Support parallel execution of IDEA tests

compiler/tests-common/tests/org/jetbrains/kotlin/test/JUnit3RunnerWithInners.java

@@ -31,6 +31,11 @@ import java.lang.reflect.Modifier;
  * Works differently for Gradle and JPS. Default is Gradle for now.
  */
 public class JUnit3RunnerWithInners extends Runner implements Filterable, Sortable {
+
+    static {
+        KotlinTestUtils.setIdeaSystemPathProperties();
+    }
+
     private final Runner delegateRunner;
 
     public JUnit3RunnerWithInners(Class<?> klass) {

compiler/tests-common/tests/org/jetbrains/kotlin/test/KotlinTestUtils.java

@@ -90,6 +90,8 @@ import java.util.*;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import static com.intellij.openapi.application.PathManager.PROPERTY_CONFIG_PATH;
+import static com.intellij.openapi.application.PathManager.PROPERTY_SYSTEM_PATH;
 import static org.jetbrains.kotlin.test.InTextDirectivesUtils.*;
 
 public class KotlinTestUtils {
@@ -112,6 +114,19 @@ public class KotlinTestUtils {
 
     private static final List<File> filesToDelete = new ArrayList<>();
 
+    // It's important that this is not created per test, but rather per process.
+    public static final String IDEA_SYSTEM_PATH;
+
+    static {
+        try {
+            IDEA_SYSTEM_PATH = tmpDirForReusableLibrary("idea-system").getPath();
+        }
+        catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+
     /**
      * Syntax:
      *
@@ -1294,4 +1309,9 @@ public class KotlinTestUtils {
         // Several extension if name contains another dot
         return name.indexOf('.', firstDotIndex + 1) != -1;
     }
+
+    public static void setIdeaSystemPathProperties() {
+        System.setProperty(PROPERTY_SYSTEM_PATH, IDEA_SYSTEM_PATH);
+        System.setProperty(PROPERTY_CONFIG_PATH, IDEA_SYSTEM_PATH + "/config");
+    }
 }

idea/build.gradle.kts

@@ -1,3 +1,7 @@
+tasks.withType<Test> {
+    maxParallelForks = Math.max(Runtime.getRuntime().availableProcessors() / 2, 1)
+}
+
 plugins {
     kotlin("jvm")
     id("jps-compatible")