First step of test interceptors (#165)

* First step of test interceptors

This is like JUnit 4 @rules.

This is a lot of code but still incomplete. Some work
still outstanding

 * Inheritance
 * JUnit 5 API testing
 * JUnit 4 API testing
 * Defensive code if there's already an intercept() function

But this is already too big, so lets start here.

* Spotless

* apiDump, more tests

* Early, optimistic, inheritance

* More tests

* Use declaration order

* Rename TestInterceptor.Test to TestFunction

* Simplify BurstKotlinPluginTest

* Promote more tests to TestInterceptorKotlinPluginTest

* apiDump

---------

Co-authored-by: Jesse Wilson <jwilson@squareup.com>

Author: swankjesse

burst-gradle-plugin/src/test/kotlin/app/cash/burst/gradle/GradleTester.kt

@@ -18,6 +18,7 @@ package app.cash.burst.gradle
 import assertk.assertThat
 import assertk.assertions.isIn
 import java.io.File
+import org.gradle.testkit.runner.BuildTask
 import org.gradle.testkit.runner.GradleRunner
 import org.gradle.testkit.runner.TaskOutcome
 
@@ -45,6 +46,11 @@ class GradleTester(
     }
   }
 
+  fun cleanAndBuildAndFail(taskName: String): BuildTask {
+    val result = createRunner("clean", taskName).buildAndFail()
+    return result.task(taskName)!!
+  }
+
   fun readTestSuite(
     className: String,
     testTaskName: String = "test",

burst-gradle-plugin/src/test/kotlin/app/cash/burst/gradle/TestInterceptorGradlePluginTest.kt

@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2025 Cash App
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package app.cash.burst.gradle
+
+import assertk.assertThat
+import assertk.assertions.contains
+import assertk.assertions.isEqualTo
+import assertk.assertions.isNotNull
+import assertk.assertions.isNull
+import org.gradle.testkit.runner.TaskOutcome
+import org.junit.BeforeClass
+import org.junit.Test
+
+class TestInterceptorGradlePluginTest {
+  companion object {
+    private val tester = GradleTester("interceptor")
+
+    @BeforeClass
+    @JvmStatic
+    fun beforeClass() {
+      val result = tester.cleanAndBuildAndFail(":lib:test")
+      assertThat(result.outcome).isEqualTo(TaskOutcome.FAILED)
+    }
+  }
+
+  @Test
+  fun happyPath() {
+    with(tester.readTestSuite("app.cash.burst.tests.BasicTest")) {
+      assertThat(testCases.single().failureMessage).isNull()
+      assertThat(systemOut).isEqualTo(
+        """
+        |intercepting
+        |  packageName=app.cash.burst.tests
+        |  className=BasicTest
+        |  functionName=passingTest
+        |set up
+        |running
+        |tear down
+        |intercepted
+        |
+        """.trimMargin(),
+      )
+    }
+  }
+
+  @Test
+  fun failingTest() {
+    with(tester.readTestSuite("app.cash.burst.tests.FailingTest")) {
+      assertThat(testCases.single().failureMessage).isNotNull().contains("boom!")
+      assertThat(systemOut).isEqualTo(
+        """
+        |set up
+        |tear down
+        |re-throwing exception: boom!
+        |
+        """.trimMargin(),
+      )
+    }
+  }
+
+  /**
+   * Note that this is different from JUnit 4, where rules enclose superclass' @Before functions.
+   */
+  @Test
+  fun beforeTestInSuperclass() {
+    with(tester.readTestSuite("app.cash.burst.tests.BeforeTestInSuperclassTest${'$'}CircleTest")) {
+      assertThat(testCases.single().failureMessage).isNull()
+      assertThat(systemOut).isEqualTo(
+        """
+        |beforeTest
+        |intercepting
+        |running
+        |intercepted
+        |
+        """.trimMargin(),
+      )
+    }
+  }
+
+  /**
+   * Note that this is different from JUnit 4, where rules enclose superclass' @After functions.
+   */
+  @Test
+  fun afterTestInSuperclass() {
+    with(tester.readTestSuite("app.cash.burst.tests.AfterTestInSuperclassTest${'$'}CircleTest")) {
+      assertThat(testCases.single().failureMessage).isNull()
+      assertThat(systemOut).isEqualTo(
+        """
+        |intercepting
+        |running
+        |intercepted
+        |afterTest
+        |
+        """.trimMargin(),
+      )
+    }
+  }
+}

burst-gradle-plugin/src/test/kotlin/app/cash/burst/gradle/junitXml.kt

@@ -47,16 +47,23 @@ internal fun Element.toTestSuite(): TestSuite {
 
 internal fun Element.toTestCase(): TestCase {
   var skipped = false
+  var failureMessage: String? = null
   for (i in 0 until childNodes.length) {
     val item = childNodes.item(i)
-    if (item is Element && item.tagName == "skipped") {
-      skipped = true
+    if (item is Element) {
+      if (item.tagName == "skipped") {
+        skipped = true
+      }
+      if (item.tagName == "failure") {
+        failureMessage = item.getAttribute("message")
+      }
     }
   }
 
   return TestCase(
     name = getAttribute("name"),
     skipped = skipped,
+    failureMessage = failureMessage,
   )
 }
 
@@ -69,4 +76,5 @@ class TestSuite(
 class TestCase(
   val name: String,
   val skipped: Boolean,
+  val failureMessage: String?,
 )

burst-gradle-plugin/src/test/projects/interceptor/build.gradle.kts

@@ -0,0 +1,37 @@
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinJvmCompile
+
+buildscript {
+  repositories {
+    maven {
+      url = file("$rootDir/../../../../../build/testMaven").toURI()
+    }
+    mavenCentral()
+    google()
+  }
+  dependencies {
+    classpath("app.cash.burst:burst-gradle-plugin:${project.property("burstVersion")}")
+    classpath(libs.kotlin.gradlePlugin)
+  }
+}
+
+allprojects {
+  repositories {
+    maven {
+      url = file("$rootDir/../../../../../build/testMaven").toURI()
+    }
+    mavenCentral()
+    google()
+  }
+
+  tasks.withType(JavaCompile::class.java).configureEach {
+    sourceCompatibility = "1.8"
+    targetCompatibility = "1.8"
+  }
+
+  tasks.withType(KotlinJvmCompile::class.java).configureEach {
+    compilerOptions {
+      jvmTarget.set(JvmTarget.JVM_1_8)
+    }
+  }
+}

burst-gradle-plugin/src/test/projects/interceptor/lib/build.gradle.kts

@@ -0,0 +1,8 @@
+plugins {
+  kotlin("jvm")
+  id("app.cash.burst")
+}
+
+dependencies {
+  testImplementation(kotlin("test"))
+}

burst-gradle-plugin/src/test/projects/interceptor/lib/src/test/kotlin/app/cash/burst/tests/AfterTestInSuperclassTest.kt

@@ -0,0 +1,34 @@
+package app.cash.burst.tests
+
+import app.cash.burst.InterceptTest
+import app.cash.burst.TestFunction
+import app.cash.burst.TestInterceptor
+import kotlin.test.AfterTest
+import kotlin.test.Test
+
+class AfterTestInSuperclassTest {
+  open class ShapeTest {
+    @AfterTest
+    fun afterTest() {
+      println("afterTest")
+    }
+  }
+
+  class CircleTest : ShapeTest() {
+    @InterceptTest
+    val interceptor = LoggingInterceptor()
+
+    @Test
+    fun passingTest() {
+      println("running")
+    }
+  }
+
+  class LoggingInterceptor : TestInterceptor {
+    override fun intercept(testFunction: TestFunction) {
+      println("intercepting")
+      testFunction()
+      println("intercepted")
+    }
+  }
+}

burst-gradle-plugin/src/test/projects/interceptor/lib/src/test/kotlin/app/cash/burst/tests/BasicTest.kt

@@ -0,0 +1,39 @@
+package app.cash.burst.tests
+
+import app.cash.burst.InterceptTest
+import app.cash.burst.TestFunction
+import app.cash.burst.TestInterceptor
+import kotlin.test.AfterTest
+import kotlin.test.BeforeTest
+import kotlin.test.Test
+
+class BasicTest {
+  @InterceptTest
+  val interceptor = BasicInterceptor()
+
+  @BeforeTest
+  fun setUp() {
+    println("set up")
+  }
+
+  @AfterTest
+  fun tearDown() {
+    println("tear down")
+  }
+
+  @Test
+  fun passingTest() {
+    println("running")
+  }
+
+  class BasicInterceptor : TestInterceptor {
+    override fun intercept(testFunction: TestFunction) {
+      println("intercepting")
+      println("  packageName=${testFunction.packageName}")
+      println("  className=${testFunction.className}")
+      println("  functionName=${testFunction.functionName}")
+      testFunction()
+      println("intercepted")
+    }
+  }
+}

burst-gradle-plugin/src/test/projects/interceptor/lib/src/test/kotlin/app/cash/burst/tests/BeforeTestInSuperclassTest.kt

@@ -0,0 +1,34 @@
+package app.cash.burst.tests
+
+import app.cash.burst.InterceptTest
+import app.cash.burst.TestFunction
+import app.cash.burst.TestInterceptor
+import kotlin.test.BeforeTest
+import kotlin.test.Test
+
+class BeforeTestInSuperclassTest {
+  open class ShapeTest {
+    @BeforeTest
+    fun beforeTest() {
+      println("beforeTest")
+    }
+  }
+
+  class CircleTest : ShapeTest() {
+    @InterceptTest
+    val interceptor = LoggingInterceptor()
+
+    @Test
+    fun passingTest() {
+      println("running")
+    }
+  }
+
+  class LoggingInterceptor : TestInterceptor {
+    override fun intercept(testFunction: TestFunction) {
+      println("intercepting")
+      testFunction()
+      println("intercepted")
+    }
+  }
+}

burst-gradle-plugin/src/test/projects/interceptor/lib/src/test/kotlin/app/cash/burst/tests/FailingTest.kt

@@ -0,0 +1,39 @@
+package app.cash.burst.tests
+
+import app.cash.burst.InterceptTest
+import app.cash.burst.TestFunction
+import app.cash.burst.TestInterceptor
+import kotlin.test.AfterTest
+import kotlin.test.BeforeTest
+import kotlin.test.Test
+
+class FailingTest {
+  @InterceptTest
+  val interceptor = CatchingInterceptor()
+
+  @BeforeTest
+  fun setUp() {
+    println("set up")
+  }
+
+  @AfterTest
+  fun tearDown() {
+    println("tear down")
+  }
+
+  @Test
+  fun failingTest() {
+    error("boom!")
+  }
+
+  class CatchingInterceptor : TestInterceptor {
+    override fun intercept(testFunction: TestFunction) {
+      try {
+        testFunction()
+      } catch (e: Throwable) {
+        println("re-throwing exception: ${e.message}")
+        throw e
+      }
+    }
+  }
+}

burst-gradle-plugin/src/test/projects/interceptor/settings.gradle.kts

@@ -0,0 +1,9 @@
+dependencyResolutionManagement {
+  versionCatalogs {
+    create("libs") {
+      from(files("../../../../../gradle/libs.versions.toml"))
+    }
+  }
+}
+
+include(":lib")