monkeypatch.setattr in PyTest - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is monkeypatch.setattr used for in pytest?

<p><code>monkeypatch.setattr</code> temporarily replaces an attribute or method in a module or class during a test. It helps simulate different behaviors without changing the real code.</p>

beginner

How does monkeypatch.setattr help in testing functions that depend on external resources?

It allows you to replace calls to external resources (like APIs or databases) with fake functions or values. This makes tests faster and more reliable by avoiding real external calls.

beginner

Example: What does this code do?<br>

monkeypatch.setattr('os.path.exists', lambda path: True)

This replaces the os.path.exists function with a fake one that always returns True. So, any code checking if a file exists will think it does.

intermediate

What happens to the original attribute after the test using monkeypatch.setattr finishes?

The original attribute is restored automatically after the test ends. This keeps tests isolated and prevents side effects on other tests.

intermediate

Can monkeypatch.setattr be used to patch instance attributes as well as module-level functions?

Yes, it can patch both instance attributes and module-level functions or variables by specifying the target correctly.

What does monkeypatch.setattr do in pytest?

A Runs tests in parallel

B Permanently changes the source code

C Temporarily replaces an attribute or method during a test

D Generates test reports

monkeypatch.setattr temporarily replaces attributes or methods only during the test execution.

After using monkeypatch.setattr, what happens to the original attribute after the test ends?

A It is restored automatically

B It is deleted

C It causes an error

D It stays replaced

The original attribute is restored automatically to keep tests isolated.

Which of these is a good use case for monkeypatch.setattr?

A Replacing a function that calls an external API with a fake one

B Changing the Python interpreter version

C Modifying test runner settings

D Writing new test cases

Replacing external calls with fake functions makes tests faster and more reliable.

How do you specify the target to patch with monkeypatch.setattr?

A By creating a new test file

B By editing the source code file

C By running a shell command

D By giving the full import path as a string or the object and attribute name

You specify the target by its import path string or by passing the object and attribute name.

Can monkeypatch.setattr patch instance attributes?

A No, only module-level functions

B Yes, if the target is specified correctly

C Only for classes, not instances

D Only for built-in types

It can patch instance attributes if you specify the correct target.

Explain how monkeypatch.setattr helps in writing tests that avoid calling real external services.

Think about how you can fake parts of your code during tests.

Describe the steps to use monkeypatch.setattr to replace a method in a module for a test.

Focus on how you specify what to patch and what to replace it with.