First PyTest test - Test Execution Trace

Test Overview

This test checks if the addition of two numbers works correctly using PyTest. It verifies that 2 + 3 equals 5.

Test Code - PyTest

PyTest

import pytest

def test_addition():
    result = 2 + 3
    assert result == 5

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts	PyTest test runner is ready to execute tests	—	PASS
2	Calls test_addition function	Inside test function, variables initialized	—	PASS
3	Calculates result = 2 + 3	result variable holds value 5	—	PASS
4	Checks assertion assert result == 5	Comparing result (5) with expected value (5)	Assert that result equals 5	PASS
5	Test ends successfully	Test runner marks test as passed	—	PASS

Failure Scenario

Failing Condition: If the assertion result == 5 fails (for example, result is not 5)

Execution Trace Quiz - 3 Questions

What does the assertion in the test check?

A If result is greater than 5

B If 2 + 3 equals 6

C If 2 + 3 equals 5

D If result is less than 5

Key Result

Always write simple assertions that clearly check expected results. This helps catch errors early and makes tests easy to understand.

Practice

1. What does PyTest look for to identify a test function?

easy

A. Functions decorated with @pytest.test

B. Functions ending with _test

C. Functions starting with test_

D. Functions containing assert keyword

Solution

1. Step 1: Understand PyTest naming convention

   PyTest automatically finds functions whose names start with test_.

2. Step 2: Compare options with PyTest rules

   Only functions starting with test_ are recognized as tests by default.

3. Final Answer:

   Functions starting with test_ -> Option C

4. Quick Check:

   PyTest test function = starts with test_ [OK]

Hint: Look for functions starting with test_ to find tests [OK]

Common Mistakes:

• Thinking functions ending with _test are tests
• Believing assert keyword alone marks a test
• Assuming decorators are needed for basic tests

2. Which of the following is the correct syntax for a simple PyTest test function?

easy

A. def add_test():\n assert 1 + 1 == 2

B. def test_add():\n assert 1 + 1 == 2

C. def test_add():\n assert 1 + 1 == 3

D. def testAdd():\n assert 1 + 1 == 2

Solution

1. Step 1: Check function name format

   PyTest requires test functions to start with test_, so test_add is correct.

2. Step 2: Verify assertion correctness

   The assertion 1 + 1 == 2 is true, so the test will pass.

3. Final Answer:

   def test_add():\n assert 1 + 1 == 2 -> Option B

4. Quick Check:

   Correct test name and true assert = def test_add():\n assert 1 + 1 == 2 [OK]

Hint: Use def test_...() with assert for valid PyTest tests [OK]

Common Mistakes:

• Naming function without test_ prefix
• Using incorrect assertion values
• Using camelCase instead of snake_case for test names

3. What will be the result when running this PyTest test?

def test_example():
    x = 5
    y = 2
    assert x - y == 3

medium

A. Test passes successfully

B. SyntaxError occurs

C. Test fails with AssertionError

D. Test is skipped automatically

Solution

1. Step 1: Evaluate the assertion expression

   Calculate x - y which is 5 - 2 = 3.

2. Step 2: Compare with asserted value

   The assertion checks if 3 == 3, which is true, so no error is raised.

3. Final Answer:

   Test passes successfully -> Option A

4. Quick Check:

   5 - 2 equals 3 means assert passes [OK]

Hint: Calculate assert expression; true means test passes [OK]

Common Mistakes:

• Assuming test fails without checking assertion
• Confusing syntax errors with assertion failures
• Thinking tests skip without skip decorators

4. Identify the error in this PyTest test function:

def test_sum():
    total = 2 + 2
    assert total = 4

medium

A. Using single equals (=) instead of double equals (==) in assert

B. Function name does not start with test_

C. Missing return statement in test function

D. Indentation error in function body

Solution

1. Step 1: Check the assert statement syntax

   The assert uses = which is assignment, not comparison. It should be ==.

2. Step 2: Confirm function name and indentation

   The function name starts with test_ and indentation is correct, so no error there.

3. Final Answer:

   Using single equals (=) instead of double equals (==) in assert -> Option A

4. Quick Check:

   Assert needs ==, not = [OK]

Hint: Use == in assert, not = for comparison [OK]

Common Mistakes:

• Using = instead of == in assert
• Thinking return is needed in test functions
• Confusing indentation errors with syntax errors

5. You want to test a function multiply(a, b) that returns the product of two numbers. Which PyTest test function correctly tests that multiply(3, 4) returns 12?

hard

A. def test_multiply():\n assert multiply(3, 4) == 7

B. def test_multiply():\n assert multiply(3, 4) = 12

C. def multiply_test():\n assert multiply(3, 4) == 12

D. def test_multiply():\n assert multiply(3, 4) == 12

Solution

1. Step 1: Verify test function name

   The function name must start with test_, so test_multiply is correct.

2. Step 2: Check assertion correctness

   The assertion must compare with == and the expected result is 12, so assert multiply(3, 4) == 12 is correct.

3. Final Answer:

   def test_multiply():\n assert multiply(3, 4) == 12 -> Option D

4. Quick Check:

   Correct name and assert with == 12 = def test_multiply():\n assert multiply(3, 4) == 12 [OK]

Hint: Test functions start with test_ and assert expected == actual [OK]

Common Mistakes:

• Wrong expected value in assert
• Wrong function name prefix
• Using = instead of == in assert