Test discovery rules in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to name a test function that pytest will discover automatically.

PyTest

def [1]():
    assert 1 + 1 == 2

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

Atest_addition

Baddition_test

Ccheck_addition

DAddTest

Attempts:

3 left

💡 Hint

Common Mistakes

Naming the function without 'test_' prefix

Using camel case starting with uppercase

Pytest discovers test functions that start with test_. So test_addition is correct.

2fill in blank

medium

Complete the code to name a test file that pytest will discover automatically.

PyTest

# File name: [1]

def test_example():
    assert True

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

Aexample_test.py

BTestExample.py

Ctest_example.py

Dexample.py

Attempts:

3 left

💡 Hint

Common Mistakes

Naming file without 'test_' prefix or '_test' suffix

Using uppercase letters in file name

Pytest discovers test files that start with test_ or end with _test.py. Here, test_example.py is correct.

3fill in blank

hard

Fix the error in the test class name so pytest will discover its test methods.

PyTest

class [1]:
    def test_method(self):
        assert True

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

Amytest

BTestMyClass

CMyTests

DTests

Attempts:

3 left

💡 Hint

Common Mistakes

Class name not starting with 'Test'

Using lowercase class names

Pytest discovers test classes that start with Test and do not have an __init__ method. So TestMyClass is correct.

4fill in blank

hard

Fill both blanks to create a test function that pytest will discover and run.

PyTest

def [1]([2]):
    assert [2] > 0

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

Atest_positive

Bvalue

Ccheck_positive

Dnum

Attempts:

3 left

💡 Hint

Common Mistakes

Function name not starting with 'test_'

Using invalid parameter names

The function name must start with test_ and the parameter can be any valid name, here value is used.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that filters test data for pytest.

PyTest

filtered = { [1]: [2] for [1] in data if [2] [3] 10 }

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

Akey

Bvalue

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using same variable name for key and value

Wrong comparison operator

The comprehension uses key and value as variable names, and filters values greater than 10 using >.

Practice

1. Which of the following file names will pytest recognize as a test file by default?

easy

A. example.py

B. test_example.py

C. example_test.pyc

D. TestExample.py

Solution

1. Step 1: Understand pytest file naming rules

   pytest looks for files starting or ending with 'test' and ending with '.py'.

2. Step 2: Check each option

   'test_example.py' starts with 'test' and ends with '.py', so pytest will find it. Others either don't end with '.py' or don't start/end with 'test'.

3. Final Answer:

   test_example.py -> Option B

4. Quick Check:

   File starts or ends with 'test' + '.py' = test_example.py [OK]

Hint: Test files start or end with 'test' and end with '.py' [OK]

Common Mistakes:

• Thinking pytest finds .pyc files
• Ignoring case sensitivity in file names
• Assuming any .py file is a test file

2. Which function name will pytest recognize as a test function by default?

easy

A. test_login()

B. testLogin()

C. check_login()

D. login_test()

Solution

1. Step 1: Recall pytest test function naming

   pytest looks for functions starting with 'test_'.

2. Step 2: Evaluate each function name

   'test_login()' starts with 'test_' exactly, so pytest will find it. Others do not follow this pattern.

3. Final Answer:

   test_login() -> Option A

4. Quick Check:

   Function starts with 'test_' = test_login() [OK]

Hint: Test functions start with 'test_' exactly [OK]

Common Mistakes:

• Using camelCase instead of snake_case
• Placing 'test' at the end of function name
• Missing underscore after 'test'

3. Given the following files and functions, which tests will pytest discover and run?

File: test_math.py
  def test_add(): pass
  def add_test(): pass

File: math_test.py
  def test_subtract(): pass
  def subtract_test(): pass

File: math.py
  def test_multiply(): pass

medium

A. test_add, test_subtract

B. test_add, test_subtract, test_multiply

C. test_add, subtract_test

D. add_test, subtract_test

Solution

1. Step 1: Identify test files pytest finds

   pytest finds files starting or ending with 'test' and ending with '.py'. So 'test_math.py' and 'math_test.py' are test files. 'math.py' is not.

2. Step 2: Identify test functions pytest finds in those files

   In 'test_math.py', pytest finds 'test_add' (starts with 'test_'). 'add_test' is ignored. In 'math_test.py', pytest finds 'test_subtract'. 'subtract_test' is ignored. 'test_multiply' in 'math.py' is ignored because file is not a test file.

3. Final Answer:

   test_add, test_subtract -> Option A

4. Quick Check:

   Files and functions follow naming rules = test_add, test_subtract [OK]

Hint: Test files and functions must follow naming rules to be discovered [OK]

Common Mistakes:

• Assuming any function starting with 'test' is found regardless of file name
• Including functions in non-test files
• Confusing function name endings with beginnings

4. You have a test file named TestExample.py with a function def test_func():. pytest does not run this test. What is the likely cause?

medium

A. Function name does not start with 'test_'

B. pytest requires test classes to run tests

C. File name does not follow pytest discovery rules

D. Function is missing a return statement

Solution

1. Step 1: Check pytest file discovery rules

   pytest finds files starting or ending with 'test' in lowercase and ending with '.py'. 'TestExample.py' starts with uppercase 'T', so it is not recognized.

2. Step 2: Verify function name and other options

   Function name 'test_func' is correct. Return statement is not required. pytest does not require test classes to run functions.

3. Final Answer:

   File name does not follow pytest discovery rules -> Option C

4. Quick Check:

   File name case-sensitive for discovery = D [OK]

Hint: File names must be lowercase starting or ending with 'test' [OK]

Common Mistakes:

• Ignoring case sensitivity in file names
• Thinking function needs return statement
• Assuming test classes are mandatory

5. You want pytest to discover tests in a file named mytests.py containing functions def test_one(): and def test_two():. By default, pytest does not find this file. How can you rename the file to follow pytest discovery rules without changing function names?

hard

A. Rename to my_test_s.py

B. Rename to mytestsTest.py

C. Rename to testmytests.py

D. Rename to test_mytests.py

Solution

1. Step 1: Recall pytest file discovery naming

   pytest finds files starting with 'test_' or ending with '_test.py'.

2. Step 2: Check options for correct naming

   'test_mytests.py' starts with 'test_' [check]. 'mytestsTest.py' ends with 'Test.py' (uppercase 'T' not matching lowercase 'test'). 'testmytests.py' lacks '_' after 'test'. 'my_test_s.py' does not start with 'test_' or end with '_test.py'. Only the first option works.

3. Final Answer:

   Rename to test_mytests.py -> Option D

4. Quick Check:

   File starts or ends with 'test' = test_mytests.py [OK]

Hint: File must start or end with 'test' exactly [OK]

Common Mistakes:

• Removing 'test' from file name
• Adding 'test' inside word without underscore
• Using camelCase instead of snake_case