What is the practical difference between a fake, a mock, and a stub in Flutter tests?

Short answer

A test double replaces a dependency; a fake is a simple working implementation, a stub returns fixed answers, and a mock verifies expected interactions.

Explanation

Choose the simplest double that proves the required behavior. A fake repository is often sturdier than expecting dozens of calls, and a mock is useful when the interaction itself is an important contract; do not test details that do not matter to the user.

Common mistakes

• Mocking every dependency until refactoring becomes impossible.
• Using a fake that does not resemble the real failure modes when they are needed.

Follow-up questions

• What is the role of an integration test and when is it worth its cost?

Sources

• Flutter docs — Mock dependencies