Test with wrong type - even if the error is wrapped, errors.As should detect it
-	req := httptest.NewRequest("POST", "/test", strings.NewReader(`{"value": 123}`))
-	req.Header.Set("Content-Type", "application/json")
-	resp, err := app.Test(req)
-	if err != nil {
-		t.Fatalf("Expected no error, got %v", err)
-	}
-
-	if resp.StatusCode != 400 {
-		t.Errorf("Expected status 400, got %d", resp.StatusCode)
-	}
-
-	body, _ := io.ReadAll(resp.Body)
-	bodyStr := string(body)
-
-	// Should contain our custom error message
-	if !strings.Contains(bodyStr, "invalid type for field 'value'") {
-		t.Errorf("Expected 'invalid type for field' in error message, got %s", bodyStr)
-	}
-
-	if !strings.Contains(bodyStr, "expected string but got number") {
-		t.Errorf("Expected 'expected string but got number' in error message, got %s", bodyStr)
-	}
-}
-
 // Test with custom validation error handler
 func TestJSONTypeMismatchWithCustomHandler(t *testing.T) {
 	app := fiber.New()