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Kotlin Testing Patterns · loulanyue | DecimalAI

testingby loulanyue

Kotlin Testing Patterns

loulanyue/kotlin-testing

Source loulanyue/awesome-claude-notes ↗License MIT

Kotlin testing patterns with Kotest, MockK, coroutine testing, property-based testing, and Kover coverage. Follows TDD methodology with idiomatic Kotlin practices.

SkillScore100Maintained

Automatic

QA & Test Engineering pack

Last verified 8/22/2026

What it changes

Passed 22 of 22 test cases with the skill, and 16 of 22 without it.

Without skill73%

With skill100%

Checks it passed that the model alone missed

Configures the Kover plugin using version "0.9.7".
Uses Kotest FunSpec or DescribeSpec as the base spec style.
Uses Kotest StringSpec to structure the validator unit tests.

and 6 more in the full report

6 fixed16 passed either way0 still failing0 broke

Pass-rate lift: +27 pp
Tokens: +228%
Agent turns: 0%
Response time: -28%

Model gemini-3.6-flashMeasured 8/22/2026v622 of 22 cases passed with skill

Tokens, turns and time describe resource use, not a dollar price.

Use this skill

Save it into your project's skills folder. Claude Code picks it up in its next session.

curl -fsSL --create-dirs -o .claude/skills/loulanyue-kotlin-testing/SKILL.md https://app.decimal.ai/s/loulanyue-kotlin-testing/SKILL.md

Want it pinned and updatable? pip install "decimalai>=0.15", then decimalai skills add loulanyue-kotlin-testing, and start Claude Code with claude --plugin-dir "$(git rev-parse --show-toplevel)/.agents"

1 · One-time — install the CLI (docs ↗)

pip install "decimalai>=0.15"

2 · Get the skill — writes .agents/skills/loulanyue-kotlin-testing/ and pins it in .decimal/skills.lock

decimalai skills add loulanyue-kotlin-testing

No CLI? Get the same file — curl · raw file

curl -fsSL --create-dirs -o .claude/skills/loulanyue-kotlin-testing/SKILL.md https://app.decimal.ai/s/loulanyue-kotlin-testing/SKILL.md

Raw file: /s/loulanyue-kotlin-testing/SKILL.md ↗ · machine-readable summary at /s/loulanyue-kotlin-testing.json ↗

Safety checks: 3 of 3 passed

Code scan CleanIntent PassedContent Clean

See it in action

One of 6 test cases the skill fixed. Same model, same prompt, with and without the skill.

1 of 6

Prompt

Can you show me how to configure the Kover plugin inside build.gradle.kts to fail project builds when code coverage drops below a target percentage and generate report files? Also include the CLI commands for running coverage verification in Gradle.

What was checked, without and with the skill
Checked	Without skill	With skill
Configures the Kover plugin using version "0.9.7".	Missed	Passed
Includes a verify rule block specifying minBound(80) inside the kover build configuration.	Missed	Passed
Provides the CLI command ./gradlew koverVerify for running coverage verification.	Passed	Passed

case-01 · gemini-3.6-flash · 8/22/2026 · answers are capped and redacted

What's inside

The instructions your model reads when the skill loads.

SKILL.md825 linessingle file

Kotlin Testing Patterns

Comprehensive Kotlin testing patterns for writing reliable, maintainable tests following TDD methodology with Kotest and MockK.

When to Use

Writing new Kotlin functions or classes
Adding test coverage to existing Kotlin code
Implementing property-based tests
Following TDD workflow in Kotlin projects
Configuring Kover for code coverage

How It Works

Identify target code — Find the function, class, or module to test
Write a Kotest spec — Choose a spec style (StringSpec, FunSpec, BehaviorSpec) matching the test scope
Mock dependencies — Use MockK to isolate the unit under test
Run tests (RED) — Verify the test fails with the expected error
Implement code (GREEN) — Write minimal code to pass the test
Refactor — Improve the implementation while keeping tests green
Check coverage — Run ./gradlew koverHtmlReport and verify 80%+ coverage

Examples

The following sections contain detailed, runnable examples for each testing pattern:

Quick Reference

Kotest specs — StringSpec, FunSpec, BehaviorSpec, DescribeSpec examples in Kotest Spec Styles
Mocking — MockK setup, coroutine mocking, argument capture in MockK
TDD walkthrough — Full RED/GREEN/REFACTOR cycle with EmailValidator in TDD Workflow for Kotlin
Coverage — Kover configuration and commands in Kover Coverage
Ktor testing — testApplication setup in Ktor testApplication Testing

TDD Workflow for Kotlin

The RED-GREEN-REFACTOR Cycle

RED     -> Write a failing test first

Track record

Benchmark

22 / 22

test cases passed, vs 16 / 22 without

Adoption

Users: 0
Times used: 0

Safety and source details

SkillSafety

✓ 3 of 3 passed

Code scan15 of 15 checks clean

0 critical · 0 warning · 0 info — scanner v4 — 8/3/2026

View 15 scanner checks

live_secretremote_code_executionreverse_shelldata_exfiltrationssrf_metadataagent_snoopinganti_refusaldestructive_commandsobfuscated_unicodeunicode_homoglyphopaque_blobsuspicious_urltool_overreachtrigger_abuseprompt_injection_phrasing

IntentSafe

LLM judge · does the skill do what it claims

ContentClean

LLM judge · policy & harmful-content review

Source

Imported

loulanyue / awesome-claude-notes

docs/ja-JP/skills/kotlin-testing/SKILL.md

View on GitHub ↗

License MITImported 8/3/2026Version v6

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See it in action

What's inside

Kotlin Testing Patterns

When to Use

How It Works

Examples

Quick Reference

TDD Workflow for Kotlin

The RED-GREEN-REFACTOR Cycle

Track record

Benchmark

Adoption

SkillSafety

Source

Other skills for the same job

Related skills