unittest.mock.patch in PyTest - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of unittest.mock.patch in testing?

unittest.mock.patch temporarily replaces a part of your code (like a function or object) with a mock version during a test. This helps isolate the code you want to test by controlling dependencies.

beginner

How do you use patch as a decorator in pytest?

You add @patch('module_name.object_name') above your test function. The patched object is passed as an argument to your test, letting you control or check its behavior.

beginner

What does patching a function mean in simple terms?

It means swapping the real function with a fake one during a test. This fake function can return controlled results or track how it was called.

intermediate

What is the difference between patching with a decorator and patching with a context manager?

Decorator patching applies for the whole test function automatically. Context manager patching applies only inside a with block, giving more control over the patch duration.

intermediate

Why is it important to patch the object where it is used rather than where it is defined?

You patch where the object is looked up in your code, not where it was created. This ensures your patch replaces the exact reference your code uses during the test.

What does unittest.mock.patch do in a test?

A Compiles the code faster

B Deletes the object from the code

C Replaces a real object with a mock temporarily

D Runs the real function multiple times

patch swaps the real object with a mock during the test to control behavior.

How do you apply patch using a decorator in pytest?

A Inside the test function with <code>with patch()</code>

B @patch('module.object') above the test function

C By importing patch but not using it

D By calling patch after the test runs

Decorator patching uses @patch('module.object') before the test function.

Where should you patch an object to ensure it works correctly?

A Where the object is used in your code

B Where the object is originally defined

C Anywhere in the test file

D In a separate configuration file

Patching must happen where your code looks up the object, not where it was created.

What is a benefit of using patch as a context manager?

A Limits patching to a specific block of code

B Automatically patches all tests

C Makes the patch permanent

D Runs tests faster

Context manager patching applies only inside the with block, giving precise control.

What can you do with the mock object passed by patch decorator?

A Change the source code of the function

B Delete the original function permanently

C Run the original function faster

D Set return values and check how it was called

The mock lets you control return values and verify calls during tests.

Explain how unittest.mock.patch helps isolate code during testing.

Think about how you might replace a noisy part in a machine to test one part clearly.

Describe the difference between patching with a decorator and patching with a context manager.

Consider when you want the patch to start and stop.