Structure Kotlin tests with fakes, Object Mothers, and TestClock.
npx skills add https://github.com/anderssv/the-example --skill kotlin-tdd
Please help me install this Agent Skill. Skill: kotlin-tdd Source: https://github.com/anderssv/the-example/tree/main/skills/testing/kotlin-tdd Command: npx skills add https://github.com/anderssv/the-example --skill kotlin-tdd
It solves the problem of brittle, flaky Kotlin tests by guiding you to set up state predictably with fakes and to drive scenarios through domain behavior instead of direct data manipulation.
.copy() to create consistent domain state quickly.TestClock to deterministically test time-based behavior like expiration and scheduling.Real-world use cases include writing stable TDD-style test scaffolding for service workflows, verifying end-to-end-ish outcomes across domain operations with in-memory fakes, and testing time-dependent rules without waiting in real time.
Ask Claude to help you write a Kotlin test using SystemTestContext with fakes, create domain input with valid() Object Mothers, control time with TestClock if needed, and verify outcomes via domain operations (TTTD) instead of repository state setup.
High-intent search queries and answers about installing and using this skill.
Fakes behave like real implementations using HashMap-based state, enabling state-based assertions without mocking frameworks. This keeps tests deterministic and readable while verifying outcomes through actual domain behavior rather than framework interactions.
Testing Through The Domain (TTTD) populates and verifies system state via domain operations like register and approve flows instead of direct data manipulation. This makes tests survive domain evolution by driving scenarios through actual behavior rather than direct repository state setup.
Use a TestClock to deterministically test time-based behavior like expiration and scheduling without real-time delays. Inject it through SystemTestContext to control time progression in your Kotlin tests and verify time-dependent rules predictably.
Fakes are preferred over mocks for Kotlin TDD because HashMap-based fakes behave like real implementations and enable state-based assertions without mocking frameworks. This approach supports end-to-end-ish outcome verification across domain operations with deterministic in-memory behavior.
Use real implementations for domain logic that benefits from end-to-end verification, but switch to in-memory fakes for external repositories and clients. Inject fakes through SystemTestContext when testing service workflows requiring predictable state setup and controllable dependencies like TestClock.
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