Basic assert statement in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assert that the sum of 2 and 3 equals 5.

PyTest

def test_sum():
    result = 2 + 3
    assert result [1] 5

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

A=

B<

C!=

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' instead of '==' in the assert statement.

Using '!=' which checks for inequality.

The assert statement checks if the expression is true. Here, result == 5 verifies the sum is correct.

2fill in blank

medium

Complete the code to assert that the length of the list is 4.

PyTest

def test_list_length():
    items = [1, 2, 3, 4]
    assert len(items) [1] 4

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

A>

B<

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' or '>' which check less or greater than, not equality.

Using '!=' which checks for inequality.

The assert checks if the length of items is exactly 4 using ==.

3fill in blank

hard

Fix the error in the assert statement to correctly check if the variable is True.

PyTest

def test_is_active():
    is_active = True
    assert is_active [1] True

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

A==

Bis

C=

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' instead of '==' in assert.

Using 'is' which is for identity, not equality.

The correct way to compare values in an assert is with ==. Using = causes a syntax error.

4fill in blank

hard

Fill both blanks to assert that the variable score is greater than 50.

PyTest

def test_score():
    score = 75
    assert score [1] [2]

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

A>

B50

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '>' for greater than check.

Using '<' which checks less than.

The assert checks if score is greater than 50 using > and the number 50.

5fill in blank

hard

Fill all three blanks to assert that the length of names is less than 5 and the first name is 'Alice'.

PyTest

def test_names():
    names = ['Alice', 'Bob', 'Charlie']
    assert len(names) [1] [2] and names[0] [3] 'Alice'

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

A<

B5

C==

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' for length check.

Using '=' instead of '==' for string comparison.

The assert checks two things: length of names is less than 5 (< and 5), and the first name equals 'Alice' (==).

Practice

1. What does the assert statement do in a pytest test?

easy

A. Skips the test without running it

B. Runs the test multiple times automatically

C. Prints a message to the console

D. Checks if a condition is true and stops the test if false

Solution

1. Step 1: Understand the purpose of assert

   The assert statement checks if a condition is true during a test.

2. Step 2: Know the effect of assert failing

   If the condition is false, the test stops and reports failure.

3. Final Answer:

   Checks if a condition is true and stops the test if false -> Option D

4. Quick Check:

   Assert = condition check [OK]

Hint: Assert stops test on false condition [OK]

Common Mistakes:

• Thinking assert runs tests multiple times
• Confusing assert with print statements
• Believing assert skips tests

2. Which of the following is the correct syntax for an assert statement in pytest?

easy

A. assert(x == 5; "x should be 5")

B. assert x == 5, "x should be 5"

C. assert x = 5, "x should be 5"

D. assert x == 5 then "x should be 5"

Solution

1. Step 1: Review correct assert syntax

   In Python, assert is followed by a condition, optionally a comma and a message string.

2. Step 2: Identify syntax errors in options

   assert x == 5, "x should be 5" uses correct syntax: assert condition, message. Others have wrong punctuation or assignment.

3. Final Answer:

   assert x == 5, "x should be 5" -> Option B

4. Quick Check:

   assert condition, message [OK]

Hint: Use comma after condition for message [OK]

Common Mistakes:

• Using assignment (=) instead of comparison (==)
• Adding parentheses incorrectly
• Using wrong keywords like 'then'

3. What will be the result of this pytest assertion?

def test_value():
    x = 10
    assert x < 5, "x is not less than 5"

medium

A. Test passes silently

B. Test is skipped

C. Test fails with message 'x is not less than 5'

D. SyntaxError occurs

Solution

1. Step 1: Evaluate the condition in assert

   The condition is x < 5, but x is 10, so 10 < 5 is false.

2. Step 2: Understand assert failure behavior

   Since condition is false, the test fails and shows the message after the comma.

3. Final Answer:

   Test fails with message 'x is not less than 5' -> Option C

4. Quick Check:

   False condition triggers failure [OK]

Hint: False assert condition fails test with message [OK]

Common Mistakes:

• Assuming test passes when condition is false
• Expecting syntax error for valid assert
• Thinking test skips on failure

4. Identify the error in this pytest assertion:

def test_sum():
    total = 3 + 4
    assert total = 7, "Sum should be 7"

medium

A. Using assignment (=) instead of comparison (==) in assert

B. Missing parentheses around assert condition

C. Incorrect indentation of assert statement

D. Wrong message format after assert

Solution

1. Step 1: Check assert condition syntax

   The assert condition must use comparison (==), not assignment (=).

2. Step 2: Identify the error in the code

   Here, 'assert total = 7' uses assignment, which is invalid syntax.

3. Final Answer:

   Using assignment (=) instead of comparison (==) in assert -> Option A

4. Quick Check:

   Use '==' for comparison in assert [OK]

Hint: Use '==' not '=' in assert condition [OK]

Common Mistakes:

• Confusing assignment with comparison
• Adding unnecessary parentheses
• Misplacing the error in indentation

5. You want to check if a list items contains exactly 3 elements using pytest assert. Which is the best assert statement?

hard

A. assert len(items) == 3, "List does not have 3 elements"

B. assert items == 3, "List length check failed"

C. assert items.length == 3, "Wrong length"

D. assert len(items) = 3, "Length must be 3"

Solution

1. Step 1: Understand how to get list length in Python

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

2. Step 2: Check correct assert syntax for length comparison

   Compare len(items) with 3 using '==', and provide a clear message after a comma.

3. Final Answer:

   assert len(items) == 3, "List does not have 3 elements" -> Option A

4. Quick Check:

   len(list) == number [OK]

Hint: Use len() and '==' to check list size [OK]

Common Mistakes:

• Comparing list directly to number
• Using JavaScript style .length property
• Using assignment '=' instead of '=='