Use spearate testkit dir for each run (elastic#42013)

Gradle Testkit reuses the teskit dir by default between tests.
With this change we use a temporary one for each run
hoping it will fix elastic#41431

buildSrc/src/test/java/org/elasticsearch/gradle/ExportElasticsearchBuildResourcesTaskIT.java

@@ -21,44 +21,35 @@
 
 import org.elasticsearch.gradle.test.GradleIntegrationTestCase;
 import org.gradle.testkit.runner.BuildResult;
-import org.gradle.testkit.runner.GradleRunner;
 
 
 public class ExportElasticsearchBuildResourcesTaskIT extends GradleIntegrationTestCase {
 
     public static final String PROJECT_NAME = "elasticsearch-build-resources";
 
     public void testUpToDateWithSourcesConfigured() {
-        GradleRunner.create()
-            .withProjectDir(getProjectDir(PROJECT_NAME))
+        getGradleRunner(PROJECT_NAME)
             .withArguments("clean", "-s")
-            .withPluginClasspath()
             .build();
 
-        BuildResult result = GradleRunner.create()
-            .withProjectDir(getProjectDir(PROJECT_NAME))
+        BuildResult result = getGradleRunner(PROJECT_NAME)
             .withArguments("buildResources", "-s", "-i")
-            .withPluginClasspath()
             .build();
         assertTaskSuccessful(result, ":buildResources");
         assertBuildFileExists(result, PROJECT_NAME, "build-tools-exported/checkstyle.xml");
         assertBuildFileExists(result, PROJECT_NAME, "build-tools-exported/checkstyle_suppressions.xml");
 
-        result = GradleRunner.create()
-            .withProjectDir(getProjectDir(PROJECT_NAME))
+        result = getGradleRunner(PROJECT_NAME)
             .withArguments("buildResources", "-s", "-i")
-            .withPluginClasspath()
             .build();
         assertTaskUpToDate(result, ":buildResources");
         assertBuildFileExists(result, PROJECT_NAME, "build-tools-exported/checkstyle.xml");
         assertBuildFileExists(result, PROJECT_NAME, "build-tools-exported/checkstyle_suppressions.xml");
     }
 
     public void testImplicitTaskDependencyCopy() {
-        BuildResult result = GradleRunner.create()
-            .withProjectDir(getProjectDir(PROJECT_NAME))
+        BuildResult result = getGradleRunner(PROJECT_NAME)
             .withArguments("clean", "sampleCopyAll", "-s", "-i")
-            .withPluginClasspath()
             .build();
 
         assertTaskSuccessful(result, ":buildResources");
@@ -69,10 +60,8 @@ public void testImplicitTaskDependencyCopy() {
     }
 
     public void testImplicitTaskDependencyInputFileOfOther() {
-        BuildResult result = GradleRunner.create()
-            .withProjectDir(getProjectDir(PROJECT_NAME))
+        BuildResult result = getGradleRunner(PROJECT_NAME)
             .withArguments("clean", "sample", "-s", "-i")
-            .withPluginClasspath()
             .build();
 
         assertTaskSuccessful(result, ":sample");
@@ -81,11 +70,12 @@ public void testImplicitTaskDependencyInputFileOfOther() {
     }
 
     public void testIncorrectUsage() {
-        BuildResult result = GradleRunner.create()
-            .withProjectDir(getProjectDir(PROJECT_NAME))
-            .withArguments("noConfigAfterExecution", "-s", "-i")
-            .withPluginClasspath()
-            .buildAndFail();
-        assertOutputContains("buildResources can't be configured after the task ran");
+        assertOutputContains(
+            getGradleRunner(PROJECT_NAME)
+                .withArguments("noConfigAfterExecution", "-s", "-i")
+                .buildAndFail()
+                .getOutput(),
+            "buildResources can't be configured after the task ran"
+        );
     }
 }

buildSrc/src/test/java/org/elasticsearch/gradle/precommit/JarHellTaskIT.java

@@ -2,7 +2,6 @@
 
 import org.elasticsearch.gradle.test.GradleIntegrationTestCase;
 import org.gradle.testkit.runner.BuildResult;
-import org.gradle.testkit.runner.GradleRunner;
 
 /*
  * Licensed to Elasticsearch under one or more contributor
@@ -25,10 +24,8 @@
 public class JarHellTaskIT extends GradleIntegrationTestCase {
 
     public void testJarHellDetected() {
-        BuildResult result = GradleRunner.create()
-            .withProjectDir(getProjectDir("jarHell"))
+        BuildResult result = getGradleRunner("jarHell")
             .withArguments("clean", "precommit", "-s", "-Dlocal.repo.path=" + getLocalTestRepoPath())
-            .withPluginClasspath()
             .buildAndFail();
 
         assertTaskFailed(result, ":jarHell");

buildSrc/src/test/java/org/elasticsearch/gradle/test/GradleIntegrationTestCase.java

@@ -4,8 +4,12 @@
 import org.gradle.testkit.runner.BuildTask;
 import org.gradle.testkit.runner.GradleRunner;
 import org.gradle.testkit.runner.TaskOutcome;
+import org.junit.Rule;
+import org.junit.rules.TemporaryFolder;
 
 import java.io.File;
+import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.List;
@@ -16,6 +20,9 @@
 
 public abstract class GradleIntegrationTestCase extends GradleUnitTestCase {
 
+    @Rule
+    public TemporaryFolder testkitTmpDir = new TemporaryFolder();
+
     protected File getProjectDir(String name) {
         File root = new File("src/testKit/");
         if (root.exists() == false) {
@@ -26,9 +33,16 @@ protected File getProjectDir(String name) {
     }
 
     protected GradleRunner getGradleRunner(String sampleProject) {
+        File testkit;
+        try {
+            testkit = testkitTmpDir.newFolder();
+        } catch (IOException e) {
+            throw new UncheckedIOException(e);
+        }
         return GradleRunner.create()
             .withProjectDir(getProjectDir(sampleProject))
-            .withPluginClasspath();
+            .withPluginClasspath()
+            .withTestKitDir(testkit);
     }
 
     protected File getBuildDir(String name) {

buildSrc/src/test/java/org/elasticsearch/gradle/testclusters/TestClustersPluginIT.java

@@ -21,12 +21,21 @@
 import org.elasticsearch.gradle.test.GradleIntegrationTestCase;
 import org.gradle.testkit.runner.BuildResult;
 import org.gradle.testkit.runner.GradleRunner;
+import org.junit.Before;
 import org.junit.Ignore;
 
+
 import java.util.Arrays;
 
 public class TestClustersPluginIT extends GradleIntegrationTestCase {
 
+    private GradleRunner runner;
+
+    @Before
+    public void setUp() throws Exception {
+        runner = getGradleRunner("testclusters");
+    }
+
     public void testListClusters() {
         BuildResult result = getTestClustersRunner("listTestClusters").build();
 
@@ -190,10 +199,7 @@ private GradleRunner getTestClustersRunner(String... tasks) {
         arguments[tasks.length] = "-s";
         arguments[tasks.length + 1] = "-i";
         arguments[tasks.length + 2] = "-Dlocal.repo.path=" + getLocalTestRepoPath();
-        return GradleRunner.create()
-            .withProjectDir(getProjectDir("testclusters"))
-            .withArguments(arguments)
-            .withPluginClasspath();
+        return runner.withArguments(arguments);
     }
 
     private void assertStartedAndStoppedOnce(BuildResult result, String nodeName) {