Direct inputs

The inputs that a SUT directly receives via it's interface (i.e method parameters)

Direct outputs

The outputs a SUT directly returns via it's interface (i.e method return values)

Dummy

Test double that is never used or called but must be present (i.e it could just be null)

Fake

Test double that acts as a lightweight stand in for some other component

• 4.18. Only Unit Test Code It Makes Sense To Unit Test

Guava

An open source project from Google that provides common utilities for Java such as collections operations, string processing and caching. Originally known as Google Collections.

• 3.5. Prefer Maps And Filters To Imperative Loops
• 3.1. Know How To Implement Hashcode And Equals
• 3.9. Do Not Use The Assert Keyword
• 2.15. Avoid Null
• 2.18. Avoid Checked Exceptions

Indirect inputs

Inputs supplied to the SUT by other components with which it interacts (i.e values supplied by DOCs)

Indirect outputs

Outputs of the SUT that are passed to DOCs but are not visible via the SUT interface

Mock

Test double that verifies indirect outputs from SUT (may also provide indirect input)

• 2.5. Prefer Composition
• 2.9. Make Dependencies Explicit
• 4.18. Only Unit Test Code It Makes Sense To Unit Test

Spy

Test double that captures indirect outputs from SUT to allow later verification (may also provide indirect input)

Stub

Test double that supplies indirect inputs to SUT (and does nothing else)

• 2.9. Make Dependencies Explicit

SUT

System under test

• 4.16. Choose Carefully Between State And Interaction Testing

TDD

Test driven development or Test driven design.

• 3.9. Do Not Use The Assert Keyword

Test double

Generic names for Dummy, Stub, Spy, Fake or Mock