Fixes #1855 and #939: improve error message when the inline mock maker cannot be used.

src/main/java/org/mockito/internal/configuration/InjectingAnnotationEngine.java

@@ -58,7 +58,7 @@ private List<AutoCloseable> processInjectMocks(
         List<AutoCloseable> closeables = new ArrayList<>();
         Class<?> classContext = clazz;
         while (classContext != Object.class) {
-            closeables.add(injectMocks(testInstance));
+            closeables.add(injectCloseableMocks(testInstance));
             classContext = classContext.getSuperclass();
         }
         return closeables;
@@ -79,6 +79,20 @@ private List<AutoCloseable> processIndependentAnnotations(
         return closeables;
     }
 
+    /**
+     * Required by PowerMockito and retained to avoid API breakage despite being internal API.
+     *
+     * @deprecated Use {@link InjectingAnnotationEngine#injectCloseableMocks(Object)}.
+     */
+    @Deprecated
+    public void injectMocks(Object testClassInstance) {
+        try {
+            injectCloseableMocks(testClassInstance).close();
+        } catch (Exception e) {
+            throw new IllegalStateException(e);
+        }
+    }
+
     /**
      * Initializes mock/spies dependencies for objects annotated with
      * &#064;InjectMocks for given testClassInstance.
@@ -88,7 +102,7 @@ private List<AutoCloseable> processIndependentAnnotations(
      * @param testClassInstance
      *            Test class, usually <code>this</code>
      */
-    private AutoCloseable injectMocks(final Object testClassInstance) {
+    private AutoCloseable injectCloseableMocks(final Object testClassInstance) {
         Class<?> clazz = testClassInstance.getClass();
         Set<Field> mockDependentFields = new HashSet<Field>();
         Set<Object> mocks = newMockSafeHashSet();

src/main/java/org/mockito/internal/creation/bytebuddy/InlineByteBuddyMockMaker.java

@@ -4,24 +4,20 @@
  */
 package org.mockito.internal.creation.bytebuddy;
 
-import static org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator.EXCLUDES;
-import static org.mockito.internal.util.StringUtil.join;
-
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.lang.instrument.Instrumentation;
 import java.lang.reflect.Modifier;
+import java.util.Arrays;
 import java.util.Map;
 import java.util.WeakHashMap;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
 import java.util.jar.JarOutputStream;
 
-import javax.tools.ToolProvider;
-
 import net.bytebuddy.agent.ByteBuddyAgent;
 import org.mockito.Incubating;
 import org.mockito.creation.instance.Instantiator;
@@ -35,6 +31,9 @@
 import org.mockito.mock.MockCreationSettings;
 import org.mockito.plugins.InlineMockMaker;
 
+import static org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator.*;
+import static org.mockito.internal.util.StringUtil.*;
+
 /**
  * Agent and subclass based mock maker.
  * <p>
@@ -191,12 +190,34 @@ public class InlineByteBuddyMockMaker implements ClassCreatingMockMaker, InlineM
 
     public InlineByteBuddyMockMaker() {
         if (INITIALIZATION_ERROR != null) {
+            String detail;
+            if (System.getProperty("java.specification.vendor", "")
+                    .toLowerCase()
+                    .contains("android")) {
+                detail =
+                        "It appears as if you are trying to run this mock maker on Android which does not support the instrumentation API.";
+            } else {
+                try {
+                    if (Class.forName("javax.tools.ToolProvider")
+                                    .getMethod("getSystemJavaCompiler")
+                                    .invoke(null)
+                            == null) {
+                        detail =
+                                "It appears as if you are running on a JRE. Either install a JDK or add JNA to the class path.";
+                    } else {
+                        detail =
+                                "It appears as if your JDK does not supply a working agent attachment mechanism.";
+                    }
+                } catch (Throwable ignored) {
+                    detail =
+                            "It appears as if you are running an incomplete JVM installation that might not support all tooling APIs";
+                }
+            }
             throw new MockitoInitializationException(
                     join(
-                            "Could not initialize inline Byte Buddy mock maker. (This mock maker is not supported on Android.)",
-                            ToolProvider.getSystemJavaCompiler() == null
-                                    ? "Are you running a JRE instead of a JDK? The inline mock maker needs to be run on a JDK.\n"
-                                    : "",
+                            "Could not initialize inline Byte Buddy mock maker.",
+                            "",
+                            detail,
                             Platform.describe()),
                     INITIALIZATION_ERROR);
         }
@@ -384,11 +405,12 @@ public <T> StaticMockControl<T> createStaticMock(
                             + "to avoid infinitive loops within Mockito's implementation of static mock handling");
         } else if (type == Thread.class
                 || type == System.class
+                || type == Arrays.class
                 || ClassLoader.class.isAssignableFrom(type)) {
             throw new MockitoException(
                     "It is not possible to mock static methods of "
                             + type.getTypeName()
-                            + "to avoid interfering with the class loading mechanism");
+                            + " to avoid interfering with class loading what leads to infinite loops");
         }
 
         bytecodeGenerator.mockClassStatic(type);