util: extract IsError method

pkg/exchange/max/maxapi/restapi.go

@@ -274,7 +274,7 @@ func (c *RestClient) sendRequest(req *http.Request) (*util.Response, error) {
 	}
 
 	// Check error, if there is an error, return the ErrorResponse struct type
-	if isError(response) {
+	if response.IsError() {
 		errorResponse, err := toErrorResponse(response)
 		if err != nil {
 			return response, err
@@ -359,12 +359,6 @@ func (r *ErrorResponse) Error() string {
 	)
 }
 
-// isError check the response status code so see if a response is an error.
-func isError(response *util.Response) bool {
-	var c = response.StatusCode
-	return c < 200 || c > 299
-}
-
 // toErrorResponse tries to convert/parse the server response to the standard Error interface object
 func toErrorResponse(response *util.Response) (errorResponse *ErrorResponse, err error) {
 	errorResponse = &ErrorResponse{Response: response}

pkg/util/http_response.go

@@ -36,3 +36,7 @@ func (r *Response) String() string {
 func (r *Response) DecodeJSON(o interface{}) error {
 	return json.Unmarshal(r.Body, o)
 }
+
+func (r *Response) IsError() bool {
+	return r.StatusCode >= 400
+}

pkg/util/http_response_test.go

@@ -26,3 +26,19 @@ func TestResponse_DecodeJSON(t *testing.T) {
 	assert.NoError(t, resp.DecodeJSON(&result))
 	assert.Equal(t, "Test Name", result.Name)
 }
+
+func TestResponse_IsError(t *testing.T) {
+	resp := &Response{Response: &http.Response{}}
+	cases := map[int]bool{
+		100: false,
+		200: false,
+		300: false,
+		400: true,
+		500: true,
+	}
+
+	for code, isErr := range cases {
+		resp.StatusCode = code
+		assert.Equal(t, isErr, resp.IsError())
+	}
+}