Testing

Installing Pytest

In Repl.it: On the right tab, click the Packages icon. Search for pytest and add it to the project.

At Home: In your terminal type $ pip install pytest

Creating a test file

Your test file should be a separate file from the code you wish to test. Always name your test files according to the following rules:

Start with test_
Include the name of what you are testing
End with .py

Some good examples:

test_vector.py
test_sleep_in.py
test_main.py

Writing tests

In the test file:

Import the function you want to test.
Create a test function starting with test_
Write Assertions to test the function you want to test.

Assertions

Assertions consist of two main parts.

Calling the function you want to test (with arguments)
Comparing the actual result to an expected result.

# a general assertion pattern
assert some_function() == "expected result"

# some specific examples
assert add(5, 7) == 12
assert add(1, 1) == 2

assert say_hello("Dave") == "Hello, Dave."
assert say_hello("Mr. Gallo") == "Hello, Mr. Gallo."

A complete test file

from main import add, say_hello


def test_add():
    assert add(5, 7) == 12
    assert add(1, 1) == 2


def test_say_hello():
    assert say_hello("Dave") == "Hello, Dave."
    assert say_hello("Mr. Gallo") == "Hello, Mr. Gallo."

Running Pytest

In the terminal, just type pytest. Alternatively, if you want to run a single, specific test file, you include the name of that file. For example pytest test_main.py.

Testing Object Attributes

# test_animal.py

from animal import Animal


def test_can_create_animal():
    a = Animal("Homo", "Sapiens")
    assert a.genus == "Homo"
    assert a.species == "Sapiens"
    assert a.happiness == 100

# animal.py

class Animal:
    def __init__(self, genus: str, species: str):
        self.genus = genus
        self.species = species
        self.happiness = 100

Testing Object Methods

# test_animal.py

def test_eat():
    dog = Animal("Canis", "Familiaris")
    dog.eat()
    assert dog.happiness == 150

    dog.eat()
    dog.eat()
    assert dog.happiness == 250

def test_sleep():
    dog = Animal("Canis", "Familiaris")
    dog.sleep(5)
    assert dog.happiness == 160

    # Shouldn't award points for sleeping 0 hours
    cat = Animal("Blah", "Whocares")
    cat.sleep(0)
    assert cat.happiness == 100

# animal.py

class Animal:
    def __init__(self, genus: str, species: str):
        self.genus = genus
        self.species = species
        self.happiness = 100

    def __str__(self) -> str:
        return f"{self.genus} {self.species}"

    def eat(self) -> None:
        self.happiness += 50

    def sleep(self, time: int) -> None:
        if time > 0:
            self.happiness += 2*time + 50