First PyTest test - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this simple PyTest test?

Consider this PyTest test function. What will be the test result when you run it?

PyTest

def test_sum():
    assert 2 + 3 == 5

A Test fails with AssertionError

B Test passes successfully

C SyntaxError occurs due to missing colon

D RuntimeError due to undefined variable

💡 Hint

Check if the assertion condition is true or false.

The assertion 2 + 3 == 5 is true, so the test passes.

❓ assertion

intermediate

Which assertion will correctly check if a list contains exactly 3 items?

You want to write a PyTest assertion to verify that the list items = [1, 2, 3] has exactly 3 elements. Which option is correct?

A assert len(items) == 3

B assert items.count == 3

C assert items.length() == 3

D assert items.size == 3

💡 Hint

Use the built-in function to get the number of elements in a list.

The len() function returns the number of items in a list. The other options are invalid syntax or attributes.

🔧 Debug

advanced

Why does this PyTest test fail?

Look at this test code and find why it fails when run with PyTest.

PyTest

def test_divide():
    result = 10 / 0
    assert result == 0

A SyntaxError due to missing colon

B AssertionError because result is not zero

C ZeroDivisionError occurs before assertion

D Test passes because 10 divided by 0 is 0

💡 Hint

What happens when you divide by zero in Python?

Dividing by zero raises a ZeroDivisionError before the assertion runs, causing the test to error out.

❓ framework

advanced

Which PyTest feature allows running setup code before each test function?

You want to run some code before every test function in a file. Which PyTest feature should you use?

A Use a main() function to call setup manually

B Use a class with __init__ method for setup

C Use a global variable initialized outside tests

D Use a fixture with scope='function' and the @pytest.fixture decorator

💡 Hint

PyTest fixtures are designed for setup and teardown.

Fixtures with function scope run setup code before each test function automatically.

🧠 Conceptual

expert

What is the main advantage of using PyTest over basic assert statements in scripts?

Why do testers prefer PyTest framework instead of just writing assert statements in Python scripts?

A PyTest provides detailed test reports, fixtures, and easy test discovery

B PyTest runs code faster than plain Python scripts

C PyTest automatically fixes bugs in the code

D PyTest requires no installation and works out of the box

💡 Hint

Think about what features a testing framework adds beyond simple asserts.

PyTest offers features like detailed reports, setup/teardown fixtures, and automatic test discovery, which plain asserts do not provide.

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