Android: Mock ModuleInstaller in tests

- Split ModuleInstaller to ModuleInstallerImpl and its interface.
- Remove //components/module_installer/../src-test
- Create a new ModuleInstallerRule to use in tests.
- Update bytecode rewriting to use getInstance().
- Remove dependency on arcore in chrome_test_java (used on Kitkat).

Bug: 981084
Change-Id: I7909fe67fa29bdb0e5c787faf4293600283421ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1687303
Commit-Queue: Peter Wen <wnwen@chromium.org>
Reviewed-by: Eric Stevenson <estevenson@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676623}

build/android/bytecode/java/org/chromium/bytecode/ByteCodeProcessor.java

@@ -113,15 +113,20 @@ class ByteCodeProcessor {
             writer = new ClassWriter(reader, 0);
         }
         ClassVisitor chain = writer;
-        /* DEBUGGING:
-         To see the bytecode for a specific class:
-           if (entry.getName().contains("YourClassName")) {
-             chain = new TraceClassVisitor(chain, new PrintWriter(System.out));
-           }
+        /* DEBUGGING:}
          To see objectweb.asm code that will generate bytecode for a given class:
-           java -cp "third_party/ow2_asm/lib/asm-5.0.1.jar:third_party/ow2_asm/lib/"\
-               "asm-util-5.0.1.jar:out/Debug/lib.java/jar_containing_yourclass.jar" \
-               org.objectweb.asm.util.ASMifier org.package.YourClassName
+
+         java -cp
+         "third_party/ow2_asm/lib/asm.jar:third_party/ow2_asm/lib/asm-util.jar:out/Debug/lib.java/jar_containing_yourclass.jar"
+         org.objectweb.asm.util.ASMifier org.package.YourClassName
+
+         See this pdf for more details: https://asm.ow2.io/asm4-guide.pdf
+
+         To see the bytecode for a specific class, uncomment this code with your class name:
+
+        if (entry.getName().contains("YOUR_CLASS_NAME")) {
+          chain = new TraceClassVisitor(chain, new PrintWriter(System.out));
+        }
         */
         if (sShouldUseThreadAnnotations) {
             chain = new ThreadAssertionClassAdapter(chain);

build/android/bytecode/java/org/chromium/bytecode/SplitCompatClassAdapter.java

@@ -6,6 +6,7 @@ package org.chromium.bytecode;
 
 import static org.objectweb.asm.Opcodes.ACC_PROTECTED;
 import static org.objectweb.asm.Opcodes.ALOAD;
+import static org.objectweb.asm.Opcodes.INVOKEINTERFACE;
 import static org.objectweb.asm.Opcodes.INVOKESPECIAL;
 import static org.objectweb.asm.Opcodes.INVOKESTATIC;
 import static org.objectweb.asm.Opcodes.RETURN;
@@ -34,6 +35,9 @@ class SplitCompatClassAdapter extends ClassVisitor {
 
     private static final String MODULE_INSTALLER_CLASS_NAME =
             "org/chromium/components/module_installer/ModuleInstaller";
+    private static final String GET_INSTANCE_METHOD_NAME = "getInstance";
+    private static final String GET_INSTANCE_DESCRIPTOR =
+            TypeUtils.getMethodDescriptor(MODULE_INSTALLER_CLASS_NAME);
     private static final String INIT_ACTIVITY_METHOD_NAME = "initActivity";
     private static final String INIT_ACTIVITY_DESCRIPTOR =
             TypeUtils.getMethodDescriptor(VOID, CONTEXT);
@@ -107,7 +111,7 @@ class SplitCompatClassAdapter extends ClassVisitor {
      * <pre>
      * protected void attachBaseContext(Context base) {
      *     super.attachBaseContext(base);
-     *     ModuleInstaller.initActivity(this);
+     *     ModuleInstaller.getInstance().initActivity(this);
      * }
      * </pre>
      */
@@ -115,16 +119,30 @@ class SplitCompatClassAdapter extends ClassVisitor {
         MethodVisitor mv = super.visitMethod(ACC_PROTECTED, ATTACH_BASE_CONTEXT_METHOD_NAME,
                 ATTACH_BASE_CONTEXT_DESCRIPTOR, null, null);
         mv.visitCode();
-        mv.visitVarInsn(ALOAD, 0); // load "this" on stack
-        mv.visitVarInsn(ALOAD, 1); // load first method parameter on stack (Context)
+        // Push "this" on stack.
+        mv.visitVarInsn(ALOAD, 0);
+        // Push first method parameter on stack (Context).
+        mv.visitVarInsn(ALOAD, 1);
+        // Pop argument from stack (Context).
+        // Pop target object from stack ("this").
+        // Calls attachBaseContext.
         mv.visitMethodInsn(INVOKESPECIAL, ANDROID_APP_ACTIVITY_CLASS_NAME,
-                ATTACH_BASE_CONTEXT_METHOD_NAME,
-                ATTACH_BASE_CONTEXT_DESCRIPTOR); // invoke super's attach base context
-        mv.visitVarInsn(ALOAD, 0); // load "this" on stack
-        mv.visitMethodInsn(INVOKESTATIC, MODULE_INSTALLER_CLASS_NAME, INIT_ACTIVITY_METHOD_NAME,
-                INIT_ACTIVITY_DESCRIPTOR);
+                ATTACH_BASE_CONTEXT_METHOD_NAME, ATTACH_BASE_CONTEXT_DESCRIPTOR, false);
+        // Push return value on stack (ModuleInstaller).
+        // Calls getInstance.
+        mv.visitMethodInsn(INVOKESTATIC, MODULE_INSTALLER_CLASS_NAME, GET_INSTANCE_METHOD_NAME,
+                GET_INSTANCE_DESCRIPTOR, false);
+        // Push "this" on stack.
+        mv.visitVarInsn(ALOAD, 0);
+        // Pop argument from stack ("this").
+        // Pop target object from stack (ModuleInstaller).
+        // Calls initActivity.
+        mv.visitMethodInsn(INVOKEINTERFACE, MODULE_INSTALLER_CLASS_NAME, INIT_ACTIVITY_METHOD_NAME,
+                INIT_ACTIVITY_DESCRIPTOR, true);
         mv.visitInsn(RETURN);
-        mv.visitMaxs(2, 2); // max stack size - 2, max locals - 2
+        // Max stack size = 2 (Only push at most 2 before popping).
+        // Max locals = 2 ("this" and 1 parameter).
+        mv.visitMaxs(2, 2);
         mv.visitEnd();
     }
 

chrome/android/BUILD.gn

@@ -852,7 +852,6 @@ android_library("chrome_test_java") {
     "//third_party/android_deps:com_android_support_preference_v7_java",
     "//third_party/android_deps:com_android_support_recyclerview_v7_java",
     "//third_party/android_deps:com_android_support_support_annotations_java",
-    "//third_party/android_deps:com_google_ar_core_java",
     "//third_party/android_deps:com_google_protobuf_protobuf_lite_java",
     "//third_party/android_sdk:android_test_base_java",
     "//third_party/android_sdk:android_test_mock_java",
@@ -1039,6 +1038,7 @@ if (enable_vr || enable_arcore) {
             "//third_party/gvr-android-sdk:gvr_common_java",
             ":chrome_test_util_java",
             "//components/module_installer/android:module_installer_java",
+            "//components/module_installer/android:module_installer_stub_java",
             "//components/module_installer/android:module_installer_test_java",
           ]
 

chrome/android/chrome_public_apk_tmpl.gni

@@ -226,9 +226,6 @@ template("chrome_public_common_apk_or_module_tmpl") {
     if (_target_type == "android_app_bundle_module") {
       deps +=
           [ "//components/module_installer/android:module_installer_impl_java" ]
-    } else if (_target_type == "instrumentation_test_apk") {
-      deps +=
-          [ "//components/module_installer/android:module_installer_test_java" ]
     } else {
       deps +=
           [ "//components/module_installer/android:module_installer_stub_java" ]

chrome/android/features/autofill_assistant/public/java/src/org/chromium/chrome/browser/autofill_assistant/AutofillAssistantModuleEntryProvider.java

@@ -27,7 +27,7 @@ public class AutofillAssistantModuleEntryProvider {
     @Nullable
     /* package */ static AutofillAssistantModuleEntry getModuleEntryIfInstalled(Context context) {
         // Required to access resources in DFM using this activity as context.
-        ModuleInstaller.initActivity(context);
+        ModuleInstaller.getInstance().initActivity(context);
         if (AutofillAssistantModule.isInstalled()) {
             return AutofillAssistantModule.getImpl();
         }
@@ -92,11 +92,11 @@ public class AutofillAssistantModuleEntryProvider {
                 });
         // Shows toast informing user about install start.
         ui.showInstallStartUi();
-        ModuleInstaller.install("autofill_assistant", (success) -> {
+        ModuleInstaller.getInstance().install("autofill_assistant", (success) -> {
             if (success) {
                 // Clean install of chrome will have issues here without initializing
                 // after installation of DFM.
-                ModuleInstaller.initActivity(activity);
+                ModuleInstaller.getInstance().initActivity(activity);
                 // Don't show success UI from DFM, transition to autobot UI directly.
                 callback.onResult(AutofillAssistantModule.getImpl());
                 return;

chrome/android/java/src/org/chromium/chrome/browser/ChromeApplication.java

@@ -121,12 +121,12 @@ public class ChromeApplication extends Application {
 
             // Record via UMA all modules that have been requested and are currently installed. This
             // will tell us the install penetration of each module over time.
-            ModuleInstaller.recordModuleAvailability();
+            ModuleInstaller.getInstance().recordModuleAvailability();
         }
 
         // Write installed modules to crash keys. This needs to be done as early as possible so that
         // these values are set before any crashes are reported.
-        ModuleInstaller.updateCrashKeys();
+        ModuleInstaller.getInstance().updateCrashKeys();
 
         BuildInfo.setFirebaseAppId(FirebaseConfig.getFirebaseAppId());
 

chrome/android/java/src/org/chromium/chrome/browser/vr/ArCoreInstallUtils.java

@@ -60,7 +60,7 @@ public class ArCoreInstallUtils implements ModuleInstallUi.FailureUiListener {
     private ArCoreInstallUtils(long nativeArCoreInstallUtils) {
         mNativeArCoreInstallUtils = nativeArCoreInstallUtils;
         // Need to be called before trying to access the AR module.
-        ModuleInstaller.init();
+        ModuleInstaller.getInstance().init();
     }
 
     @Override
@@ -98,7 +98,7 @@ public class ArCoreInstallUtils implements ModuleInstallUi.FailureUiListener {
         mTab = tab;
         ModuleInstallUi ui = new ModuleInstallUi(mTab, R.string.ar_module_title, this);
         ui.showInstallStartUi();
-        ModuleInstaller.install("ar", success -> {
+        ModuleInstaller.getInstance().install("ar", success -> {
             assert shouldRequestInstallArModule() != success;
 
             if (success) {

chrome/android/javatests/src/org/chromium/chrome/browser/vr/VrDaydreamReadyModuleInstallTest.java

@@ -29,12 +29,17 @@ import org.chromium.chrome.browser.vr.util.VrTestRuleUtils;
 import org.chromium.chrome.test.ChromeActivityTestRule;
 import org.chromium.chrome.test.ChromeJUnit4RunnerDelegate;
 import org.chromium.components.module_installer.ModuleInstaller;
+import org.chromium.components.module_installer.ModuleInstallerRule;
 
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.concurrent.Callable;
 
 /**
  * End-to-end tests for installing the VR DFM on Daydream-ready phones on startup.
+ *
+ * TODO(agrieve): This test may be better as a robolectric test.
  */
 @RunWith(ParameterizedRunner.class)
 @UseRunnerDelegate(ChromeJUnit4RunnerDelegate.class)
@@ -48,12 +53,24 @@ public class VrDaydreamReadyModuleInstallTest {
     @Rule
     public RuleChain mRuleChain;
 
+    private ModuleInstallerRule mModuleInstallerRule;
+
     private ChromeActivityTestRule mVrTestRule;
 
+    private final Set<String> mModulesRequestedDeferred = new HashSet<>();
+
     public VrDaydreamReadyModuleInstallTest(Callable<ChromeActivityTestRule> callable)
             throws Exception {
         mVrTestRule = callable.call();
-        mRuleChain = VrTestRuleUtils.wrapRuleInActivityRestrictionRule(mVrTestRule);
+        mModuleInstallerRule = new ModuleInstallerRule(new ModuleInstaller() {
+            @Override
+            public void installDeferred(String moduleName) {
+                mModulesRequestedDeferred.add(moduleName);
+            }
+        });
+        mRuleChain =
+                RuleChain.outerRule(mModuleInstallerRule)
+                        .around(VrTestRuleUtils.wrapRuleInActivityRestrictionRule(mVrTestRule));
     }
 
     /** Tests that the install is requested deferred. */
@@ -62,8 +79,8 @@ public class VrDaydreamReadyModuleInstallTest {
     @XrActivityRestriction({XrActivityRestriction.SupportedActivity.ALL})
     @Restriction({RESTRICTION_TYPE_DEVICE_DAYDREAM})
     @VrModuleNotInstalled
-    public void testDeferredRequestOnStartup() throws InterruptedException {
+    public void testDeferredRequestOnStartup() {
         Assert.assertTrue("VR module should have been deferred installed at startup",
-                ModuleInstaller.didRequestDeferred("vr"));
+                mModulesRequestedDeferred.contains("vr"));
     }
 }

components/module_installer/android/BUILD.gn

@@ -10,11 +10,12 @@ import("//build/config/android/rules.gni")
 # build.
 android_library("module_installer_java") {
   java_files = [
-    "java/src-stub/org/chromium/components/module_installer/ModuleInstaller.java",
+    "java/src-stub/org/chromium/components/module_installer/ModuleInstallerImpl.java",
+    "java/src-common/org/chromium/components/module_installer/ModuleInstaller.java",
     "java/src-common/org/chromium/components/module_installer/OnModuleInstallFinishedListener.java",
     "java/src-common/org/chromium/components/module_installer/Module.java",
   ]
-  jar_excluded_patterns = [ "*/ModuleInstaller.class" ]
+  jar_excluded_patterns = [ "*/ModuleInstallerImpl.class" ]
   deps = [
     "//base:base_java",
   ]
@@ -24,7 +25,7 @@ android_library("module_installer_java") {
 # Contains stub implementation to be used for builds not supporting modules
 # (e.g. APKs).
 android_library("module_installer_stub_java") {
-  java_files = [ "java/src-stub/org/chromium/components/module_installer/ModuleInstaller.java" ]
+  java_files = [ "java/src-stub/org/chromium/components/module_installer/ModuleInstallerImpl.java" ]
   deps = [
     ":module_installer_java",
     "//base:base_java",
@@ -36,7 +37,7 @@ android_library("module_installer_stub_java") {
 # bundles).
 android_library("module_installer_impl_java") {
   java_files = [
-    "java/src-impl/org/chromium/components/module_installer/ModuleInstaller.java",
+    "java/src-impl/org/chromium/components/module_installer/ModuleInstallerImpl.java",
     "java/src-impl/org/chromium/components/module_installer/ModuleInstallerBackend.java",
     "java/src-impl/org/chromium/components/module_installer/FakeModuleInstallerBackend.java",
     "java/src-impl/org/chromium/components/module_installer/PlayCoreModuleInstallerBackend.java",
@@ -50,10 +51,12 @@ android_library("module_installer_impl_java") {
 }
 
 android_library("module_installer_test_java") {
-  java_files = [ "java/src-test/org/chromium/components/module_installer/ModuleInstaller.java" ]
+  testonly = true
+  java_files = [ "javatests/src/org/chromium/components/module_installer/ModuleInstallerRule.java" ]
   deps = [
     ":module_installer_java",
     "//base:base_java",
+    "//third_party/junit",
   ]
   jacoco_never_instrument = true
 }

components/module_installer/android/java/src-common/org/chromium/components/module_installer/Module.java

@@ -56,7 +56,7 @@ public class Module<T> {
         // Accessing classes in the module may cause its DEX file to be loaded. And on some devices
         // that causes a read mode violation.
         try (StrictModeContext ignored = StrictModeContext.allowDiskReads()) {
-            ModuleInstaller.init();
+            ModuleInstaller.getInstance().init();
             Class.forName(mImplClassName);
             return true;
         } catch (ClassNotFoundException e) {
@@ -64,18 +64,18 @@ public class Module<T> {
         }
     }
 
-    /** Requests install of the module. See {@link ModuleInstaller#install} for more details. */
+    /** Requests install of the module. See {@link ModuleInstallerImpl#install} for more details. */
     public void install(OnModuleInstallFinishedListener onFinishedListener) {
         assert !isInstalled();
-        ModuleInstaller.install(mName, onFinishedListener);
+        ModuleInstaller.getInstance().install(mName, onFinishedListener);
     }
 
     /**
-     * Requests deferred install of the module. See {@link ModuleInstaller#installDeferred} for
+     * Requests deferred install of the module. See {@link ModuleInstallerImpl#installDeferred} for
      * more details.
      */
     public void installDeferred() {
-        ModuleInstaller.installDeferred(mName);
+        ModuleInstaller.getInstance().installDeferred(mName);
     }
 
     /**
@@ -85,7 +85,7 @@ public class Module<T> {
     public T getImpl() {
         assert isInstalled();
         if (mImpl == null) {
-            ModuleInstaller.init();
+            ModuleInstaller.getInstance().init();
             // Accessing classes in the module may cause its DEX file to be loaded. And on some
             // devices that causes a read mode violation.
             try (StrictModeContext ignored = StrictModeContext.allowDiskReads()) {

components/module_installer/android/java/src-common/org/chromium/components/module_installer/ModuleInstaller.java

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.components.module_installer;
+
+import android.content.Context;
+
+import org.chromium.base.VisibleForTesting;
+
+/**
+ * This interface contains all the necessary methods to orchestrate the installation of dynamic
+ * feature modules (DFMs).
+ */
+public interface ModuleInstaller {
+    /** Returns the singleton instance from the correct implementation. */
+    static ModuleInstaller getInstance() {
+        return ModuleInstallerImpl.getInstance();
+    }
+
+    @VisibleForTesting
+    static void setInstanceForTesting(ModuleInstaller moduleInstaller) {
+        ModuleInstallerImpl.setInstanceForTesting(moduleInstaller);
+    }
+
+    /** Needs to be called before trying to access a module. */
+    default void init() {}
+
+    /**
+     * Needs to be called in attachBaseContext of the activities that want to have access to
+     * splits prior to application restart.
+     *
+     * For details, see:
+     * https://developer.android.com/reference/com/google/android/play/core/splitcompat/SplitCompat.html#install(android.content.Context)
+     */
+    default void initActivity(Context context) {}
+
+    /**
+     * Records via UMA all modules that have been requested and are currently installed. The intent
+     * is to measure the install penetration of each module.
+     */
+    default void recordModuleAvailability() {}
+
+    /** Writes fully installed and emulated modules to crash keys. */
+    default void updateCrashKeys() {}
+
+    /**
+     * Requests the install of a module. The install will be performed asynchronously.
+     *
+     * @param moduleName Name of the module as defined in GN.
+     * @param onFinishedListener Listener to be called once installation is finished.
+     */
+    default void install(String moduleName, OnModuleInstallFinishedListener onFinishedListener) {}
+
+    /**
+     * Asynchronously installs module in the background when on unmetered connection and charging.
+     * Install is best effort and may fail silently. Upon success, the module will only be available
+     * after Chrome restarts.
+     *
+     * @param moduleName Name of the module.
+     */
+    default void installDeferred(String moduleName) {}
+}

components/module_installer/android/java/src-impl/org/chromium/components/module_installer/ModuleInstaller.java → components/module_installer/android/java/src-impl/org/chromium/components/module_installer/ModuleInstallerImpl.java

@@ -30,53 +30,54 @@ import java.util.Set;
 import java.util.TreeSet;
 
 /** Installs dynamic feature modules (DFMs). */
-public class ModuleInstaller {
+public class ModuleInstallerImpl implements ModuleInstaller {
     /** Command line switch for activating the fake backend.  */
     private static final String FAKE_FEATURE_MODULE_INSTALL = "fake-feature-module-install";
-    private static final Map<String, List<OnModuleInstallFinishedListener>> sModuleNameListenerMap =
+    private static ModuleInstaller sInstance = new ModuleInstallerImpl();
+    private static boolean sAppContextSplitCompatted;
+    private final Map<String, List<OnModuleInstallFinishedListener>> mModuleNameListenerMap =
             new HashMap<>();
-    private static ModuleInstallerBackend sBackend;
-    private static boolean sSplitCompatted;
+    private ModuleInstallerBackend mBackend;
 
-    /** Needs to be called before trying to access a module. */
-    public static void init() {
-        if (sSplitCompatted) return;
+    /** Returns the singleton instance. */
+    public static ModuleInstaller getInstance() {
+        return sInstance;
+    }
+
+    public static void setInstanceForTesting(ModuleInstaller moduleInstaller) {
+        sInstance = moduleInstaller;
+    }
+
+    @Override
+    public void init() {
+        if (sAppContextSplitCompatted) return;
         // SplitCompat.install may copy modules into Chrome's internal folder or clean them up.
         try (StrictModeContext ignored = StrictModeContext.allowDiskWrites()) {
             SplitCompat.install(ContextUtils.getApplicationContext());
-            sSplitCompatted = true;
+            sAppContextSplitCompatted = true;
         }
         // SplitCompat.install may add emulated modules. Thus, update crash keys.
         updateCrashKeys();
     }
 
-    /**
-     * Needs to be called in attachBaseContext of the activities that want to have access to
-     * splits prior to application restart.
-     *
-     * For details, see:
-     * https://developer.android.com/reference/com/google/android/play/core/splitcompat/SplitCompat.html#install(android.content.Context)
-     */
-    public static void initActivity(Context context) {
+    @Override
+    public void initActivity(Context context) {
         SplitCompat.install(context);
     }
 
-    /**
-     * Records via UMA all modules that have been requested and are currently installed. The intent
-     * is to measure the install penetration of each module.
-     */
-    public static void recordModuleAvailability() {
+    @Override
+    public void recordModuleAvailability() {
         if (!CommandLine.getInstance().hasSwitch(FAKE_FEATURE_MODULE_INSTALL)) {
             PlayCoreModuleInstallerBackend.recordModuleAvailability();
         }
     }
 
-    /** Writes fully installed and emulated modules to crash keys. */
-    public static void updateCrashKeys() {
+    @Override
+    public void updateCrashKeys() {
         Context context = ContextUtils.getApplicationContext();
 
         // Get modules that are fully installed as split APKs (excluding base which is always
-        // intalled). Tree set to have ordered and, thus, deterministic results.
+        // installed). Tree set to have ordered and, thus, deterministic results.
         Set<String> fullyInstalledModules = new TreeSet<>();
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
             // Split APKs are only supported on Android L+.
@@ -97,7 +98,7 @@ public class ModuleInstaller {
         // emulation of later modules won't work. If splitcompat has not been called no modules are
         // emulated. Therefore, use an empty set in that case.
         Set<String> emulatedModules = new TreeSet<>();
-        if (sSplitCompatted) {
+        if (sAppContextSplitCompatted) {
             emulatedModules.addAll(
                     SplitInstallManagerFactory.create(context).getInstalledModules());
             emulatedModules.removeAll(fullyInstalledModules);
@@ -109,21 +110,15 @@ public class ModuleInstaller {
                 CrashKeyIndex.EMULATED_MODULES, encodeCrashKeyValue(emulatedModules));
     }
 
-    /**
-     * Requests the install of a module. The install will be performed asynchronously.
-     *
-     * @param moduleName Name of the module as defined in GN.
-     * @param onFinishedListener Listener to be called once installation is finished.
-     */
-    public static void install(
-            String moduleName, OnModuleInstallFinishedListener onFinishedListener) {
+    @Override
+    public void install(String moduleName, OnModuleInstallFinishedListener onFinishedListener) {
         ThreadUtils.assertOnUiThread();
 
-        if (!sModuleNameListenerMap.containsKey(moduleName)) {
-            sModuleNameListenerMap.put(moduleName, new LinkedList<>());
+        if (!mModuleNameListenerMap.containsKey(moduleName)) {
+            mModuleNameListenerMap.put(moduleName, new LinkedList<>());
         }
         List<OnModuleInstallFinishedListener> onFinishedListeners =
-                sModuleNameListenerMap.get(moduleName);
+                mModuleNameListenerMap.get(moduleName);
         onFinishedListeners.add(onFinishedListener);
         if (onFinishedListeners.size() > 1) {
             // Request is already running.
@@ -132,56 +127,50 @@ public class ModuleInstaller {
         getBackend().install(moduleName);
     }
 
-    /**
-     * Asynchronously installs module in the background when on unmetered connection and charging.
-     * Install is best effort and may fail silently. Upon success, the module will only be available
-     * after Chrome restarts.
-     *
-     * @param moduleName Name of the module.
-     */
-    public static void installDeferred(String moduleName) {
+    @Override
+    public void installDeferred(String moduleName) {
         ThreadUtils.assertOnUiThread();
         getBackend().installDeferred(moduleName);
     }
 
-    private static void onFinished(boolean success, List<String> moduleNames) {
+    private void onFinished(boolean success, List<String> moduleNames) {
         ThreadUtils.assertOnUiThread();
 
         for (String moduleName : moduleNames) {
             List<OnModuleInstallFinishedListener> onFinishedListeners =
-                    sModuleNameListenerMap.get(moduleName);
+                    mModuleNameListenerMap.get(moduleName);
             if (onFinishedListeners == null) continue;
 
             for (OnModuleInstallFinishedListener listener : onFinishedListeners) {
                 listener.onFinished(success);
             }
-            sModuleNameListenerMap.remove(moduleName);
+            mModuleNameListenerMap.remove(moduleName);
         }
 
-        if (sModuleNameListenerMap.isEmpty()) {
-            sBackend.close();
-            sBackend = null;
+        if (mModuleNameListenerMap.isEmpty()) {
+            mBackend.close();
+            mBackend = null;
         }
 
         updateCrashKeys();
     }
 
-    private static ModuleInstallerBackend getBackend() {
-        if (sBackend == null) {
-            ModuleInstallerBackend.OnFinishedListener listener = ModuleInstaller::onFinished;
-            sBackend = CommandLine.getInstance().hasSwitch(FAKE_FEATURE_MODULE_INSTALL)
+    private ModuleInstallerBackend getBackend() {
+        if (mBackend == null) {
+            ModuleInstallerBackend.OnFinishedListener listener = this::onFinished;
+            mBackend = CommandLine.getInstance().hasSwitch(FAKE_FEATURE_MODULE_INSTALL)
                     ? new FakeModuleInstallerBackend(listener)
                     : new PlayCoreModuleInstallerBackend(listener);
         }
-        return sBackend;
+        return mBackend;
     }
 
-    private static String encodeCrashKeyValue(Set<String> moduleNames) {
+    private String encodeCrashKeyValue(Set<String> moduleNames) {
         if (moduleNames.isEmpty()) return "<none>";
         // Values with dots are interpreted as URLs. Some module names have dots in them. Make sure
         // they don't get sanitized.
         return TextUtils.join(",", moduleNames).replace('.', '$');
     }
 
-    private ModuleInstaller() {}
+    private ModuleInstallerImpl() {}
 }

components/module_installer/android/java/src-impl/org/chromium/components/module_installer/PlayCoreModuleInstallerBackend.java

@@ -20,7 +20,6 @@ import org.chromium.base.ContextUtils;
 import org.chromium.base.Log;
 import org.chromium.base.metrics.CachedMetrics.EnumeratedHistogramSample;
 import org.chromium.base.metrics.RecordHistogram;
-import org.chromium.components.module_installer.ModuleInstallerBackend.OnFinishedListener;
 
 import java.util.Collections;
 import java.util.HashMap;
@@ -93,7 +92,7 @@ import java.util.Set;
     /** Records via UMA all modules that have been requested and are currently installed. */
     public static void recordModuleAvailability() {
         // MUST call init before creating a SplitInstallManager.
-        ModuleInstaller.init();
+        ModuleInstaller.getInstance().init();
         SharedPreferences prefs = ContextUtils.getAppSharedPreferences();
         Set<String> requestedModules = new HashSet<>();
         requestedModules.addAll(
@@ -128,7 +127,7 @@ import java.util.Set;
     public PlayCoreModuleInstallerBackend(OnFinishedListener listener) {
         super(listener);
         // MUST call init before creating a SplitInstallManager.
-        ModuleInstaller.init();
+        ModuleInstaller.getInstance().init();
         mManager = SplitInstallManagerFactory.create(ContextUtils.getApplicationContext());
         mManager.registerListener(this);
     }

components/module_installer/android/java/src-stub/org/chromium/components/module_installer/ModuleInstaller.java → components/module_installer/android/java/src-stub/org/chromium/components/module_installer/ModuleInstallerImpl.java

@@ -4,33 +4,29 @@
 
 package org.chromium.components.module_installer;
 
-import android.content.Context;
-
-import org.chromium.base.VisibleForTesting;
-
 /** Dummy fallback of ModuleInstaller for APK builds. */
-public class ModuleInstaller {
-    public static void init() {}
+public class ModuleInstallerImpl implements ModuleInstaller {
+    /** A valid singleton instance is necessary for tests to swap it out. */
+    private static ModuleInstaller sInstance = new ModuleInstallerImpl();
 
-    public static void initActivity(Context context) {}
-
-    public static void recordModuleAvailability() {}
+    /** Returns the singleton instance. */
+    public static ModuleInstaller getInstance() {
+        return sInstance;
+    }
 
-    public static void updateCrashKeys(){};
+    public static void setInstanceForTesting(ModuleInstaller moduleInstaller) {
+        sInstance = moduleInstaller;
+    }
 
-    public static void install(
-            String moduleName, OnModuleInstallFinishedListener onFinishedListener) {
+    @Override
+    public void install(String moduleName, OnModuleInstallFinishedListener onFinishedListener) {
         throw new UnsupportedOperationException("Cannot install module if APK");
     }
 
-    public static void installDeferred(String moduleName) {
+    @Override
+    public void installDeferred(String moduleName) {
         throw new UnsupportedOperationException("Cannot deferred install module if APK");
     }
 
-    @VisibleForTesting
-    public static boolean didRequestDeferred(String moduleName) {
-        throw new UnsupportedOperationException();
-    }
-
-    private ModuleInstaller() {}
+    private ModuleInstallerImpl() {}
 }

components/module_installer/android/java/src-test/org/chromium/components/module_installer/ModuleInstaller.java

-// Copyright 2019 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package org.chromium.components.module_installer;
-
-import android.content.Context;
-
-import org.chromium.base.VisibleForTesting;
-
-import java.util.HashSet;
-import java.util.Set;
-
-/** Mock ModuleInstaller for use in tests. */
-public class ModuleInstaller {
-    private static Set<String> sModulesRequestedDeffered = new HashSet<>();
-
-    public static void init() {}
-
-    public static void initActivity(Context context) {}
-
-    public static void recordModuleAvailability() {}
-
-    public static void updateCrashKeys(){};
-
-    public static void install(
-            String moduleName, OnModuleInstallFinishedListener onFinishedListener) {}
-
-    public static void installDeferred(String moduleName) {
-        sModulesRequestedDeffered.add(moduleName);
-    }
-
-    @VisibleForTesting
-    public static boolean didRequestDeferred(String moduleName) {
-        return sModulesRequestedDeffered.contains(moduleName);
-    }
-
-    private ModuleInstaller() {}
-}

components/module_installer/android/javatests/src/org/chromium/components/module_installer/ModuleInstallerRule.java

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.components.module_installer;
+
+import org.junit.rules.ExternalResource;
+
+/**
+ * This rule allows the caller to specify their own {@link ModuleInstaller} for the duration of the
+ * test and resets it back to what it was before.
+ *
+ * TODO(wnwen): This should eventually become ModuleConfigRule.
+ */
+public class ModuleInstallerRule extends ExternalResource {
+    private ModuleInstaller mOldModuleInstaller;
+    private final ModuleInstaller mMockModuleInstaller;
+
+    public ModuleInstallerRule(ModuleInstaller mockModuleInstaller) {
+        mMockModuleInstaller = mockModuleInstaller;
+    }
+
+    @Override
+    protected void before() {
+        mOldModuleInstaller = ModuleInstaller.getInstance();
+        ModuleInstaller.setInstanceForTesting(mMockModuleInstaller);
+    }
+
+    @Override
+    protected void after() {
+        ModuleInstaller.setInstanceForTesting(mOldModuleInstaller);
+    }
+}