Now, we will write a first round of unit tests. Specifically, we will write unit tests related to the LED resources. Create a new tests subfolder within the virtual environment's root folder. Then, create a new test_hexacopter.py file within the new tests subfolder. Add the following lines that declare many import statements and the TextHexacopter class. The code file for the sample is included in the restful_python_chapter_10_02 folder:

import unittest 
import status 
import json 
from tornado import ioloop, escape 
from tornado.testing import AsyncHTTPTestCase, gen_test, gen 
from async_api import Application 
 
 
class TestHexacopter(AsyncHTTPTestCase): 
    def get_app(self): 
        self.app = Application(debug=False) 
        return self.app 
 
    def test_set_and_get_led_brightness_level(self): 
        """ 
        Ensure we can set and get the brightness levels for both LEDs 
        """ 
        patch_args_led_1 = {'brightness_level': 128} 
        patch_args_led_2 = {'brightness_level': 250} 
        patch_response_led_1 = self.fetch( 
            '/leds/1',  
            method='PATCH',  
            body=json.dumps(patch_args_led_1)) 
        patch_response_led_2 = self.fetch( 
            '/leds/2',  
            method='PATCH',  
            body=json.dumps(patch_args_led_2)) 
        self.assertEqual(patch_response_led_1.code, status.HTTP_200_OK) 
        self.assertEqual(patch_response_led_2.code, status.HTTP_200_OK) 
        get_response_led_1 = self.fetch( 
            '/leds/1', 
            method='GET') 
        get_response_led_2 = self.fetch( 
            '/leds/2', 
            method='GET') 
        self.assertEqual(get_response_led_1.code, status.HTTP_200_OK) 
        self.assertEqual(get_response_led_2.code, status.HTTP_200_OK) 
        get_response_led_1_data = escape.json_decode(get_response_led_1.body) 
        get_response_led_2_data = escape.json_decode(get_response_led_2.body) 
        self.assertTrue('brightness_level' in get_response_led_1_data.keys()) 
        self.assertTrue('brightness_level' in get_response_led_2_data.keys()) 
        self.assertEqual(get_response_led_1_data['brightness_level'],  
                         patch_args_led_1['brightness_level']) 
        self.assertEqual(get_response_led_2_data['brightness_level'],  
                         patch_args_led_2['brightness_level']) 

The TestHexacopter class is a subclass of tornado.testing.AsyncHTTPTestCase, that is, a test case that starts up a Tornado HTTP Server. The class overrides the get_app method that returns the tornado.web.Application instance that we want to test. In this case, we return an instance of the Application class declared in the async_api module, with the debug argument set to False.

The test_set_and_get_led_brightness_level method tests whether we can set and get the brightness levels for both the white and blue LED. The code composes and sends two HTTP PATCH methods to set new brightness level values for the LEDs whose IDs are equal to 1 and 2. The code sets a different brightness level for each LED.

The code calls the self.fetch method to compose and send the HTTP PATCH request and calls json.dumps with the dictionary to be sent to the body as an argument. Then, the code uses self.fetch again to compose and send two HTTP GET methods to retrieve the brightness level values for the LEDs whose brightness values have been modified. The code uses tornado.escape.json_decode to convert the bytes in the response body to a Python dictionary. The method uses assertEqual and assertTrue to check for the following expected results: