Given-When-Then pattern in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to mark the 'Given' step in a pytest test function.

PyTest

def test_addition():
    # [1]: Setup numbers
    a = 2
    b = 3
    result = a + b
    assert result == 5

Drag options to blanks, or click blank then click option'

AAssert

BWhen

CThen

DGiven

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing 'Given' with 'When' or 'Then' steps.

The 'Given' step sets up the initial context or data for the test.

2fill in blank

medium

Complete the code to mark the 'When' step where the action happens.

PyTest

def test_subtraction():
    a = 5
    b = 3
    # [1]: Perform subtraction
    result = a - b
    assert result == 2

Drag options to blanks, or click blank then click option'

AWhen

BSetup

CThen

DGiven

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Given' or 'Then' instead of 'When' for the action step.

The 'When' step describes the action or event being tested.

3fill in blank

hard

Fix the error in the 'Then' step comment describing the expected outcome.

PyTest

def test_multiplication():
    a = 4
    b = 3
    result = a * b
    # [1]: Check if result equals 12
    assert result == 12

Drag options to blanks, or click blank then click option'

AGiven

BWhen

CThen

DCheck

Attempts:

3 left

💡 Hint

Common Mistakes

Labeling the 'Then' step as 'When' or 'Given'.

The 'Then' step verifies the expected result or outcome of the test.

4fill in blank

hard

Fill both blanks to complete the Given-When-Then comments in the test.

PyTest

def test_division():
    # [1]: Setup numbers
    numerator = 10
    denominator = 2
    # [2]: Perform division
    result = numerator / denominator
    assert result == 5

Drag options to blanks, or click blank then click option'

AGiven

BWhen

CThen

DSetup

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping 'Given' and 'When' labels.

'Given' sets up the data, 'When' performs the action.

5fill in blank

hard

Fill all three blanks to complete the Given-When-Then pattern in the test function.

PyTest

def test_string_upper():
    # [1]: Setup input string
    input_str = "hello"
    # [2]: Convert string to uppercase
    result = input_str.upper()
    # [3]: Verify the result is uppercase
    assert result == "HELLO"

Drag options to blanks, or click blank then click option'

AGiven

BWhen

CThen

DAssert

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of Given, When, Then.

'Given' sets up data, 'When' performs action, 'Then' checks result.

Practice

1. What is the main purpose of the Given-When-Then pattern in pytest tests?

easy

A. To write tests only for user interface elements

B. To organize tests into setup, action, and verification steps

C. To speed up test execution by skipping setup

D. To avoid using assertions in tests

Solution

1. Step 1: Understand the pattern roles

   Given-When-Then divides a test into three parts: Given (setup), When (action), Then (check).

2. Step 2: Match purpose with options

   Only To organize tests into setup, action, and verification steps correctly describes this organization purpose.

3. Final Answer:

   To organize tests into setup, action, and verification steps -> Option B

4. Quick Check:

   Given-When-Then = organize test steps [OK]

Hint: Remember: Given=setup, When=action, Then=check [OK]

Common Mistakes:

• Thinking it only applies to UI tests
• Believing it skips setup steps
• Assuming no assertions are used

2. Which of the following is the correct way to write a Given-When-Then style pytest test function?

easy

A. def test_example():
# Given
x = 5
# When
y = x + 3
# Then
assert y == 8

B. def test_example():
x = 5
y = x + 3
assert y == 8
# Given-When-Then comments missing

C. def test_example():
assert 5 + 3 == 8
# Given-When-Then not used

D. def test_example():
# When
x = 5
# Given
y = x + 3
# Then
assert y == 8

Solution

1. Step 1: Check comment order and code logic

   def test_example(): # Given x = 5 # When y = x + 3 # Then assert y == 8 correctly uses Given-When-Then comments in order with proper setup, action, and assertion.

2. Step 2: Identify incorrect patterns

   The other options either lack Given-When-Then comments or have them in the wrong order (e.g., When before Given).

3. Final Answer:

   def test_example():\n # Given\n x = 5\n # When\n y = x + 3\n # Then\n assert y == 8 -> Option A

4. Quick Check:

   Correct comment order = def test_example(): # Given x = 5 # When y = x + 3 # Then assert y == 8 [OK]

Hint: Follow comment order: Given, When, Then [OK]

Common Mistakes:

• Mixing the order of Given and When comments
• Skipping comments entirely
• Placing assertions outside Then step

3. Given the following pytest test using Given-When-Then pattern, what will be the test result?

def test_sum():
    # Given
    numbers = [1, 2, 3]
    # When
    total = sum(numbers)
    # Then
    assert total == 6

medium

A. Test will fail because assertion is wrong

B. Test will fail because sum is calculated incorrectly

C. Test will error due to missing import

D. Test will pass because sum of [1, 2, 3] is 6

Solution

1. Step 1: Calculate sum of list

   The sum of [1, 2, 3] is 1+2+3 = 6.

2. Step 2: Check assertion correctness

   The assertion checks total == 6, which is true, so test passes.

3. Final Answer:

   Test will pass because sum of [1, 2, 3] is 6 -> Option D

4. Quick Check:

   sum([1,2,3]) = 6 [OK]

Hint: Calculate sum and compare with assertion value [OK]

Common Mistakes:

• Assuming sum returns a list instead of number
• Thinking assertion expects a different value
• Confusing test error with failure

4. Identify the error in this Given-When-Then pytest test:

def test_multiply():
    # Given
    x = 4
    y = 5
    # When
    result = x * y
    # Then
    assert result = 20

medium

A. Syntax error in assertion statement

B. Wrong variable names used

C. Missing setup in Given step

D. No assertion in Then step

Solution

1. Step 1: Check assertion syntax

   The assertion uses single '=' which is assignment, not comparison. It should be '==' for comparison.

2. Step 2: Confirm other parts are correct

   Variables and steps are correct; only assertion syntax is wrong.

3. Final Answer:

   Syntax error in assertion statement -> Option A

4. Quick Check:

   Use '==' in assert, not '=' [OK]

Hint: Use '==' for assert comparisons, not '=' [OK]

Common Mistakes:

• Using '=' instead of '==' in assert
• Confusing assignment with comparison
• Ignoring syntax errors in assertions

5. You want to test a function that filters out falsy values (like 0, '', None) from a list using Given-When-Then pattern in pytest. Which test code correctly applies this pattern and checks the result?

hard

A. def test_filter_falsy():
# Given
data = [0, 1, '', 'hello', None, True]
# Then
assert filtered == [1, 'hello', True]
# When
filtered = [x for x in data if x]

B. def test_filter_falsy():
data = [0, 1, '', 'hello', None, True]
filtered = [x for x in data if x]
assert filtered == [1, 'hello', True]

C. def test_filter_falsy():
# Given
data = [0, 1, '', 'hello', None, True]
# When
filtered = [x for x in data if x]
# Then
assert filtered == [1, 'hello', True]

D. def test_filter_falsy():
# Given
data = [0, 1, '', 'hello', None, True]
# When
filtered = filter(lambda x: x, data)
# Then
assert list(filtered) == [0, 1, '', 'hello', None, True]

Solution

1. Step 1: Verify Given-When-Then structure

   def test_filter_falsy(): # Given data = [0, 1, '', 'hello', None, True] # When filtered = [x for x in data if x] # Then assert filtered == [1, 'hello', True] correctly uses Given for data setup, When for filtering action, Then for assertion check.

2. Step 2: Check correctness of filtering and assertion

   Filtering removes falsy values; expected list matches filtered result. Other options miss comments or have wrong assertion.

3. Final Answer:

   def test_filter_falsy():\n # Given\n data = [0, 1, '', 'hello', None, True]\n # When\n filtered = [x for x in data if x]\n # Then\n assert filtered == [1, 'hello', True] -> Option C

4. Quick Check:

   Given-When-Then + correct filter = def test_filter_falsy(): # Given data = [0, 1, '', 'hello', None, True] # When filtered = [x for x in data if x] # Then assert filtered == [1, 'hello', True] [OK]

Hint: Keep steps clear: setup, action, then check [OK]

Common Mistakes:

• Skipping Given-When-Then comments
• Asserting wrong filtered list
• Using filter object without converting to list