Arrange-Act-Assert pattern in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to arrange the test data correctly.

PyTest

def test_sum():
    numbers = [1]
    result = sum(numbers)
    assert result == 6

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

A(1, 2, 3)

B[1, 2, 3]

C{1, 2, 3}

D1, 2, 3

Attempts:

3 left

💡 Hint

Common Mistakes

Using a tuple or set instead of a list.

Not using any container for numbers.

The test data should be a list to use with sum(). So [1, 2, 3] is correct.

2fill in blank

medium

Complete the code to act by calling the function under test.

PyTest

def test_uppercase():
    text = "hello"
    result = text.[1]()
    assert result == "HELLO"

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

Aupper

Blower

Ccapitalize

Dtitle

Attempts:

3 left

💡 Hint

Common Mistakes

Using lower() which converts to lowercase.

Using capitalize() which only changes the first letter.

The upper() method converts text to uppercase, matching the assertion.

3fill in blank

hard

Fix the error in the assertion to correctly check the result.

PyTest

def test_length():
    word = "test"
    length = len(word)
    assert length [1] 5

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

A==

B>

C<

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using == 5 which fails because length is 4.

Using > 5 which is false.

The length of "test" is 4, which is less than 5, so < is correct.

4fill in blank

hard

Fill both blanks to create a test that asserts a list contains a value.

PyTest

def test_contains():
    items = [1, 2, 3]
    value = 2
    assert value [1] items[2]

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

Ain

Bnot in

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using == which compares value to the whole list.

Using not in which would fail the test.

The correct syntax to check if a value is in a list is value in items. The second blank is empty because no extra operator is needed.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that filters items by value.

PyTest

def test_filter_dict():
    data = {'a': 1, 'b': 3, 'c': 2}
    filtered = {k: v for k, v in data.items() if v [1] [2]
    assert filtered == [3]

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

A>

B1

C{'b': 3, 'c': 2}

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > which changes the filter.

Using wrong expected dictionary in the assertion.

The comprehension filters values greater than 1, so v > 1. The expected filtered dictionary is {'b': 3, 'c': 2}.

Practice

1. What is the main purpose of the Arrange-Act-Assert pattern in pytest?

easy

A. To speed up test execution time

B. To organize tests into clear steps for better readability

C. To automatically generate test data

D. To replace the need for assertions in tests

Solution

1. Step 1: Understand the pattern's goal

   The Arrange-Act-Assert pattern structures tests into three parts: setup, action, and verification.

2. Step 2: Identify the main benefit

   This structure makes tests easier to read and maintain by clearly separating steps.

3. Final Answer:

   To organize tests into clear steps for better readability -> Option B

4. Quick Check:

   Arrange-Act-Assert = Organize tests clearly [OK]

Hint: Remember: Arrange sets up, Act performs, Assert checks [OK]

Common Mistakes:

• Thinking it speeds up test execution
• Confusing it with test data generation
• Believing it removes the need for assertions

2. Which of the following is the correct order of steps in the Arrange-Act-Assert pattern?

easy

A. Act, Arrange, Assert

B. Assert, Arrange, Act

C. Arrange, Act, Assert

D. Act, Assert, Arrange

Solution

1. Step 1: Recall the pattern sequence

   The pattern always starts with Arrange (setup), then Act (perform action), and finally Assert (check results).

2. Step 2: Match the correct order

   Only Arrange, Act, Assert follows this exact sequence.

3. Final Answer:

   Arrange, Act, Assert -> Option C

4. Quick Check:

   Order is Arrange -> Act -> Assert [OK]

Hint: Think: Prepare, Do, Check in that order [OK]

Common Mistakes:

• Mixing up the order of steps
• Starting with Assert before Act
• Confusing Act and Arrange steps

3. Given the following pytest test code, what will be the test result?

def test_sum():
    # Arrange
    numbers = [1, 2, 3]
    expected = 6

    # Act
    result = sum(numbers)

    # Assert
    assert result == expected

medium

A. Test will pass because sum(numbers) equals expected

B. Test will fail because sum is not defined

C. Test will fail because expected is incorrect

D. Test will error due to syntax mistake

Solution

1. Step 1: Analyze the Arrange step

   List numbers is [1, 2, 3] and expected sum is 6, which is correct.

2. Step 2: Check the Act and Assert steps

   sum(numbers) calculates 6, matching expected. The assertion will pass.

3. Final Answer:

   Test will pass because sum(numbers) equals expected -> Option A

4. Quick Check:

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

Hint: Check if actual equals expected in Assert step [OK]

Common Mistakes:

• Assuming sum is undefined
• Thinking expected value is wrong
• Looking for syntax errors where none exist

4. Identify the error in this pytest test using Arrange-Act-Assert pattern:

def test_uppercase():
    # Arrange
    text = "hello"

    # Act
    result = text.upper

    # Assert
    assert result == "HELLO"

medium

A. Missing parentheses in Act step calling upper()

B. Incorrect expected value in Assert step

C. Variable text is not defined in Arrange step

D. Assert statement syntax is invalid

Solution

1. Step 1: Review the Act step

   text.upper is a method reference, missing parentheses to call it.

2. Step 2: Understand the impact on Assert

   Without calling upper(), result is a method, not a string, so assertion fails.

3. Final Answer:

   Missing parentheses in Act step calling upper() -> Option A

4. Quick Check:

   Call methods with () to get results [OK]

Hint: Remember to call methods with parentheses () [OK]

Common Mistakes:

• Thinking expected value is wrong
• Assuming variable is undefined
• Believing assert syntax is incorrect

5. You want to test a function divide(a, b) that returns the division of two numbers. Using Arrange-Act-Assert, which test correctly checks that dividing by zero raises a ZeroDivisionError?

hard

A. def test_divide_zero():
# Arrange
a, b = 10, 0
# Act
result = divide(a, b)
# Assert
assert result == 0

B. def test_divide_zero():
# Arrange
a, b = 10, 0
# Act
result = divide(a, b)
# Assert
assert result is None

C. def test_divide_zero():
# Arrange
a, b = 10, 0
# Act
divide(a, b)
# Assert
assert True

D. def test_divide_zero():
# Arrange
a, b = 10, 0
# Act & Assert
with pytest.raises(ZeroDivisionError):
divide(a, b)

Solution

1. Step 1: Understand the test goal

   The test must verify that dividing by zero raises a ZeroDivisionError exception.

2. Step 2: Identify correct pytest usage

   Using with pytest.raises(ZeroDivisionError): correctly checks for the exception during Act step.

3. Final Answer:

   Using pytest.raises to check for ZeroDivisionError -> Option D

4. Quick Check:

   Use pytest.raises to test exceptions [OK]

Hint: Use pytest.raises to assert exceptions in tests [OK]

Common Mistakes:

• Ignoring exception and asserting wrong result
• Not using pytest.raises for exception testing
• Asserting True without checking error