Writing tests

Running tests

> python tests/module_name.py

Write tests as you go

For example, let's say you are writing a function to format a string to read "You have ## fish", where ## is an input to the function. You might start by writing a function shell something like this, in aopy/tutorial_functions.py:

def practice_func_leo(number_of_fish):
    '''
    This function formats a string to say how many fish you have

    Inputs:
        number_of_fish (int): How many fish you have
        
    Outputs:
        str: a string describing how many fish you have
    '''
    pass

Next, you should write a test function in tests/test_tutorial_functions.py. Name your test function test_ followed by the function name:

def test_leo_practice(self):
    output = aopy.tutorial_functions.practice_func_leo(3)
        self.assertEqual(output, 'You have 3 fish')

Since I know what the output should be, without programming anything, I can set up the test to check that the function works.

Now I can implement the function:

def practice_func_leo(number_of_fish):
    '''
    '''
    return 'You have 3 fish'

... and it passes the tests! But wait! This function completely ignores the number_of_fish input and always says you have 3 fish. We need to add a slightly better test. For example:

def test_leo_practice(self):
    output = aopy.tutorial_functions.practice_func_leo(3)
    self.assertEqual(output, 'You have 3 fish')
    
    output = aopy.tutorial_functions.practice_func_leo(0)
    self.assertEqual(output, 'You have 0 fish')

And update the code to pass this test:

def practice_func_leo(number_of_fish):
    '''
    '''
    return 'You have {} fish'.format(number_of_fish)

Of course, this is a contrived example and you wouldn't actually need to write comprehensive tests on a one-line function.