Spies vs Stubs

Developers should use spies when writing unit tests to monitor interactions with dependencies, such as external APIs, databases, or other modules, without stubbing or mocking their actual implementation meets developers should use stubs when writing unit tests to isolate the code being tested from external dependencies like databases, apis, or other modules, enabling faster and more predictable tests. Here's our take.

Spies

Nice Pick

Developers should use spies when writing unit tests to monitor interactions with dependencies, such as external APIs, databases, or other modules, without stubbing or mocking their actual implementation

Pros

• This is particularly useful for testing that certain functions are invoked as expected in scenarios like event handling, logging, or communication between components
• Related to: unit-testing, test-doubles

Cons

• Specific tradeoffs depend on your use case

Stubs

Developers should use stubs when writing unit tests to isolate the code being tested from external dependencies like databases, APIs, or other modules, enabling faster and more predictable tests

Pros

• They are particularly useful in scenarios where dependencies are slow, unreliable, or not yet implemented, such as in test-driven development (TDD) or when mocking complex interactions is unnecessary
• Related to: unit-testing, mocking

Cons

• Specific tradeoffs depend on your use case

The Verdict

Use Spies if: You want this is particularly useful for testing that certain functions are invoked as expected in scenarios like event handling, logging, or communication between components and can live with specific tradeoffs depend on your use case.

Use Stubs if: You prioritize they are particularly useful in scenarios where dependencies are slow, unreliable, or not yet implemented, such as in test-driven development (tdd) or when mocking complex interactions is unnecessary over what Spies offers.

The Bottom Line

Spies wins

Developers should use spies when writing unit tests to monitor interactions with dependencies, such as external APIs, databases, or other modules, without stubbing or mocking their actual implementation