Enable code coverage collection

build.gradle.kts

@@ -1,3 +1,4 @@
+import kotlinx.kover.gradle.plugin.dsl.MetricType
 import kotlinx.validation.build.mavenCentralMetadata
 import kotlinx.validation.build.mavenRepositoryPublishing
 import kotlinx.validation.build.signPublicationIfKeyPresent
@@ -14,6 +15,7 @@ plugins {
     `maven-publish`
     `jvm-test-suite`
     id("org.jetbrains.kotlinx.binary-compatibility-validator")
+    alias(libs.plugins.kover)
 }
 
 group = "org.jetbrains.kotlinx"
@@ -107,6 +109,7 @@ tasks.compileTestKotlin {
 tasks.withType<Test>().configureEach {
     systemProperty("overwrite.output", System.getProperty("overwrite.output", "false"))
     systemProperty("testCasesClassesDirs", sourceSets.test.get().output.classesDirs.asPath)
+    systemProperty("kover.enabled", project.findProperty("kover.enabled")?.toString().toBoolean())
     jvmArgs("-ea")
 }
 
@@ -195,3 +198,25 @@ testing {
 tasks.withType<Sign>().configureEach {
     onlyIf("only sign if signatory is present") { signatory?.keyId != null }
 }
+
+kover {
+    koverReport {
+        filters {
+            excludes {
+                packages("kotlinx.validation.test")
+            }
+        }
+        verify {
+            rule {
+                minBound(80, MetricType.BRANCH)
+                minBound(90, MetricType.LINE)
+            }
+        }
+    }
+    // Unfortunately, we can't test both configuration cache use and the test coverage
+    // simultaneously, so the coverage collection should be enabled explicitly (and that
+    // will disable configuration cache).
+    if (!project.findProperty("kover.enabled")?.toString().toBoolean()) {
+        disable()
+    }
+}

gradle/libs.versions.toml

@@ -39,3 +39,7 @@ gradlePlugin-pluginPublishing = { module = "com.gradle.publish:plugin-publish-pl
 gradlePlugin-kotlin = { module = "org.jetbrains.kotlin:kotlin-gradle-plugin", version.ref = "kotlin" }
 gradlePlugin-android = { module = "com.android.tools.build:gradle", version.ref = "androidGradlePlugin" }
 ## endregion
+
+[plugins]
+
+kover = { id = "org.jetbrains.kotlinx.kover", version = "0.7.5" }

src/functionalTest/kotlin/kotlinx/validation/api/TestDsl.kt

@@ -12,6 +12,8 @@ import org.intellij.lang.annotations.Language
 
 public val API_DIR: String = ApiValidationExtension().apiDumpDirectory
 
+private val koverEnabled: Boolean = System.getProperty("kover.enabled").toBoolean()
+
 internal fun BaseKotlinGradleTest.test(
     gradleVersion: String = "8.5",
     injectPluginClasspath: Boolean = true,
@@ -38,14 +40,19 @@ internal fun BaseKotlinGradleTest.test(
         .withPluginClasspath()
         .withArguments(baseKotlinScope.runner.arguments)
         .withGradleVersion(gradleVersion)
+
+    if (koverEnabled) {
+        // In debug mode, tests will be running inside the same JVM.
+        // That will allow collection coverage info by the Kover.
+        runner.withDebug(true)
+    }
+
     if (injectPluginClasspath) {
         // The hack dating back to https://docs.gradle.org/6.0/userguide/test_kit.html#sub:test-kit-classpath-injection
         // Currently, some tests won't work without it because some classes are missing on the classpath.
         runner.addPluginTestRuntimeClasspath()
     }
     return runner
-    // disabled because of: https://github.com/gradle/gradle/issues/6862
-    // .withDebug(baseKotlinScope.runner.debug)
 }
 
 /**
@@ -165,7 +172,13 @@ internal class AppendableScope(val filePath: String) {
 }
 
 internal class Runner {
-    val arguments: MutableList<String> = mutableListOf("--configuration-cache")
+    val arguments: MutableList<String> = mutableListOf<String>().apply {
+        if (!koverEnabled) {
+            // Configuration cache is incompatible with javaagents being enabled for Gradle
+            // See https://github.com/gradle/gradle/issues/25979
+            add("--configuration-cache")
+        }
+    }
 }
 
 internal fun readFileList(@Language("file-reference") fileName: String): String {

src/functionalTest/kotlin/kotlinx/validation/test/MixedMarkersTest.kt

@@ -31,7 +31,7 @@ class MixedMarkersTest : BaseKotlinGradleTest() {
             }
         }
 
-        runner.withDebug(true).build().apply {
+        runner.build().apply {
             assertTaskSuccess(":apiCheck")
         }
     }

src/functionalTest/kotlin/kotlinx/validation/test/PublicMarkersTest.kt

@@ -41,7 +41,7 @@ class PublicMarkersTest : BaseKotlinGradleTest() {
             }
         }
 
-        runner.withDebug(true).build().apply {
+        runner.build().apply {
             assertTaskSuccess(":apiCheck")
         }
     }