Parametrize with IDs in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to parametrize a test with two values.

PyTest

import pytest

@pytest.mark.parametrize('num', [1])
def test_is_positive(num):
    assert num > 0

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

A[1, 2]

B(1, 2)

C{1, 2}

D'1, 2'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a list or tuple.

Using a set which is unordered and not recommended here.

The @pytest.mark.parametrize decorator expects an iterable like a list or tuple. Using a list [1, 2] correctly passes the values.

2fill in blank

medium

Complete the code to parametrize a test with two arguments and IDs.

PyTest

import pytest

@pytest.mark.parametrize(
    'input,expected',
    [(2, 4), (3, 9)],
    ids=[1]
)
def test_square(input, expected):
    assert input ** 2 == expected

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

A['two', 'three']

B['2', '3']

C['square2', 'square3']

D['input2', 'input3']

Attempts:

3 left

💡 Hint

Common Mistakes

Using numbers instead of strings for IDs.

Using IDs list length different from test cases.

The ids parameter takes a list of strings to name each test case. Using ['two', 'three'] clearly identifies the test cases.

3fill in blank

hard

Fix the error in the parametrize decorator by completing the IDs argument correctly.

PyTest

import pytest

@pytest.mark.parametrize(
    'value',
    [10, 20, 30],
    ids=[1]
)
def test_greater_than_five(value):
    assert value > 5

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

A['10', '20']

B['10', '20', 30]

C['ten', 'twenty', 'thirty', 'forty']

D['10', '20', '30']

Attempts:

3 left

💡 Hint

Common Mistakes

Providing fewer or more IDs than test cases.

Mixing string and integer types in IDs.

The ids list must have the same number of elements as the test data. Here, three values require three ID strings.

4fill in blank

hard

Fill both blanks to parametrize a test with multiple arguments and custom IDs.

PyTest

import pytest

@pytest.mark.parametrize(
    [1],
    [(1, 'a'), (2, 'b')],
    ids=[2]
)
def test_multiple_args(num, char):
    assert isinstance(num, int) and isinstance(char, str)

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

A'num, char'

B'number, letter'

C['case1', 'case2']

D['first', 'second']

Attempts:

3 left

💡 Hint

Common Mistakes

Using a list instead of a string for argument names.

Mismatch between number of IDs and test cases.

The first blank is the string of argument names separated by commas. The second blank is a list of ID strings matching the test cases.

5fill in blank

hard

Fill all three blanks to parametrize a test with three arguments, test data, and custom IDs.

PyTest

import pytest

@pytest.mark.parametrize(
    [1],
    [2],
    ids=[3]
)
def test_three_args(x, y, z):
    assert x < y < z

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

A'x, y, z'

B[(1, 2, 3), (4, 5, 6)]

C['first', 'second']

D['a', 'b']

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect data types for arguments or test data.

Mismatch in length between test data and IDs.

The first blank is the string of argument names. The second blank is the list of tuples with test data. The third blank is the list of ID strings for each test case.

Practice

1. What is the main purpose of using ids in @pytest.mark.parametrize?

easy

A. To change the order of test execution

B. To skip certain test cases during execution

C. To label each test case for easier identification in reports

D. To automatically generate test data

Solution

1. Step 1: Understand the role of ids in parametrize

   The ids parameter assigns names to each test case, making it easier to identify which input caused a failure.

2. Step 2: Compare with other options

   Skipping tests, changing order, or generating data are not functions of ids.

3. Final Answer:

   To label each test case for easier identification in reports -> Option C

4. Quick Check:

   Parametrize ids = labels [OK]

Hint: IDs name test cases for clear failure reports [OK]

Common Mistakes:

• Thinking IDs skip tests
• Believing IDs reorder tests
• Assuming IDs generate data

2. Which of the following is the correct syntax to add IDs to a parametrize decorator in pytest?

easy

A. @pytest.mark.parametrize('x,y', [(1,2), (3,4)], ids=['first', 'second'])

B. @pytest.mark.parametrize('x,y', [(1,2), (3,4)], id=['first', 'second'])

C. @pytest.mark.parametrize('x,y', [(1,2), (3,4)], names=['first', 'second'])

D. @pytest.mark.parametrize('x,y', [(1,2), (3,4)], labels=['first', 'second'])

Solution

1. Step 1: Identify the correct parameter name

   The correct parameter to assign IDs is ids, not id, names, or labels.

2. Step 2: Check the syntax structure

   The syntax uses @pytest.mark.parametrize with the argument names, list of tuples, and ids as a list of strings.

3. Final Answer:

   @pytest.mark.parametrize('x,y', [(1,2), (3,4)], ids=['first', 'second']) -> Option A

4. Quick Check:

   Use ids parameter correctly [OK]

Hint: Use 'ids' keyword exactly for naming test cases [OK]

Common Mistakes:

• Using 'id' instead of 'ids'
• Using 'names' or 'labels' which are invalid
• Forgetting to pass a list for IDs

3. Given the code below, what will be the test ID shown for the second test case?

@pytest.mark.parametrize('num', [10, 20], ids=['ten', 'twenty'])
def test_value(num):
    assert num > 5

medium

A. test_value[twenty]

B. test_value[10]

C. test_value[1]

D. test_value[20]

Solution

1. Step 1: Understand how IDs map to test cases

   The ids list assigns 'ten' to the first input (10) and 'twenty' to the second input (20).

2. Step 2: Identify the second test case ID

   The second test case uses the second ID, which is 'twenty'.

3. Final Answer:

   test_value[twenty] -> Option A

4. Quick Check:

   Second ID label = 'twenty' [OK]

Hint: IDs replace values in test names [OK]

Common Mistakes:

• Assuming default numeric index is used
• Confusing value with ID label
• Ignoring the IDs parameter

4. Identify the error in the following pytest parametrize usage:

@pytest.mark.parametrize('a,b', [(1,2), (3,4)], ids='case1,case2')
def test_sum(a, b):
    assert a + b > 0

medium

A. Tuple values must be strings

B. Parameter names must be a list, not a string

C. Test function must return a value

D. IDs should be a list, not a single string

Solution

1. Step 1: Check the type of ids argument

   The ids parameter expects a list of strings, but here it is given a single string with commas.

2. Step 2: Understand the impact of wrong ids type

   Passing a string instead of a list causes pytest to treat it as an iterable of characters, leading to incorrect IDs or errors.

3. Final Answer:

   IDs should be a list, not a single string -> Option D

4. Quick Check:

   IDs must be list of strings [OK]

Hint: Pass IDs as list, not comma string [OK]

Common Mistakes:

• Passing comma-separated string instead of list
• Using wrong parameter type for IDs
• Confusing parameter names with IDs

5. You want to parametrize a test with inputs [(0, 'zero'), (1, 'one'), (2, 'two')] but want to skip the test case where the number is zero using IDs. Which approach correctly uses ids to help identify the skipped test case?

hard

A. @pytest.mark.parametrize('num,word', [(0,'zero'),(1,'one'),(2,'two')], ids=lambda val: f"skip_{val[0]}" if val[0]==0 else f"num_{val[0]}")

B. @pytest.mark.parametrize('num,word', [(0,'zero'),(1,'one'),(2,'two')], ids=['skip_zero', 'num_one', 'num_two'])

C. @pytest.mark.parametrize('num,word', [(0,'zero'),(1,'one'),(2,'two')], ids=['zero', 'one', 'two'])

D. @pytest.mark.parametrize('num,word', [(0,'zero'),(1,'one'),(2,'two')], ids=['num_0', 'num_1', 'num_2'])

Solution

1. Step 1: Understand the goal of IDs for skipping

   We want to label the zero case clearly as 'skip_zero' to identify it easily in reports.

2. Step 2: Evaluate each option's IDs usage

   @pytest.mark.parametrize('num,word', [(0,'zero'),(1,'one'),(2,'two')], ids=['skip_zero', 'num_one', 'num_two']) uses a list of strings with 'skip_zero' for zero, which is clear and correct. The lambda in @pytest.mark.parametrize('num,word', [(0,'zero'),(1,'one'),(2,'two')], ids=lambda val: f"skip_{val[0]}" if val[0]==0 else f"num_{val[0]}") is corrected to accept a single tuple argument as pytest passes. The options with ids=['num_0', 'num_1', 'num_2'] and ids=['zero', 'one', 'two'] do not label zero as skipped.

3. Final Answer:

   @pytest.mark.parametrize('num,word', [(0,'zero'),(1,'one'),(2,'two')], ids=['skip_zero', 'num_one', 'num_two']) -> Option B

4. Quick Check:

   Use explicit ID list to mark skipped case [OK]

Hint: Use explicit ID list to label skipped cases [OK]

Common Mistakes:

• Using lambda incorrectly for IDs
• Not labeling skipped cases clearly
• Using generic IDs without skip info