docs(zh-CN): update

2026-04-14 13:53:29 +08:00 · 2026-03-13 17:45:44 +08:00
parent f548ca3e19
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+---
+name: kotlin-testing
+description: 使用Kotest、MockK、协程测试、基于属性的测试和Kover覆盖率的Kotlin测试模式。遵循TDD方法论和地道的Kotlin实践。
+origin: ECC
+---
+
+# Kotlin 测试模式
+
+遵循 TDD 方法论，使用 Kotest 和 MockK 编写可靠、可维护测试的全面 Kotlin 测试模式。
+
+## 何时使用
+
+* 编写新的 Kotlin 函数或类
+* 为现有 Kotlin 代码添加测试覆盖率
+* 实现基于属性的测试
+* 在 Kotlin 项目中遵循 TDD 工作流
+* 为代码覆盖率配置 Kover
+
+## 工作原理
+
+1. **确定目标代码** — 找到要测试的函数、类或模块
+2. **编写 Kotest 规范** — 选择与测试范围匹配的规范样式（StringSpec、FunSpec、BehaviorSpec）
+3. **模拟依赖项** — 使用 MockK 来隔离被测单元
+4. **运行测试（红色阶段）** — 验证测试是否按预期失败
+5. **实现代码（绿色阶段）** — 编写最少的代码以使测试通过
+6. **重构** — 改进实现，同时保持测试通过
+7. **检查覆盖率** — 运行 `./gradlew koverHtmlReport` 并验证 80%+ 的覆盖率
+
+## 示例
+
+以下部分包含每个测试模式的详细、可运行示例：
+
+### 快速参考
+
+* **Kotest 规范** — [Kotest 规范样式](#kotest-规范样式) 中的 StringSpec、FunSpec、BehaviorSpec、DescribeSpec 示例
+* **模拟** — [MockK](#mockk) 中的 MockK 设置、协程模拟、参数捕获
+* **TDD 演练** — [Kotlin 的 TDD 工作流](#kotlin-的-tdd-工作流) 中 EmailValidator 的完整 RED/GREEN/REFACTOR 周期
+* **覆盖率** — [Kover 覆盖率](#kover-覆盖率) 中的 Kover 配置和命令
+* **Ktor 测试** — [Ktor testApplication 测试](#ktor-testapplication-测试) 中的 testApplication 设置
+
+### Kotlin 的 TDD 工作流
+
+#### RED-GREEN-REFACTOR 周期
+
+```
+RED     -> Write a failing test first
+GREEN   -> Write minimal code to pass the test
+REFACTOR -> Improve code while keeping tests green
+REPEAT  -> Continue with next requirement
+```
+
+#### Kotlin 中逐步进行 TDD
+
+```kotlin
+// Step 1: Define the interface/signature
+// EmailValidator.kt
+package com.example.validator
+
+fun validateEmail(email: String): Result<String> {
+    TODO("not implemented")
+}
+
+// Step 2: Write failing test (RED)
+// EmailValidatorTest.kt
+package com.example.validator
+
+import io.kotest.core.spec.style.StringSpec
+import io.kotest.matchers.result.shouldBeFailure
+import io.kotest.matchers.result.shouldBeSuccess
+
+class EmailValidatorTest : StringSpec({
+    "valid email returns success" {
+        validateEmail("user@example.com").shouldBeSuccess("user@example.com")
+    }
+
+    "empty email returns failure" {
+        validateEmail("").shouldBeFailure()
+    }
+
+    "email without @ returns failure" {
+        validateEmail("userexample.com").shouldBeFailure()
+    }
+})
+
+// Step 3: Run tests - verify FAIL
+// $ ./gradlew test
+// EmailValidatorTest > valid email returns success FAILED
+//   kotlin.NotImplementedError: An operation is not implemented
+
+// Step 4: Implement minimal code (GREEN)
+fun validateEmail(email: String): Result<String> {
+    if (email.isBlank()) return Result.failure(IllegalArgumentException("Email cannot be blank"))
+    if ('@' !in email) return Result.failure(IllegalArgumentException("Email must contain @"))
+    val regex = Regex("^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}$")
+    if (!regex.matches(email)) return Result.failure(IllegalArgumentException("Invalid email format"))
+    return Result.success(email)
+}
+
+// Step 5: Run tests - verify PASS
+// $ ./gradlew test
+// EmailValidatorTest > valid email returns success PASSED
+// EmailValidatorTest > empty email returns failure PASSED
+// EmailValidatorTest > email without @ returns failure PASSED
+
+// Step 6: Refactor if needed, verify tests still pass
+```
+
+### Kotest 规范样式
+
+#### StringSpec（最简单）
+
+```kotlin
+class CalculatorTest : StringSpec({
+    "add two positive numbers" {
+        Calculator.add(2, 3) shouldBe 5
+    }
+
+    "add negative numbers" {
+        Calculator.add(-1, -2) shouldBe -3
+    }
+
+    "add zero" {
+        Calculator.add(0, 5) shouldBe 5
+    }
+})
+```
+
+#### FunSpec（类似 JUnit）
+
+```kotlin
+class UserServiceTest : FunSpec({
+    val repository = mockk<UserRepository>()
+    val service = UserService(repository)
+
+    test("getUser returns user when found") {
+        val expected = User(id = "1", name = "Alice")
+        coEvery { repository.findById("1") } returns expected
+
+        val result = service.getUser("1")
+
+        result shouldBe expected
+    }
+
+    test("getUser throws when not found") {
+        coEvery { repository.findById("999") } returns null
+
+        shouldThrow<UserNotFoundException> {
+            service.getUser("999")
+        }
+    }
+})
+```
+
+#### BehaviorSpec（BDD 风格）
+
+```kotlin
+class OrderServiceTest : BehaviorSpec({
+    val repository = mockk<OrderRepository>()
+    val paymentService = mockk<PaymentService>()
+    val service = OrderService(repository, paymentService)
+
+    Given("a valid order request") {
+        val request = CreateOrderRequest(
+            userId = "user-1",
+            items = listOf(OrderItem("product-1", quantity = 2)),
+        )
+
+        When("the order is placed") {
+            coEvery { paymentService.charge(any()) } returns PaymentResult.Success
+            coEvery { repository.save(any()) } answers { firstArg() }
+
+            val result = service.placeOrder(request)
+
+            Then("it should return a confirmed order") {
+                result.status shouldBe OrderStatus.CONFIRMED
+            }
+
+            Then("it should charge payment") {
+                coVerify(exactly = 1) { paymentService.charge(any()) }
+            }
+        }
+
+        When("payment fails") {
+            coEvery { paymentService.charge(any()) } returns PaymentResult.Declined
+
+            Then("it should throw PaymentException") {
+                shouldThrow<PaymentException> {
+                    service.placeOrder(request)
+                }
+            }
+        }
+    }
+})
+```
+
+#### DescribeSpec（RSpec 风格）
+
+```kotlin
+class UserValidatorTest : DescribeSpec({
+    describe("validateUser") {
+        val validator = UserValidator()
+
+        context("with valid input") {
+            it("accepts a normal user") {
+                val user = CreateUserRequest("Alice", "alice@example.com")
+                validator.validate(user).shouldBeValid()
+            }
+        }
+
+        context("with invalid name") {
+            it("rejects blank name") {
+                val user = CreateUserRequest("", "alice@example.com")
+                validator.validate(user).shouldBeInvalid()
+            }
+
+            it("rejects name exceeding max length") {
+                val user = CreateUserRequest("A".repeat(256), "alice@example.com")
+                validator.validate(user).shouldBeInvalid()
+            }
+        }
+    }
+})
+```
+
+### Kotest 匹配器
+
+#### 核心匹配器
+
+```kotlin
+import io.kotest.matchers.shouldBe
+import io.kotest.matchers.shouldNotBe
+import io.kotest.matchers.string.*
+import io.kotest.matchers.collections.*
+import io.kotest.matchers.nulls.*
+
+// Equality
+result shouldBe expected
+result shouldNotBe unexpected
+
+// Strings
+name shouldStartWith "Al"
+name shouldEndWith "ice"
+name shouldContain "lic"
+name shouldMatch Regex("[A-Z][a-z]+")
+name.shouldBeBlank()
+
+// Collections
+list shouldContain "item"
+list shouldHaveSize 3
+list.shouldBeSorted()
+list.shouldContainAll("a", "b", "c")
+list.shouldBeEmpty()
+
+// Nulls
+result.shouldNotBeNull()
+result.shouldBeNull()
+
+// Types
+result.shouldBeInstanceOf<User>()
+
+// Numbers
+count shouldBeGreaterThan 0
+price shouldBeInRange 1.0..100.0
+
+// Exceptions
+shouldThrow<IllegalArgumentException> {
+    validateAge(-1)
+}.message shouldBe "Age must be positive"
+
+shouldNotThrow<Exception> {
+    validateAge(25)
+}
+```
+
+#### 自定义匹配器
+
+```kotlin
+fun beActiveUser() = object : Matcher<User> {
+    override fun test(value: User) = MatcherResult(
+        value.isActive && value.lastLogin != null,
+        { "User ${value.id} should be active with a last login" },
+        { "User ${value.id} should not be active" },
+    )
+}
+
+// Usage
+user should beActiveUser()
+```
+
+### MockK
+
+#### 基本模拟
+
+```kotlin
+class UserServiceTest : FunSpec({
+    val repository = mockk<UserRepository>()
+    val logger = mockk<Logger>(relaxed = true) // Relaxed: returns defaults
+    val service = UserService(repository, logger)
+
+    beforeTest {
+        clearMocks(repository, logger)
+    }
+
+    test("findUser delegates to repository") {
+        val expected = User(id = "1", name = "Alice")
+        every { repository.findById("1") } returns expected
+
+        val result = service.findUser("1")
+
+        result shouldBe expected
+        verify(exactly = 1) { repository.findById("1") }
+    }
+
+    test("findUser returns null for unknown id") {
+        every { repository.findById(any()) } returns null
+
+        val result = service.findUser("unknown")
+
+        result.shouldBeNull()
+    }
+})
+```
+
+#### 协程模拟
+
+```kotlin
+class AsyncUserServiceTest : FunSpec({
+    val repository = mockk<UserRepository>()
+    val service = UserService(repository)
+
+    test("getUser suspending function") {
+        coEvery { repository.findById("1") } returns User(id = "1", name = "Alice")
+
+        val result = service.getUser("1")
+
+        result.name shouldBe "Alice"
+        coVerify { repository.findById("1") }
+    }
+
+    test("getUser with delay") {
+        coEvery { repository.findById("1") } coAnswers {
+            delay(100) // Simulate async work
+            User(id = "1", name = "Alice")
+        }
+
+        val result = service.getUser("1")
+        result.name shouldBe "Alice"
+    }
+})
+```
+
+#### 参数捕获
+
+```kotlin
+test("save captures the user argument") {
+    val slot = slot<User>()
+    coEvery { repository.save(capture(slot)) } returns Unit
+
+    service.createUser(CreateUserRequest("Alice", "alice@example.com"))
+
+    slot.captured.name shouldBe "Alice"
+    slot.captured.email shouldBe "alice@example.com"
+    slot.captured.id.shouldNotBeNull()
+}
+```
+
+#### 间谍和部分模拟
+
+```kotlin
+test("spy on real object") {
+    val realService = UserService(repository)
+    val spy = spyk(realService)
+
+    every { spy.generateId() } returns "fixed-id"
+
+    spy.createUser(request)
+
+    verify { spy.generateId() } // Overridden
+    // Other methods use real implementation
+}
+```
+
+### 协程测试
+
+#### 用于挂起函数的 runTest
+
+```kotlin
+import kotlinx.coroutines.test.runTest
+
+class CoroutineServiceTest : FunSpec({
+    test("concurrent fetches complete together") {
+        runTest {
+            val service = DataService(testScope = this)
+
+            val result = service.fetchAllData()
+
+            result.users.shouldNotBeEmpty()
+            result.products.shouldNotBeEmpty()
+        }
+    }
+
+    test("timeout after delay") {
+        runTest {
+            val service = SlowService()
+
+            shouldThrow<TimeoutCancellationException> {
+                withTimeout(100) {
+                    service.slowOperation() // Takes > 100ms
+                }
+            }
+        }
+    }
+})
+```
+
+#### 测试 Flow
+
+```kotlin
+import io.kotest.matchers.collections.shouldContainInOrder
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.toList
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.test.advanceTimeBy
+import kotlinx.coroutines.test.runTest
+
+class FlowServiceTest : FunSpec({
+    test("observeUsers emits updates") {
+        runTest {
+            val service = UserFlowService()
+
+            val emissions = service.observeUsers()
+                .take(3)
+                .toList()
+
+            emissions shouldHaveSize 3
+            emissions.last().shouldNotBeEmpty()
+        }
+    }
+
+    test("searchUsers debounces input") {
+        runTest {
+            val service = SearchService()
+            val queries = MutableSharedFlow<String>()
+
+            val results = mutableListOf<List<User>>()
+            val job = launch {
+                service.searchUsers(queries).collect { results.add(it) }
+            }
+
+            queries.emit("a")
+            queries.emit("ab")
+            queries.emit("abc") // Only this should trigger search
+            advanceTimeBy(500)
+
+            results shouldHaveSize 1
+            job.cancel()
+        }
+    }
+})
+```
+
+#### TestDispatcher
+
+```kotlin
+import kotlinx.coroutines.test.StandardTestDispatcher
+import kotlinx.coroutines.test.advanceUntilIdle
+
+class DispatcherTest : FunSpec({
+    test("uses test dispatcher for controlled execution") {
+        val dispatcher = StandardTestDispatcher()
+
+        runTest(dispatcher) {
+            var completed = false
+
+            launch {
+                delay(1000)
+                completed = true
+            }
+
+            completed shouldBe false
+            advanceTimeBy(1000)
+            completed shouldBe true
+        }
+    }
+})
+```
+
+### 基于属性的测试
+
+#### Kotest 属性测试
+
+```kotlin
+import io.kotest.core.spec.style.FunSpec
+import io.kotest.property.Arb
+import io.kotest.property.arbitrary.*
+import io.kotest.property.forAll
+import io.kotest.property.checkAll
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.decodeFromString
+
+// Note: The serialization roundtrip test below requires the User data class
+// to be annotated with @Serializable (from kotlinx.serialization).
+
+class PropertyTest : FunSpec({
+    test("string reverse is involutory") {
+        forAll<String> { s ->
+            s.reversed().reversed() == s
+        }
+    }
+
+    test("list sort is idempotent") {
+        forAll(Arb.list(Arb.int())) { list ->
+            list.sorted() == list.sorted().sorted()
+        }
+    }
+
+    test("serialization roundtrip preserves data") {
+        checkAll(Arb.bind(Arb.string(1..50), Arb.string(5..100)) { name, email ->
+            User(name = name, email = "$email@test.com")
+        }) { user ->
+            val json = Json.encodeToString(user)
+            val decoded = Json.decodeFromString<User>(json)
+            decoded shouldBe user
+        }
+    }
+})
+```
+
+#### 自定义生成器
+
+```kotlin
+val userArb: Arb<User> = Arb.bind(
+    Arb.string(minSize = 1, maxSize = 50),
+    Arb.email(),
+    Arb.enum<Role>(),
+) { name, email, role ->
+    User(
+        id = UserId(UUID.randomUUID().toString()),
+        name = name,
+        email = Email(email),
+        role = role,
+    )
+}
+
+val moneyArb: Arb<Money> = Arb.bind(
+    Arb.long(1L..1_000_000L),
+    Arb.enum<Currency>(),
+) { amount, currency ->
+    Money(amount, currency)
+}
+```
+
+### 数据驱动测试
+
+#### Kotest 中的 withData
+
+```kotlin
+class ParserTest : FunSpec({
+    context("parsing valid dates") {
+        withData(
+            "2026-01-15" to LocalDate(2026, 1, 15),
+            "2026-12-31" to LocalDate(2026, 12, 31),
+            "2000-01-01" to LocalDate(2000, 1, 1),
+        ) { (input, expected) ->
+            parseDate(input) shouldBe expected
+        }
+    }
+
+    context("rejecting invalid dates") {
+        withData(
+            nameFn = { "rejects '$it'" },
+            "not-a-date",
+            "2026-13-01",
+            "2026-00-15",
+            "",
+        ) { input ->
+            shouldThrow<DateParseException> {
+                parseDate(input)
+            }
+        }
+    }
+})
+```
+
+### 测试生命周期和固件
+
+#### BeforeTest / AfterTest
+
+```kotlin
+class DatabaseTest : FunSpec({
+    lateinit var db: Database
+
+    beforeSpec {
+        db = Database.connect("jdbc:h2:mem:test;DB_CLOSE_DELAY=-1")
+        transaction(db) {
+            SchemaUtils.create(UsersTable)
+        }
+    }
+
+    afterSpec {
+        transaction(db) {
+            SchemaUtils.drop(UsersTable)
+        }
+    }
+
+    beforeTest {
+        transaction(db) {
+            UsersTable.deleteAll()
+        }
+    }
+
+    test("insert and retrieve user") {
+        transaction(db) {
+            UsersTable.insert {
+                it[name] = "Alice"
+                it[email] = "alice@example.com"
+            }
+        }
+
+        val users = transaction(db) {
+            UsersTable.selectAll().map { it[UsersTable.name] }
+        }
+
+        users shouldContain "Alice"
+    }
+})
+```
+
+#### Kotest 扩展
+
+```kotlin
+// Reusable test extension
+class DatabaseExtension : BeforeSpecListener, AfterSpecListener {
+    lateinit var db: Database
+
+    override suspend fun beforeSpec(spec: Spec) {
+        db = Database.connect("jdbc:h2:mem:test;DB_CLOSE_DELAY=-1")
+    }
+
+    override suspend fun afterSpec(spec: Spec) {
+        // cleanup
+    }
+}
+
+class UserRepositoryTest : FunSpec({
+    val dbExt = DatabaseExtension()
+    register(dbExt)
+
+    test("save and find user") {
+        val repo = UserRepository(dbExt.db)
+        // ...
+    }
+})
+```
+
+### Kover 覆盖率
+
+#### Gradle 配置
+
+```kotlin
+// build.gradle.kts
+plugins {
+    id("org.jetbrains.kotlinx.kover") version "0.9.7"
+}
+
+kover {
+    reports {
+        total {
+            html { onCheck = true }
+            xml { onCheck = true }
+        }
+        filters {
+            excludes {
+                classes("*.generated.*", "*.config.*")
+            }
+        }
+        verify {
+            rule {
+                minBound(80) // Fail build below 80% coverage
+            }
+        }
+    }
+}
+```
+
+#### 覆盖率命令
+
+```bash
+# Run tests with coverage
+./gradlew koverHtmlReport
+
+# Verify coverage thresholds
+./gradlew koverVerify
+
+# XML report for CI
+./gradlew koverXmlReport
+
+# View HTML report (use the command for your OS)
+# macOS:   open build/reports/kover/html/index.html
+# Linux:   xdg-open build/reports/kover/html/index.html
+# Windows: start build/reports/kover/html/index.html
+```
+
+#### 覆盖率目标
+
+| 代码类型 | 目标 |
+|-----------|--------|
+| 关键业务逻辑 | 100% |
+| 公共 API | 90%+ |
+| 通用代码 | 80%+ |
+| 生成的 / 配置代码 | 排除 |
+
+### Ktor testApplication 测试
+
+```kotlin
+class ApiRoutesTest : FunSpec({
+    test("GET /users returns list") {
+        testApplication {
+            application {
+                configureRouting()
+                configureSerialization()
+            }
+
+            val response = client.get("/users")
+
+            response.status shouldBe HttpStatusCode.OK
+            val users = response.body<List<UserResponse>>()
+            users.shouldNotBeEmpty()
+        }
+    }
+
+    test("POST /users creates user") {
+        testApplication {
+            application {
+                configureRouting()
+                configureSerialization()
+            }
+
+            val response = client.post("/users") {
+                contentType(ContentType.Application.Json)
+                setBody(CreateUserRequest("Alice", "alice@example.com"))
+            }
+
+            response.status shouldBe HttpStatusCode.Created
+        }
+    }
+})
+```
+
+### 测试命令
+
+```bash
+# Run all tests
+./gradlew test
+
+# Run specific test class
+./gradlew test --tests "com.example.UserServiceTest"
+
+# Run specific test
+./gradlew test --tests "com.example.UserServiceTest.getUser returns user when found"
+
+# Run with verbose output
+./gradlew test --info
+
+# Run with coverage
+./gradlew koverHtmlReport
+
+# Run detekt (static analysis)
+./gradlew detekt
+
+# Run ktlint (formatting check)
+./gradlew ktlintCheck
+
+# Continuous testing
+./gradlew test --continuous
+```
+
+### 最佳实践
+
+**应做：**
+
+* 先写测试（TDD）
+* 在整个项目中一致地使用 Kotest 的规范样式
+* 对挂起函数使用 MockK 的 `coEvery`/`coVerify`
+* 对协程测试使用 `runTest`
+* 测试行为，而非实现
+* 对纯函数使用基于属性的测试
+* 为清晰起见使用 `data class` 测试固件
+
+**不应做：**
+
+* 混合使用测试框架（选择 Kotest 并坚持使用）
+* 模拟数据类（使用真实实例）
+* 在协程测试中使用 `Thread.sleep()`（改用 `advanceTimeBy`）
+* 跳过 TDD 中的红色阶段
+* 直接测试私有函数
+* 忽略不稳定的测试
+
+### 与 CI/CD 集成
+
+```yaml
+# GitHub Actions example
+test:
+  runs-on: ubuntu-latest
+  steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-java@v4
+      with:
+        distribution: 'temurin'
+        java-version: '21'
+
+    - name: Run tests with coverage
+      run: ./gradlew test koverXmlReport
+
+    - name: Verify coverage
+      run: ./gradlew koverVerify
+
+    - name: Upload coverage
+      uses: codecov/codecov-action@v5
+      with:
+        files: build/reports/kover/report.xml
+        token: ${{ secrets.CODECOV_TOKEN }}
+```
+
+**记住**：测试就是文档。它们展示了你的 Kotlin 代码应如何使用。使用 Kotest 富有表现力的匹配器使测试可读，并使用 MockK 来清晰地模拟依赖项。