Test classes in PyTest - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a test class in pytest?

A test class in pytest is a Python class that groups related test methods together. It helps organize tests logically without needing to inherit from any special base class.

beginner

How do you name test methods inside a pytest test class?

Test methods inside a pytest test class should start with the prefix <code>test_</code>. This naming lets pytest automatically find and run them.

intermediate

Can pytest test classes have setup and teardown methods? How?

Yes. You can define setup_method(self, method) and teardown_method(self, method) inside the test class. These run before and after each test method respectively.

intermediate

Why use test classes instead of just functions in pytest?

Test classes help group related tests, share setup code, and improve readability. They make tests easier to maintain, especially when many tests share common setup.

beginner

Show a simple pytest test class with two test methods and a setup method.

class TestMathOperations:
    def setup_method(self, method):
        self.value = 10

    def test_add(self):
        assert self.value + 5 == 15

    def test_subtract(self):
        assert self.value - 3 == 7

What prefix should test methods inside a pytest test class have?

A check_

B test_

C verify_

D run_

Pytest automatically discovers test methods that start with test_.

Which method runs before each test method in a pytest test class?

A setup_function

B setup_class

C setup_module

D setup_method

setup_method runs before each test method in the class.

Do pytest test classes need to inherit from a special base class?

A Yes, from unittest.TestCase

B Yes, from object

C No, inheritance is not required

D Yes, from pytest.BaseTest

Pytest test classes do not require inheritance from any base class.

What is a main benefit of using test classes in pytest?

A They group related tests and share setup

B They run tests faster

C They automatically generate test data

D They replace the need for fixtures

Test classes help organize related tests and share setup code.

Which of these is a valid pytest test class name?

A TestCalculator

B calculatorTests

C testclass

D MyTests

Test classes should start with Test to be easily recognized.

Explain how to organize multiple related tests using pytest test classes.

Think about grouping and shared setup.

Describe the role of setup_method and teardown_method in pytest test classes.

Consider what happens before and after each test.

Practice

1. What is the main purpose of using test classes in pytest?

easy

A. To avoid writing assertions

B. To group related tests for better organization

C. To make tests run faster

D. To skip tests automatically

Solution

1. Step 1: Understand test grouping

   Test classes help organize related test functions together in one place.

2. Step 2: Recognize benefits

   This grouping improves readability and allows shared setup for tests.

3. Final Answer:

   To group related tests for better organization -> Option B

4. Quick Check:

   Test classes group tests = C [OK]

Hint: Test classes group related tests logically [OK]

Common Mistakes:

• Thinking test classes speed up tests
• Believing test classes skip tests
• Assuming test classes remove need for assertions

2. Which of the following is the correct way to name a pytest test class?

easy

A. class testExample:

B. class ExampleTest:

C. class TestExample:

D. class exampleTest:

Solution

1. Step 1: Recall pytest naming rules

   Pytest requires test classes to start with 'Test' exactly.

2. Step 2: Check options

   Only 'TestExample' starts with 'Test' correctly and follows naming conventions.

3. Final Answer:

   class TestExample: -> Option C

4. Quick Check:

   Class name starts with 'Test' = D [OK]

Hint: Test classes must start with 'Test' exactly [OK]

Common Mistakes:

• Starting class name with lowercase 'test'
• Placing 'Test' at the end of class name
• Using mixed case that doesn't start with 'Test'

3. Given the code below, what will pytest report when running these tests?

class TestMath:
    def test_add(self):
        assert 1 + 1 == 2

    def test_subtract(self):
        assert 5 - 3 == 1

medium

A. 1 test passed, 1 test failed

B. 2 tests passed

C. 2 tests failed

D. Syntax error, tests won't run

Solution

1. Step 1: Check each assertion

   test_add asserts 1+1==2 which is True; test_subtract asserts 5-3==1 which is False.

2. Step 2: Determine test results

   One test passes (test_add), one test fails (test_subtract).

3. Final Answer:

   1 test passed, 1 test failed -> Option A

4. Quick Check:

   Assertions true/false = 1 pass, 1 fail [OK]

Hint: Check each assertion result carefully [OK]

Common Mistakes:

• Assuming both tests pass without checking assertions
• Ignoring that 5 - 3 != 1
• Thinking syntax error due to indentation

4. Identify the error in the following pytest test class:

class TestCalc:
    def test_multiply(self):
        assert 2 * 3 == 6
    
    def multiply_test(self):
        assert 4 * 5 == 20

medium

A. Method 'multiply_test' will not be recognized as a test

B. Class name must not start with 'Test'

C. Missing assert statement in 'test_multiply'

D. Indentation error in method definitions

Solution

1. Step 1: Check method naming rules

   Pytest requires test methods to start with 'test_'. 'multiply_test' does not.

2. Step 2: Understand consequences

   Method 'multiply_test' will be ignored by pytest and not run as a test.

3. Final Answer:

   Method 'multiply_test' will not be recognized as a test -> Option A

4. Quick Check:

   Test methods start with 'test_' = A [OK]

Hint: Test methods must start with 'test_' [OK]

Common Mistakes:

• Thinking class name can't start with 'Test'
• Missing assert in test method
• Assuming indentation error without evidence

5. How can you share setup code for all tests inside a pytest test class?

hard

A. Define a method named 'setup_method' inside the class

B. Use a global variable outside the class

C. Write setup code inside each test method separately

D. Define a method named 'setup_class' inside the class

Solution

1. Step 1: Understand pytest setup methods

   Pytest supports 'setup_class' to run setup once for all tests in a class.

2. Step 2: Compare options

   'setup_method' runs before each test method, not once for all; global variables and repeated code are not best practice.

3. Final Answer:

   Define a method named 'setup_class' inside the class -> Option D

4. Quick Check:

   Class-wide setup uses 'setup_class' = B [OK]

Hint: Use 'setup_class' for one-time class setup [OK]

Common Mistakes:

• Confusing 'setup_method' with class-wide setup
• Using global variables instead of setup methods
• Repeating setup code in every test method