Add test tasks to the Gradle model built for MPP

Add `testTasks` to KotlinTarget model class, build them
based on task names until proper test runs API is available.

idea/kotlin-gradle-tooling/src/KotlinMPPGradleModel.kt

@@ -140,6 +140,7 @@ interface KotlinTarget : Serializable {
     val disambiguationClassifier: String?
     val platform: KotlinPlatform
     val compilations: Collection<KotlinCompilation>
+    val testTasks: Collection<KotlinTestTask>
     val jar: KotlinTargetJar?
 
     companion object {
@@ -147,6 +148,10 @@ interface KotlinTarget : Serializable {
     }
 }
 
+interface KotlinTestTask : Serializable {
+    val taskName: String
+}
+
 interface ExtraFeatures : Serializable {
     val coroutinesState: String?
     val isHMPPEnabled: Boolean

idea/kotlin-gradle-tooling/src/KotlinMPPGradleModelBuilder.kt

@@ -5,10 +5,7 @@
 
 package org.jetbrains.kotlin.gradle
 
-import org.gradle.api.Named
+import org.gradle.api.*
-import org.gradle.api.NamedDomainObjectContainer
-import org.gradle.api.Project
-import org.gradle.api.Task
 import org.gradle.api.artifacts.Configuration
 import org.gradle.api.artifacts.Dependency
 import org.gradle.api.artifacts.component.ProjectComponentIdentifier
@@ -249,7 +246,8 @@ class KotlinMPPGradleModelBuilder : ModelBuilderService {
             buildCompilation(it, disambiguationClassifier, sourceSetMap, dependencyResolver, project, dependencyMapper)
         }
         val jar = buildTargetJar(gradleTarget, project)
-        val target = KotlinTargetImpl(gradleTarget.name, targetPresetName, disambiguationClassifier, platform, compilations, jar)
+        val testTasks = buildTestTasks(project, gradleTarget)
+        val target = KotlinTargetImpl(gradleTarget.name, targetPresetName, disambiguationClassifier, platform, compilations, testTasks, jar)
         compilations.forEach {
             it.disambiguationClassifier = target.disambiguationClassifier
             it.platform = target.platform
@@ -257,6 +255,38 @@ class KotlinMPPGradleModelBuilder : ModelBuilderService {
         return target
     }
 
+    private fun buildTestTasks(project: Project, gradleTarget: Named): Collection<KotlinTestTask> {
+        // TODO: use the test runs API to extract the test tasks once it is available
+
+        // Otherwise, find the Kotlin test task with names matching the target name. This is a workaround that makes assumptions about
+        // the tasks naming logic and is therefore an unstable and temporary solution until test runs API is implemented:
+        @Suppress("UNCHECKED_CAST")
+        val kotlinTestTaskClass = try {
+            gradleTarget.javaClass.classLoader.loadClass("org.jetbrains.kotlin.gradle.tasks.KotlinTest") as Class<out Task>
+        } catch (_: ClassNotFoundException) {
+            return emptyList()
+        }
+
+        val targetDisambiguationClassifier = run {
+            val getDisambiguationClassifier = gradleTarget.javaClass.getMethodOrNull("getDisambiguationClassifier")
+                ?: return emptyList()
+
+            getDisambiguationClassifier(gradleTarget) as String?
+        }
+
+        // The 'targetName' of a test task matches the target disambiguation classifier, potentially with suffix, e.g. jsBrowser
+        val getTargetName = kotlinTestTaskClass.getDeclaredMethodOrNull("getTargetName") ?: return emptyList()
+
+        return project.tasks.filter { kotlinTestTaskClass.isInstance(it) }.mapNotNull { task ->
+            val testTaskDisambiguationClassifier = getTargetName(task) as String?
+            task.name.takeIf {
+                targetDisambiguationClassifier.isNullOrEmpty() ||
+                        testTaskDisambiguationClassifier != null &&
+                        testTaskDisambiguationClassifier.startsWith(targetDisambiguationClassifier.orEmpty())
+            }
+        }.map(::KotlinTestTaskImpl)
+    }
+
     private fun buildTargetJar(gradleTarget: Named, project: Project): KotlinTargetJar? {
         val targetClass = gradleTarget.javaClass
         val getArtifactsTaskName = targetClass.getMethodOrNull("getArtifactsTaskName") ?: return null

idea/kotlin-gradle-tooling/src/KotlinMPPGradleModelImpl.kt

@@ -132,6 +132,7 @@ data class KotlinTargetImpl(
     override val disambiguationClassifier: String?,
     override val platform: KotlinPlatform,
     override val compilations: Collection<KotlinCompilation>,
+    override val testTasks: Collection<KotlinTestTask>,
     override val jar: KotlinTargetJar?
 ) : KotlinTarget {
     override fun toString() = name
@@ -146,10 +147,19 @@ data class KotlinTargetImpl(
                 cloningCache[initialCompilation] = it
             }
         }.toList(),
+        target.testTasks.map { initialTestTask ->
+            (cloningCache[initialTestTask] as? KotlinTestTask) ?: KotlinTestTaskImpl(initialTestTask.taskName).also {
+                cloningCache[initialTestTask] = it
+            }
+        },
         KotlinTargetJarImpl(target.jar?.archiveFile)
     )
 }
 
+data class KotlinTestTaskImpl(
+    override val taskName: String
+) : KotlinTestTask
+
 data class ExtraFeaturesImpl(
     override val coroutinesState: String?,
     override val isHMPPEnabled: Boolean