Provide JenkinsRule.restart() implementation

src/main/java/org/jvnet/hudson/test/JenkinsRule.java

@@ -44,6 +44,7 @@
 import hudson.EnvVars;
 import hudson.Extension;
 import hudson.ExtensionList;
+import hudson.FilePath;
 import hudson.Functions;
 import hudson.Launcher;
 import hudson.Main;
@@ -3281,6 +3282,41 @@ public Description getTestDescription() {
         return testDescription;
     }
 
+    /**
+     * Restart the current instance with the same port and a copy of its {@code JENKINS_HOME}.
+     */
+    public void restart() throws Throwable {
+        // create backup of current instance in new home
+        URL source = jenkins.getRootDir().toURI().toURL();
+        File copy = new TemporaryDirectoryAllocator().allocate();
+
+        if(source.getProtocol().equals("file")) {
+            File src = new File(source.toURI());
+            if (src.isDirectory()) {
+                new FilePath(src).copyRecursiveTo("**/*",new FilePath(copy));
+            } else if (src.getName().endsWith(".zip")) {
+                new FilePath(src).unzip(new FilePath(copy));
+            }
+        } else {
+            File tmp = File.createTempFile("hudson","zip");
+            try {
+                FileUtils.copyURLToFile(source,tmp);
+                new FilePath(tmp).unzip(new FilePath(copy));
+            } finally {
+                FileUtils.deleteQuietly(tmp);
+            }
+        }
+
+        // shutdown and cleanup current instance
+        after();
+
+        // init new instance with backup
+        withExistingHome(copy);
+
+        // startup new instance
+        before();
+    }
+
     private NameValuePair getCrumbHeaderNVP() {
         return new NameValuePair(jenkins.getCrumbIssuer().getDescriptor().getCrumbRequestField(),
                         jenkins.getCrumbIssuer().getCrumb((javax.servlet.ServletRequest) null));

src/test/java/org/jvnet/hudson/test/JenkinsRuleTest.java

@@ -2,6 +2,9 @@
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.not;
+import static org.hamcrest.collection.IsCollectionWithSize.hasSize;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -14,6 +17,7 @@
 import hudson.model.FreeStyleProject;
 import hudson.model.RootAction;
 import hudson.model.User;
+import java.io.File;
 import java.io.IOException;
 import java.net.URL;
 import java.nio.file.Files;
@@ -30,6 +34,7 @@
 import org.htmlunit.util.WebConnectionWrapper;
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.runner.Description;
 import org.kohsuke.stapler.DataBoundConstructor;
 import org.kohsuke.stapler.DataBoundSetter;
 import org.kohsuke.stapler.HttpResponse;
@@ -424,6 +429,31 @@ public void waitForCompletion() throws Exception {
         j.assertBuildStatusSuccess(j.waitForCompletion(b));
     }
 
+    @Test
+    public void restart() throws Throwable {
+        // preserve relevant properties
+        URL previousUrl = j.getURL();
+        Description previousTestDescription = j.testDescription;
+        File previousRoot = j.jenkins.getRootDir();
+
+        // create some configuration
+        j.createFreeStyleProject();
+        assertThat(j.jenkins.getJobNames(), hasSize(1));
+
+        // restart the instance with same port and new JENKINS_HOME
+        j.restart();
+
+        // validate properties and configuration were preserved
+        assertThat(j.getURL(), equalTo(previousUrl));
+        assertThat(j.testDescription, equalTo(previousTestDescription));
+        assertThat(j.jenkins.getRootDir(), not(previousRoot));
+        assertThat(j.jenkins.getJobNames(), hasSize(1));
+
+        // validate restarted instance is working
+        j.createFreeStyleProject();
+        assertThat(j.jenkins.getJobNames(), hasSize(2));
+    }
+
     @Test
     public void mimeType() throws IOException {
         JenkinsRule.WebClient wc = j.createWebClient();
@@ -441,4 +471,5 @@ public WebResponse getResponse(WebRequest request) throws IOException {
         wc.getPage(j.getURL());
         assertEquals("text/javascript", contentType.get());
     }
+
 }

src/test/java/org/jvnet/hudson/test/junit/jupiter/JUnit5JenkinsRuleTest.java

@@ -0,0 +1,45 @@
+package org.jvnet.hudson.test.junit.jupiter;
+
+import org.junit.jupiter.api.Test;
+import org.jvnet.hudson.test.JenkinsRule;
+import org.junit.runner.Description;
+import java.io.File;
+import java.net.URL;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.not;
+import static org.hamcrest.collection.IsCollectionWithSize.hasSize;
+
+/**
+ * Test {@link JUnit5JenkinsRule}.
+ */
+@WithJenkins
+class JUnit5JenkinsRuleTest {
+
+    @Test
+    void restart(JenkinsRule rule) throws Throwable {
+        // preserve relevant properties
+        URL previousUrl = rule.getURL();
+        Description previousTestDescription = rule.getTestDescription();
+        File previousRoot = rule.jenkins.getRootDir();
+
+        // create some configuration
+        rule.createFreeStyleProject();
+        assertThat(rule.jenkins.getJobNames(), hasSize(1));
+
+        // restart the instance with same port and new JENKINS_HOME
+        rule.restart();
+
+        // validate properties and configuration were preserved
+        assertThat(rule.getURL(), equalTo(previousUrl));
+        assertThat(rule.getTestDescription(), equalTo(previousTestDescription));
+        assertThat(rule.jenkins.getRootDir(), not(previousRoot));
+        assertThat(rule.jenkins.getJobNames(), hasSize(1));
+
+        // validate restarted instance is working
+        rule.createFreeStyleProject();
+        assertThat(rule.jenkins.getJobNames(), hasSize(2));
+    }
+
+}

src/test/java/org/jvnet/hudson/test/junit/jupiter/JenkinsRuleResolverTest.java

@@ -3,6 +3,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.collection.IsCollectionWithSize.hasSize;
 import static org.hamcrest.collection.IsEmptyCollection.empty;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 
 import java.io.IOException;
 import org.junit.jupiter.api.Test;
@@ -17,4 +18,9 @@ void jenkinsRuleIsAccessible(JenkinsRule rule) throws IOException {
         rule.createFreeStyleProject("job-0");
         assertThat(rule.jenkins.getJobNames(), hasSize(1));
     }
+
+    @Test
+    void instanceOf(JenkinsRule rule) {
+        assertInstanceOf(JUnit5JenkinsRule.class, rule);
+    }
 }

src/test/java/org/jvnet/hudson/test/junit/jupiter/JenkinsRuleResolverWithMethodScopeTest.java

@@ -3,6 +3,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.collection.IsCollectionWithSize.hasSize;
 import static org.hamcrest.collection.IsEmptyCollection.empty;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 
 import java.io.IOException;
 import org.junit.jupiter.api.Test;
@@ -17,4 +18,10 @@ void jenkinsRuleIsAccessible(JenkinsRule rule) throws IOException {
         rule.createFreeStyleProject("job-0");
         assertThat(rule.jenkins.getJobNames(), hasSize(1));
     }
+
+    @Test
+    @WithJenkins
+    void instanceOf(JenkinsRule rule) {
+        assertInstanceOf(JUnit5JenkinsRule.class, rule);
+    }
 }