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Testing RESTful Routes

Slides

Starter Code

Agenda

  1. Learning Objectives
  2. Why Test Our Routes?
  3. Forms of Testing
  4. Unit Tests
  5. Break
  6. Route Tests

Learning Objectives

  1. List various types of automated tests
  2. Define unit tests and how to implement them in Python
  3. Implement route tests for one resource

Why Test Our Routes?

What is Automated Testing?

Manual testing means manually running your program many times, with various test cases.

  • Example: Running your app to see if it's working

Automated testing is writing code that tests your code for you.

  • Example: Writing code that tests the correctness of your app for various user inputs

Why Learn Automated Testing?

  1. Ensures that your next change won't break anything that was previously working
  • These are called regression tests
  1. Other developers can contribute to your project without fear of breaking it
  2. Improves accuracy of your code - easier to test many edge cases
  • What is an edge case?

Forms of Testing

How can I test my code?

We'll go over a couple of the most foundational tests you can run on your projects:

  1. Unit Testing - tests a single function
  2. Route Testing - tests what is served by a single route

Unit Tests

What are Unit Tests?

Unit tests test the output or return value of a single function.

They are very resilient and will rarely break as you make changes to your code, but they provide very narrow test coverage to your application as a whole so you have to write a lot of them.

Python has a built in unit test library called unittest that we'll use for running our unit tests going forward.

Example

Here's an example of a unit test that checks the output of a greet_by_name function. Check out the comments for details. Let's call this file test_greeting.py:

import unittest

def greet_by_name(name):
    """Greet user by name."""
    greeting = "Hello, " + name + "!"
    return greeting

class StringFunctionTests(unittest.TestCase):
    def test_greeting(self):
        """Test the greeting function."""
        self.assertEqual(greet_by_name('Dani'), 'Hello, Dani!')

if __name__ == '__main__':
    unittest.main()

Assertions

What does assertEqual mean? This is an example of an assertion!

An Assertion is a true/false statement that defines a test. In the above example, we're testing to make sure the greet_by_name('Dani') function returns Hello, Dani! as an answer.

Read more about assertions here.

Run the Test

If you were to run this function, you'd see the following output:

➜  ~ python3 string_tests.py
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

Great! Our test passed!

Question

What would happen if we change:

self.assertEqual(greet_by_name('Dani'), 'Hello, Dani!')

To the following:

self.assertEqual(greet_by_name('Dani'), 'Hello, Meredith!')

Fail!

Our two parameters to assertEqual no longer match, so the test would fail!

➜  ~ python3 test_greeting.py
F
======================================================================
FAIL: test_default_greeting_set (__main__.GreetByNameTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_greeting.py", line 10, in test_default_greeting_set
    self.assertEqual(greet_by_name('Dani'), 'Hello, Meredith!')
AssertionError: 'Hello, Dani!' != 'Hello, Meredith!'
- Hello, Dani!
+ Hello, Meredith!


----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (failures=1)

Activity: Write some Tests

Clone the repository here and write tests for the other functions.

Break [10 minutes]

Route Tests

What is Route Testing?

Route Tests test a single route. They are typically more broad than unit tests, but will not break when we change something minor like the styling.

Route Testing Example

Here's an example of testing a route:

from app import app
import unittest 

class AppTests(unittest.TestCase): 
    
    def setUp(self):
        self.app = app.test_client()
        self.app.testing = True 

    def test_homepage(self):
        """Verify that homepage renders correctly."""
        result = self.app.get('/')
        self.assertEqual(result.status_code, 200)
        page_content = result.get_data(as_text=True)
        self.assertIn('Hello world', page_content)

What if I want to test with specific form input?

We can simulate a user entering "Cat" into the "Favorite animal?" input box by changing the query string.

def test_fortune_cat(self):
    """Verify that homepage renders correctly."""
    result = self.app.get('/fortune_results?animal=cat')
    self.assertEqual(result.status_code, 200)

    page_content = result.get_data(as_text=True)
    self.assertIn('Your day will be paw-some', page_content)

Activity: Test Fortune Teller

Write at least four route tests for your Fortune Teller project (one for each possible fortune).

Vibe Check

Go to https://make.sc/bew1.1-vibe-check and fill out the form.

Homework

Homework 3 (Weather App) is due on Thursday, at midnight.

Resources