[Build] Fail the build if `parallel = true` was set for JUnit5 test task
diff --git a/compiler/tests-java8/build.gradle.kts b/compiler/tests-java8/build.gradle.kts
index fd932f1..3a966ac 100644
--- a/compiler/tests-java8/build.gradle.kts
+++ b/compiler/tests-java8/build.gradle.kts
@@ -47,7 +47,6 @@
     withThirdPartyJava8Annotations()
 
     testTask(
-        parallel = true,
         defineJDKEnvVariables = listOf(JdkMajorVersion.JDK_21_0),
         jUnitMode = JUnitMode.JUnit5
     ) {
diff --git a/libraries/scripting/jsr223-test/build.gradle.kts b/libraries/scripting/jsr223-test/build.gradle.kts
index 02f66de..faf5668 100644
--- a/libraries/scripting/jsr223-test/build.gradle.kts
+++ b/libraries/scripting/jsr223-test/build.gradle.kts
@@ -59,7 +59,7 @@
         configureProperties(testRuntimeProvider, testCompilationClasspathProvider)
     }
 
-    testTask("embeddableTest", jUnitMode = JUnitMode.JUnit5, parallel = true, skipInLocalBuild = false) {
+    testTask("embeddableTest", jUnitMode = JUnitMode.JUnit5, skipInLocalBuild = false) {
         workingDir = rootDir
         dependsOn(embeddableTestRuntime)
         classpath = embeddableTestRuntime
diff --git a/libraries/scripting/jvm-host-test/build.gradle.kts b/libraries/scripting/jvm-host-test/build.gradle.kts
index 9b72b96..c1a2d80 100644
--- a/libraries/scripting/jvm-host-test/build.gradle.kts
+++ b/libraries/scripting/jvm-host-test/build.gradle.kts
@@ -46,7 +46,7 @@
     //    classpath = embeddableTestRuntime
     //}
 
-    testTask(taskName = "testWithK1", parallel = true, jUnitMode = JUnitMode.JUnit5, skipInLocalBuild = false) {
+    testTask(taskName = "testWithK1", jUnitMode = JUnitMode.JUnit5, skipInLocalBuild = false) {
         dependsOn(":dist")
         workingDir = rootDir
         doFirst {
diff --git a/repo/gradle-build-conventions/project-tests-convention/src/main/kotlin/ProjectTestsExtension.kt b/repo/gradle-build-conventions/project-tests-convention/src/main/kotlin/ProjectTestsExtension.kt
index 0eafd6a..8b6b678 100644
--- a/repo/gradle-build-conventions/project-tests-convention/src/main/kotlin/ProjectTestsExtension.kt
+++ b/repo/gradle-build-conventions/project-tests-convention/src/main/kotlin/ProjectTestsExtension.kt
@@ -3,6 +3,7 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
+import org.gradle.api.GradleException
 import org.gradle.api.Project
 import org.gradle.api.Task
 import org.gradle.api.artifacts.Configuration
@@ -15,7 +16,6 @@
 import org.gradle.api.provider.ListProperty
 import org.gradle.api.provider.Property
 import org.gradle.api.tasks.JavaExec
-import org.gradle.api.tasks.SourceSet
 import org.gradle.api.tasks.TaskProvider
 import org.gradle.api.tasks.testing.Test
 import org.gradle.kotlin.dsl.dependencies
@@ -201,7 +201,7 @@
             return project.tasks.register(taskName)
         }
         if (jUnitMode == JUnitMode.JUnit5 && parallel != null) {
-            project.logger.error("JUnit5 tests are parallel by default and its configured with `junit-platform.properties`, please remove `parallel=$parallel` argument")
+            throw GradleException("JUnit5 tests are parallel by default and its configured with `junit-platform.properties`, please remove `parallel=$parallel` argument")
         }
         return project.createGeneralTestTask(
             taskName,