AgentSkillsCN

red-green-refactor

TDD 红—绿—重构周期指南。在采用测试驱动开发时，按照“编写失败的测试（Red）→以最少代码通过测试（Green）→进行重构（Refactor）”的顺序执行。该指南适用于基于 Kotest DescribeSpec 的 Kotlin/JVM 项目，帮助开发者在实践中践行 TDD 开发模式。

SKILL.md
--- frontmatter
name: red-green-refactor
description: TDD Red-Green-Refactor 사이클 가이드. 테스트 주도 개발 시 실패하는 테스트 작성(Red), 최소한의 코드로 통과(Green), 리팩토링(Refactor) 순서를 따를 때 사용. Kotest DescribeSpec 기반 Kotlin/JVM 프로젝트에서 TDD 실천 시 활용.

TDD Red-Green-Refactor Cycle

Red Phase: Write Failing Test

  1. •Express intended behavior as test first
  2. •Test only one behavior at a time
  3. •Must verify failure by running test (compilation errors count as failures)
kotlin
// Kotest DescribeSpec example
class CalculatorTest : DescribeSpec({
    describe("Calculator") {
        it("두 숫자를 더한다") {
            val calculator = Calculator()
            calculator.add(2, 3) shouldBe 5
        }
    }
})

Verify failure message matches intent. Unexpected failure reasons indicate test issues.

Green Phase: Make Test Pass

  1. •Write minimal code to pass the test
  2. •Hardcoding, duplication, messy code allowed
  3. •Goal is only green bar
kotlin
class Calculator {
    fun add(a: Int, b: Int): Int = 5  // Hardcoding OK
}

"Working code" first, "clean code" next.

Refactor Phase: Improve Code

  1. •Keep tests passing while improving
  2. •Remove duplication, improve naming, apply patterns
  3. •Must re-run tests after refactoring
  4. •No new features - structural improvements only
kotlin
class Calculator {
    fun add(a: Int, b: Int): Int = a + b  // Generalize
}

Cycle Rules

  • •No production code without test
  • •No production code changes without failing test
  • •Commit after passing tests (keep commits small)
  • •No new features during refactoring
  • •Minimize test changes during refactoring

Checklist

Red

  • • Test verifies single behavior?
  • • Verified failure by running test?
  • • Failure message as intended?

Green

  • • Passed with simplest approach?
  • • Test is green?

Refactor

  • • Tests still green?
  • • Duplication removed?
  • • Names reveal intent?
  • • No new features added?