From dda761ffc2fc85cac5729e3973e53583243682d5 Mon Sep 17 00:00:00 2001
From: Sebastian Sdorra <sebastian.sdorra@cloudogu.com>
Date: Fri, 18 Dec 2020 14:23:36 +0100
Subject: [PATCH] Fix unit tests on Java 11 (#1483)

The unit test I18nServlet and MultiParentClassLoaderTest are failing on Java 11.
This is because they mock ClassLoaders which cause a jvm error.

The following tickets describe the problem in more detail:

- https://bugs.openjdk.java.net/browse/JDK-8254969
- https://github.com/mockito/mockito/issues/2043
- https://github.com/mockito/mockito/issues/1696
---
 Jenkinsfile                                   |   2 +-
 build/Dockerfile                              |   2 +-
 build/Makefile                                |   2 +-
 pom.xml                                       |   2 +-
 .../java/sonia/scm/web/i18n/I18nServlet.java  |   1 -
 .../plugin/MultiParentClassLoaderTest.java    | 195 +++++------
 .../sonia/scm/web/i18n/I18nServletTest.java   | 308 ++++++++++--------
 7 files changed, 282 insertions(+), 230 deletions(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index 362fc1ea6a..9acca06822 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -204,7 +204,7 @@ String developmentBranch
 String mainBranch
 
 Maven setupMavenBuild() {
-  MavenWrapperInDocker mvn = new MavenWrapperInDocker(this, "scmmanager/java-build:8u275-b01")
+  MavenWrapperInDocker mvn = new MavenWrapperInDocker(this, "scmmanager/java-build:11.0.9_11.1")
   mvn.enableDockerHost = true
 
   // disable logging durring the build
diff --git a/build/Dockerfile b/build/Dockerfile
index ab9b395cc6..b5b2585c2b 100644
--- a/build/Dockerfile
+++ b/build/Dockerfile
@@ -22,7 +22,7 @@
 # SOFTWARE.
 #
 
-FROM adoptopenjdk/openjdk8:x86_64-debian-jdk8u275-b01
+FROM adoptopenjdk/openjdk11:x86_64-debian-jdk-11.0.9_11.1
 
 ENV DOCKER_VERSION=19.03.8 \
     DOCKER_CHANNEL=stable \
diff --git a/build/Makefile b/build/Makefile
index 58c2d7cd19..8aa8cefc1d 100644
--- a/build/Makefile
+++ b/build/Makefile
@@ -1,4 +1,4 @@
-VERSION:=8u275-b01
+VERSION:=11.0.9_11.1
 
 .PHONY:build
 build:
diff --git a/pom.xml b/pom.xml
index 796888372f..9e1fcdd0dd 100644
--- a/pom.xml
+++ b/pom.xml
@@ -608,7 +608,7 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-surefire-plugin</artifactId>
-        <version>2.22.0</version>
+        <version>3.0.0-M5</version>
         <configuration>
           <!--
           skips surefire tests without skipping failsafe tests.
diff --git a/scm-webapp/src/main/java/sonia/scm/web/i18n/I18nServlet.java b/scm-webapp/src/main/java/sonia/scm/web/i18n/I18nServlet.java
index 11ec8b5978..3c7f1cfef5 100644
--- a/scm-webapp/src/main/java/sonia/scm/web/i18n/I18nServlet.java
+++ b/scm-webapp/src/main/java/sonia/scm/web/i18n/I18nServlet.java
@@ -138,7 +138,6 @@ public class I18nServlet extends HttpServlet {
     return context.getStage() == Stage.PRODUCTION;
   }
 
-  @VisibleForTesting
   private Optional<JsonNode> collectJsonFile(String path) throws IOException {
     LOG.debug("Collect plugin translations from path {} for every plugin", path);
     JsonNode mergedJsonNode = null;
diff --git a/scm-webapp/src/test/java/sonia/scm/plugin/MultiParentClassLoaderTest.java b/scm-webapp/src/test/java/sonia/scm/plugin/MultiParentClassLoaderTest.java
index f28fbe71a6..55e7e4b1b2 100644
--- a/scm-webapp/src/test/java/sonia/scm/plugin/MultiParentClassLoaderTest.java
+++ b/scm-webapp/src/test/java/sonia/scm/plugin/MultiParentClassLoaderTest.java
@@ -21,114 +21,125 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
-    
+
 package sonia.scm.plugin;
 
+import com.google.common.io.Resources;
+import net.bytebuddy.ByteBuddy;
+import net.bytebuddy.implementation.FixedValue;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
 import java.io.IOException;
+import java.net.MalformedURLException;
 import java.net.URL;
-import java.util.Arrays;
-import java.util.Collections;
+import java.net.URLClassLoader;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.List;
-import static org.junit.Assert.*;
-import org.junit.Before;
-import org.junit.Rule;
-import org.junit.Test;
-import org.junit.rules.TemporaryFolder;
-import org.junit.runner.RunWith;
-import org.mockito.Mock;
-import static org.mockito.Mockito.*;
-import static org.hamcrest.Matchers.*;
-import org.mockito.invocation.InvocationOnMock;
-import org.mockito.junit.MockitoJUnitRunner;
-import org.mockito.stubbing.Answer;
+
+import static net.bytebuddy.matcher.ElementMatchers.named;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 /**
  *
  * @author Sebastian Sdorra
  */
-@RunWith(MockitoJUnitRunner.class)
-public class MultiParentClassLoaderTest
-{
-  
-  @Mock
-  private ClassLoader parent1;
-  
-  @Mock
-  private ClassLoader parent2;
+class MultiParentClassLoaderTest {
 
-  private MultiParentClassLoader classLoader;
-  
-  @Before
-  public void setUp(){
-     classLoader = new MultiParentClassLoader(parent1, parent2);
-  }
-  
-  @SuppressWarnings("unchecked")
-  @Test(expected = ClassNotFoundException.class)
-  public void testClassNotFoundException() throws ClassNotFoundException
-  {
-    when(parent1.loadClass("string")).thenThrow(ClassNotFoundException.class);
-    when(parent2.loadClass("string")).thenThrow(ClassNotFoundException.class);
-    classLoader.loadClass("string");
-  }
-  
-  @Rule
-  public TemporaryFolder tempFolder = new TemporaryFolder();
-  
   @Test
-  public void testGetResource() throws IOException
-  {
-    URL url1 = tempFolder.newFile().toURI().toURL();
-    URL url2 = tempFolder.newFile().toURI().toURL();
-    when(parent1.getResource("resource1")).thenReturn(url1);
-    when(parent2.getResource("resource2")).thenReturn(url2);
-    
-    assertEquals(url1, classLoader.getResource("resource1"));
-    assertEquals(url2, classLoader.getResource("resource2"));
-    assertNull(classLoader.getResource("resource3"));
-  }
-  
-  @Test
-  public void testGetResources() throws IOException{
-        URL url1 = tempFolder.newFile().toURI().toURL();
-    URL url2 = tempFolder.newFile().toURI().toURL();
-    URL url3 = tempFolder.newFile().toURI().toURL();
-    when(parent1.getResources("resources")).thenReturn(res(url1, url2));
-    when(parent2.getResources("resources")).thenReturn(res(url3));
-    
-    List<URL> enm = Collections.list(classLoader.getResources("resources"));
-    assertThat(enm, containsInAnyOrder(url1, url2, url3));
-  }
-  
-  @Test
-  public void testLoadClass() throws ClassNotFoundException{
-    when(parent1.loadClass("string")).then(new ClassAnswer(String.class));
-    when(parent1.loadClass("int")).then(new ClassAnswer(Integer.class));
-    
-    assertEquals(String.class, classLoader.loadClass("string"));
-    assertEquals(Integer.class, classLoader.loadClass("int"));
-  }
-  private static class ClassAnswer implements Answer<Object> {
-  
-    private final Class<?> clazz;
+  void shouldLoadClass(@TempDir Path directory) throws IOException, ClassNotFoundException, IllegalAccessException, InstantiationException {
+    byte[] classOneRaw = createDynamicClass("One", "Value of one");
+    ClassLoader one = createClassLoader(directory, "One.class", classOneRaw);
+    byte[] classTwoRaw = createDynamicClass("Two", "Value of two");
+    ClassLoader two = createClassLoader(directory, "Two.class", classTwoRaw);
 
-    public ClassAnswer(
-      Class<?> clazz)
-    {
-      this.clazz = clazz;
+    MultiParentClassLoader classLoader = new MultiParentClassLoader(one, two);
+    assertClassToString(classLoader, "One", "Value of one");
+    assertClassToString(classLoader, "Two", "Value of two");
+  }
+
+  private void assertClassToString(ClassLoader classLoader, String className, String toStringValue) throws ClassNotFoundException, IllegalAccessException, InstantiationException {
+    Class<?> aClass = classLoader.loadClass(className);
+    assertThat(aClass.newInstance()).hasToString(toStringValue);
+  }
+
+  private byte[] createDynamicClass(String name, String toStringValue) {
+    return new ByteBuddy()
+      .subclass(Object.class)
+      .name(name)
+      .method(named("toString"))
+      .intercept(FixedValue.value(toStringValue))
+      .make()
+      .getBytes();
+  }
+
+  @Test
+  void shouldThrowClassNotFoundException(@TempDir Path directory) throws MalformedURLException {
+    URLClassLoader one = createClassLoader(directory.resolve("one"));
+    URLClassLoader two = createClassLoader(directory.resolve("two"));
+    MultiParentClassLoader classLoader = new MultiParentClassLoader(one, two);
+    assertThrows(ClassNotFoundException.class, () -> classLoader.loadClass("UnknownClass"));
+  }
+
+  @Test
+  void shouldReturnResource(@TempDir Path directory) throws IOException {
+    URLClassLoader one = createClassLoader(directory.resolve("one"), "one", "one");
+    URLClassLoader two = createClassLoader(directory.resolve("two"), "two", "two");
+    MultiParentClassLoader classLoader = new MultiParentClassLoader(one, two);
+
+    assertResource(classLoader, "one", "one");
+    assertResource(classLoader, "two", "two");
+  }
+
+  @Test
+  void shouldReturnResources(@TempDir Path directory) throws IOException {
+    URLClassLoader one = createClassLoader(directory.resolve("one"), "both", "one");
+    URLClassLoader two = createClassLoader(directory.resolve("two"), "both", "two");
+    MultiParentClassLoader classLoader = new MultiParentClassLoader(one, two);
+
+    Enumeration<URL> both = classLoader.getResources("both");
+    List<String> content = toStrings(both);
+
+    assertThat(content).containsOnly("one", "two");
+  }
+
+  @SuppressWarnings("UnstableApiUsage")
+  private List<String> toStrings(Enumeration<URL> urlEnumeration) throws IOException {
+    List<String> content = new ArrayList<>();
+    while (urlEnumeration.hasMoreElements()) {
+      URL url = urlEnumeration.nextElement();
+      content.add(Resources.toString(url, StandardCharsets.UTF_8));
     }
+    return content;
+  }
 
-    @Override
-    public Object answer(InvocationOnMock invocation) throws Throwable
-    {
-      return clazz;
-    }
-  
+  @SuppressWarnings("UnstableApiUsage")
+  private void assertResource(ClassLoader classLoader, String resource, String content) throws IOException {
+    URL url = classLoader.getResource(resource);
+    assertThat(url).isNotNull();
+    String urlContent = Resources.toString(url, StandardCharsets.UTF_8);
+    assertThat(urlContent).isEqualTo(content);
   }
-  
-  private Enumeration<URL> res(URL... urls){
-    return Collections.enumeration(Arrays.asList(urls));
+
+  private URLClassLoader createClassLoader(Path directory, String resource, String content) throws IOException {
+    return createClassLoader(directory, resource, content.getBytes(StandardCharsets.UTF_8));
   }
-  
+
+  private URLClassLoader createClassLoader(Path directory, String resource, byte[] content) throws IOException {
+    Path file = directory.resolve(resource);
+    Files.createDirectories(file.getParent());
+    Files.write(file, content);
+    return createClassLoader(directory);
+  }
+
+  private URLClassLoader createClassLoader(Path directory) throws MalformedURLException {
+    ClassLoader parent = ClassLoader.getSystemClassLoader().getParent();
+    return new URLClassLoader(new URL[]{directory.toUri().toURL()}, parent);
+  }
+
 }
diff --git a/scm-webapp/src/test/java/sonia/scm/web/i18n/I18nServletTest.java b/scm-webapp/src/test/java/sonia/scm/web/i18n/I18nServletTest.java
index 1a189926bc..978d45fbd9 100644
--- a/scm-webapp/src/test/java/sonia/scm/web/i18n/I18nServletTest.java
+++ b/scm-webapp/src/test/java/sonia/scm/web/i18n/I18nServletTest.java
@@ -29,6 +29,7 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 import com.github.legman.EventBus;
 import org.apache.commons.lang3.StringUtils;
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.api.io.TempDir;
@@ -41,19 +42,23 @@ import sonia.scm.cache.CacheManager;
 import sonia.scm.lifecycle.RestartEventFactory;
 import sonia.scm.plugin.PluginLoader;
 
+import javax.annotation.Nonnull;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.PrintWriter;
+import java.net.MalformedURLException;
 import java.net.URL;
+import java.net.URLClassLoader;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
-import java.util.Enumeration;
+import java.util.Collection;
+import java.util.List;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.fail;
@@ -96,8 +101,12 @@ class I18nServletTest {
     "}"
   );
 
+  private static final String[] ALL_PLUGIN_JSON = new String[]{
+    GIT_PLUGIN_JSON, HG_PLUGIN_JSON, SVN_PLUGIN_JSON
+  };
+
   private static String json(String... parts) {
-    return String.join("\n", parts ).replaceAll("'", "\"");
+    return String.join("\n", parts).replaceAll("'", "\"");
   }
 
   @Mock
@@ -106,142 +115,12 @@ class I18nServletTest {
   @Mock
   private PluginLoader pluginLoader;
 
-  @Mock
-  private ClassLoader classLoader;
-
   @Mock
   private CacheManager cacheManager;
 
   @Mock
   private Cache<String, JsonNode> cache;
 
-  private I18nServlet servlet;
-
-
-  @BeforeEach
-  void init() {
-    when(pluginLoader.getUberClassLoader()).thenReturn(classLoader);
-    when(cacheManager.<String, JsonNode>getCache(I18nServlet.CACHE_NAME)).thenReturn(cache);
-    servlet = new I18nServlet(context, pluginLoader, cacheManager);
-  }
-
-  @Test
-  void shouldCleanCacheOnRestartEvent() {
-    EventBus eventBus = new EventBus("forTestingOnly");
-    eventBus.register(servlet);
-    eventBus.post(RestartEventFactory.create(I18nServlet.class, "Restart to reload the plugin resources"));
-
-    verify(cache).clear();
-  }
-
-  @Test
-  void shouldFailWith404OnMissingResources() throws IOException {
-    String path = "/locales/de/plugins.json";
-    HttpServletRequest request = mock(HttpServletRequest.class);
-    HttpServletResponse response = mock(HttpServletResponse.class);
-    when(request.getServletPath()).thenReturn(path);
-    when(classLoader.getResources("locales/de/plugins.json")).thenReturn(
-      I18nServlet.class.getClassLoader().getResources("something/not/available")
-    );
-
-    servlet.doGet(request, response);
-
-    verify(response).setStatus(404);
-  }
-
-  @Test
-  void shouldFailWith500OnIOException() throws IOException {
-    stage(Stage.DEVELOPMENT);
-    HttpServletRequest request = mock(HttpServletRequest.class);
-    when(request.getServletPath()).thenReturn("/locales/de/plugins.json");
-    HttpServletResponse response = mock(HttpServletResponse.class);
-    when(classLoader.getResources("locales/de/plugins.json")).thenThrow(new IOException("failed"));
-
-    servlet.doGet(request, response);
-
-    verify(response).setStatus(500);
-  }
-
-  private void stage(Stage stage) {
-    when(context.getStage()).thenReturn(stage);
-  }
-
-  @Test
-  void inDevelopmentStageShouldNotUseCache(@TempDir Path temp) throws IOException {
-    stage(Stage.DEVELOPMENT);
-    mockResources(temp, "locales/de/plugins.json");
-    HttpServletRequest request = mock(HttpServletRequest.class);
-    when(request.getServletPath()).thenReturn("/locales/de/plugins.json");
-
-    HttpServletResponse response = mock(HttpServletResponse.class);
-    String json = doGetString(request, response);
-
-    assertJson(json);
-    verify(cache, never()).get(any());
-  }
-
-  private String doGetString(HttpServletRequest request, HttpServletResponse response) throws IOException {
-    ByteArrayOutputStream baos = new ByteArrayOutputStream();
-    PrintWriter writer = new PrintWriter(baos);
-    when(response.getWriter()).thenReturn(writer);
-
-    servlet.doGet(request, response);
-
-    writer.flush();
-    return baos.toString(StandardCharsets.UTF_8.name());
-  }
-
-  private void mockResources(Path directory, String resourcePath) throws IOException {
-    Enumeration<URL> resources = Collections.enumeration(
-      Arrays.asList(
-        toURL(directory, "git.json", GIT_PLUGIN_JSON),
-        toURL(directory, "hg.json", HG_PLUGIN_JSON),
-        toURL(directory, "svn.json", SVN_PLUGIN_JSON)
-      )
-    );
-    when(classLoader.getResources(resourcePath)).thenReturn(resources);
-  }
-
-  private URL toURL(Path directory, String name, String content) throws IOException {
-    Path file = directory.resolve(name);
-    java.nio.file.Files.write(file, content.getBytes(StandardCharsets.UTF_8));
-    return file.toUri().toURL();
-  }
-
-  @Test
-  void shouldGetFromCacheInProductionStage() throws IOException {
-    String path = "/locales/de/plugins.json";
-    stage(Stage.PRODUCTION);
-    HttpServletRequest request = mock(HttpServletRequest.class);
-    when(request.getServletPath()).thenReturn(path);
-    HttpServletResponse response = mock(HttpServletResponse.class);
-
-    ObjectMapper mapper = new ObjectMapper();
-    JsonNode jsonNode = mapper.readTree(GIT_PLUGIN_JSON);
-    when(cache.get(path)).thenReturn(jsonNode);
-
-    String json = doGetString(request, response);
-    assertThat(json).contains("scm-git-plugin").doesNotContain("scm-hg-plugin");
-    verifyHeaders(response);
-  }
-
-  @Test
-  void shouldStoreToCacheInProductionStage(@TempDir Path temp) throws IOException {
-    String path = "/locales/de/plugins.json";
-    mockResources(temp, "locales/de/plugins.json");
-    stage(Stage.PRODUCTION);
-    HttpServletRequest request = mock(HttpServletRequest.class);
-    when(request.getServletPath()).thenReturn(path);
-    HttpServletResponse response = mock(HttpServletResponse.class);
-
-    String json = doGetString(request, response);
-
-    verify(cache).put(any(String.class), any(JsonNode.class));
-
-    verifyHeaders(response);
-    assertJson(json);
-  }
-
   @Test
   void shouldNotHaveInvalidPluginsJsonFiles() throws IOException {
     String path = getClass().getClassLoader().getResource("locales/en/plugins.json").getPath();
@@ -266,6 +145,169 @@ class I18nServletTest {
     }
   }
 
+  @Nested
+  class WithCacheManager {
+
+    @BeforeEach
+    void init() {
+      when(cacheManager.<String, JsonNode>getCache(I18nServlet.CACHE_NAME)).thenReturn(cache);
+    }
+
+    @Test
+    void shouldFailWith404OnMissingResources(@TempDir Path directory) throws IOException {
+      String path = "/locales/de/plugins.json";
+      HttpServletRequest request = mock(HttpServletRequest.class);
+      when(request.getServletPath()).thenReturn(path);
+      HttpServletResponse response = mock(HttpServletResponse.class);
+
+      mockUberClassLoader(directory);
+
+      createServlet().doGet(request, response);
+      verify(response).setStatus(404);
+    }
+
+    private void mockUberClassLoader(Path... directories) throws MalformedURLException {
+      mockUberClassLoader(Arrays.asList(directories));
+    }
+
+    private void mockUberClassLoader(Collection<Path> directories) throws MalformedURLException {
+      List<URL> urls = new ArrayList<>();
+      for (Path directory : directories) {
+        urls.add(directory.toUri().toURL());
+      }
+      ClassLoader bootstrapLoader = ClassLoader.getSystemClassLoader().getParent();
+      URLClassLoader classLoader = new URLClassLoader(urls.toArray(new URL[0]), bootstrapLoader);
+      when(pluginLoader.getUberClassLoader()).thenReturn(classLoader);
+    }
+
+    @Test
+    void shouldFailWith500OnIOException(@TempDir Path directory) throws IOException {
+      stage(Stage.DEVELOPMENT);
+      HttpServletRequest request = mock(HttpServletRequest.class);
+      when(request.getServletPath()).thenReturn("/locales/de/plugins.json");
+      HttpServletResponse response = mock(HttpServletResponse.class);
+
+      mockResource(directory, "locales/de/plugins.json", "invalid json");
+
+      createServlet().doGet(request, response);
+
+      verify(response).setStatus(500);
+    }
+
+    private void mockResource(Path directory, String resourcePath, String content) throws IOException {
+      Path file = directory.resolve(resourcePath);
+      Files.createDirectories(file.getParent());
+      Files.write(file, content.getBytes(StandardCharsets.UTF_8));
+
+      mockUberClassLoader(directory);
+    }
+
+    private void stage(Stage stage) {
+      when(context.getStage()).thenReturn(stage);
+    }
+
+    @Test
+    void inDevelopmentStageShouldNotUseCache(@TempDir Path temp) throws IOException {
+      stage(Stage.DEVELOPMENT);
+      mockResources(temp, "locales/de/plugins.json");
+      HttpServletRequest request = mock(HttpServletRequest.class);
+      when(request.getServletPath()).thenReturn("/locales/de/plugins.json");
+      HttpServletResponse response = mock(HttpServletResponse.class);
+
+      I18nServlet servlet = createServlet();
+      String json = doGetString(servlet, request, response);
+
+      assertJson(json);
+      verify(cache, never()).get(any());
+    }
+
+    @Nonnull
+    private I18nServlet createServlet() {
+      return new I18nServlet(context, pluginLoader, cacheManager);
+    }
+
+    private String doGetString(I18nServlet servlet, HttpServletRequest request, HttpServletResponse response) throws IOException {
+      ByteArrayOutputStream baos = new ByteArrayOutputStream();
+      PrintWriter writer = new PrintWriter(baos);
+      when(response.getWriter()).thenReturn(writer);
+
+      servlet.doGet(request, response);
+
+      writer.flush();
+      return baos.toString(StandardCharsets.UTF_8.name());
+    }
+
+    private void mockResources(Path directory, String resourcePath) throws IOException {
+      List<Path> directories = new ArrayList<>();
+      for (int i = 0; i < ALL_PLUGIN_JSON.length; i++) {
+        Path pluginDirectory = directory.resolve("plugin-" + i);
+        Path file = pluginDirectory.resolve(resourcePath);
+        Files.createDirectories(file.getParent());
+        Files.write(file, ALL_PLUGIN_JSON[i].getBytes(StandardCharsets.UTF_8));
+        directories.add(pluginDirectory);
+      }
+      mockUberClassLoader(directories);
+    }
+
+    @Test
+    void shouldGetFromCacheInProductionStage() throws IOException {
+      String path = "/locales/de/plugins.json";
+      stage(Stage.PRODUCTION);
+      HttpServletRequest request = mock(HttpServletRequest.class);
+      when(request.getServletPath()).thenReturn(path);
+      HttpServletResponse response = mock(HttpServletResponse.class);
+
+      ObjectMapper mapper = new ObjectMapper();
+      JsonNode jsonNode = mapper.readTree(GIT_PLUGIN_JSON);
+      when(cache.get(path)).thenReturn(jsonNode);
+
+      I18nServlet servlet = createServlet();
+      String json = doGetString(servlet, request, response);
+      assertThat(json).contains("scm-git-plugin").doesNotContain("scm-hg-plugin");
+      verifyHeaders(response);
+    }
+
+    @Test
+    void shouldStoreToCacheInProductionStage(@TempDir Path temp) throws IOException {
+      String path = "/locales/de/plugins.json";
+      mockResources(temp, "locales/de/plugins.json");
+      stage(Stage.PRODUCTION);
+      HttpServletRequest request = mock(HttpServletRequest.class);
+      when(request.getServletPath()).thenReturn(path);
+      HttpServletResponse response = mock(HttpServletResponse.class);
+
+      I18nServlet servlet = createServlet();
+      String json = doGetString(servlet, request, response);
+
+      verify(cache).put(any(String.class), any(JsonNode.class));
+
+      verifyHeaders(response);
+      assertJson(json);
+    }
+
+
+    @Nested
+    class WithDefaultClassLoader {
+
+      @BeforeEach
+      void init() {
+        when(pluginLoader.getUberClassLoader()).thenReturn(I18nServletTest.class.getClassLoader());
+      }
+
+      @Test
+      void shouldCleanCacheOnRestartEvent() {
+        I18nServlet servlet = createServlet();
+        EventBus eventBus = new EventBus("forTestingOnly");
+        eventBus.register(servlet);
+        eventBus.post(RestartEventFactory.create(I18nServlet.class, "Restart to reload the plugin resources"));
+
+        verify(cache).clear();
+      }
+
+    }
+
+  }
+
   private void verifyHeaders(HttpServletResponse response) {
     verify(response).setCharacterEncoding("UTF-8");
     verify(response).setContentType("application/json");