diff --git a/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/JSBundleLoader.java b/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/JSBundleLoader.java
index 7b4d6e499..6615c75c8 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/JSBundleLoader.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/JSBundleLoader.java
@@ -14,6 +14,8 @@ import android.content.Context;
 import com.facebook.react.devsupport.DebugServerException;
 import com.facebook.react.devsupport.DevServerHelper;
 
+import java.io.File;
+
 /**
  * A class that stores JS bundle information and allows {@link CatalystInstance} to load a correct
  * bundle through {@link ReactBridge}.
@@ -99,6 +101,19 @@ public abstract class JSBundleLoader {
     };
   }
 
+  public static JSBundleLoader createUnpackingBundleLoader(
+      final Context context,
+      final String sourceURL,
+      final String bundleName) {
+    return UnpackingJSBundleLoader.newBuilder()
+      .setContext(context)
+      .setSourceURL(sourceURL)
+      .setDestinationPath(new File(context.getFilesDir(), "optimized-bundle"))
+      .checkAndUnpackFile(bundleName + ".meta", "bundle.meta")
+      .unpackFile(bundleName, "bundle.js")
+      .build();
+  }
+
   public abstract void loadScript(CatalystInstanceImpl instance);
   public abstract String getSourceUrl();
 }
diff --git a/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoader.java b/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoader.java
new file mode 100644
index 000000000..ed65860ff
--- /dev/null
+++ b/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoader.java
@@ -0,0 +1,342 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.cxxbridge;
+
+import android.content.Context;
+import android.content.res.AssetManager;
+
+import com.facebook.infer.annotation.Assertions;
+import com.facebook.soloader.FileLocker;
+import com.facebook.soloader.SysUtil;
+import com.facebook.systrace.Systrace;
+
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.RandomAccessFile;
+import java.util.ArrayList;
+import java.util.Arrays;
+
+import javax.annotation.Nullable;
+
+import static com.facebook.systrace.Systrace.TRACE_TAG_REACT_JAVA_BRIDGE;
+
+/**
+ * JSBundleLoader capable of unpacking specified files necessary for executing
+ * JS bundle stored in optimized format.
+ */
+public class UnpackingJSBundleLoader extends JSBundleLoader {
+
+  /**
+   * Name of the lock files. Multiple processes can be spawned off the same app
+   * and we need to guarantee that at most one unpacks files at any time. To
+   * make that work any process is required to hold file system lock on
+   * LOCK_FILE when checking whether files should be unpacked and unpacking
+   * them.
+   */
+  static final String LOCK_FILE = "unpacking-bundle-loader.lock";
+
+  /**
+   * Existence of this file indicates that the last unpacking operation finished
+   * before the app was killed or crashed. File with this name is created in the
+   * destination directory as the last one. If it is present it means that
+   * all the files that needed to be fsynced were fsynced and their content is
+   * what it should be.
+   */
+  static final String DOT_UNPACKED_FILE = ".unpacked";
+
+  private static final int IO_BUFFER_SIZE = 16 * 1024;
+
+  /**
+   * Where all the files should go to.
+   */
+  private final File mDirectoryPath;
+
+  private final String mSourceURL;
+  private final Context mContext;
+
+  /**
+   * Description of what needs to be unpacked.
+   */
+  private final Unpacker[] mUnpackers;
+
+  /* package */ UnpackingJSBundleLoader(Builder builder) {
+    mContext = Assertions.assertNotNull(builder.context);
+    mDirectoryPath = Assertions.assertNotNull(builder.destinationPath);
+    mSourceURL = Assertions.assertNotNull(builder.sourceURL);
+    mUnpackers = builder.unpackers.toArray(new Unpacker[builder.unpackers.size()]);
+  }
+
+  /**
+   * Checks if any file needs to be extracted again, and if so, clears the destination
+   * directory and unpacks everything again.
+   */
+  /* package */ void prepare() {
+    final File lockFilePath = new File(mContext.getFilesDir(), LOCK_FILE);
+    Systrace.beginSection(TRACE_TAG_REACT_JAVA_BRIDGE, "UnpackingJSBundleLoader.prepare");
+    try (FileLocker lock = FileLocker.lock(lockFilePath)) {
+      prepareLocked();
+    } catch (IOException ioe) {
+      throw new RuntimeException(ioe);
+    } finally {
+      Systrace.endSection(TRACE_TAG_REACT_JAVA_BRIDGE);
+    }
+  }
+
+  private void prepareLocked() throws IOException {
+    final File dotFinishedFilePath = new File(mDirectoryPath, DOT_UNPACKED_FILE);
+    boolean shouldReconstruct = !mDirectoryPath.exists() || !dotFinishedFilePath.exists();
+
+    byte[] buffer = new byte[IO_BUFFER_SIZE];
+    for (int i = 0; i < mUnpackers.length && !shouldReconstruct; ++i) {
+      shouldReconstruct = mUnpackers[i].shouldReconstructDir(mContext, buffer);
+    }
+
+    if (!shouldReconstruct) {
+      return;
+    }
+
+    boolean succeeded = false;
+    try {
+      SysUtil.dumbDeleteRecursive(mDirectoryPath);
+      if (!mDirectoryPath.mkdirs()) {
+        throw new IOException("Coult not create the destination directory");
+      }
+
+      for (Unpacker unpacker : mUnpackers) {
+        unpacker.unpack(mContext, buffer);
+      }
+
+      if (!dotFinishedFilePath.createNewFile()) {
+        throw new IOException("Could not create .unpacked file");
+      }
+
+      // It would be nice to fsync a few directories and files here. The thing is, if we crash and
+      // lose some data then it should be noticed on the next prepare invocation and the directory
+      // will be reconstructed. It is only crucial to fsync those files whose content is not
+      // verified on each start. Everything else is a tradeoff between perf with no crashes
+      // situation and perf when user experiences crashes. Fortunately Unpackers corresponding
+      // to files whose content is not checked handle fsyncs themselves.
+
+      succeeded = true;
+    } finally {
+      // In case of failure do yourself a favor and remove partially initialized state.
+      if (!succeeded) {
+        SysUtil.dumbDeleteRecursive(mDirectoryPath);
+      }
+    }
+  }
+
+  @Override
+  public void loadScript(CatalystInstanceImpl instance) {
+    prepare();
+    // TODO(12128379): add instance method that would take bundle directory
+    instance.loadScriptFromFile(
+      new File(mDirectoryPath, "bundle.js").getPath(),
+      mSourceURL);
+  }
+
+  @Override
+  public String getSourceUrl() {
+    return mSourceURL;
+  }
+
+  static void fsync(File path) throws IOException {
+    try (RandomAccessFile file = new RandomAccessFile(path, "r")) {
+      file.getFD().sync();
+    }
+  }
+
+  /**
+   * Reads all the bytes (but no more that maxSize) from given input stream through ioBuffer
+   * and returns byte array containing all the read bytes.
+   */
+  static byte[] readBytes(InputStream is, byte[] ioBuffer, int maxSize) throws IOException {
+    ByteArrayOutputStream baos = new ByteArrayOutputStream();
+    copyBytes(baos, is, ioBuffer, maxSize);
+    return baos.toByteArray();
+  }
+
+  /**
+   * Pumps all the bytes (but no more that maxSize) from given input stream through ioBuffer
+   * to given output stream and returns number of moved bytes.
+   */
+  static int copyBytes(
+      OutputStream os,
+      InputStream is,
+      byte[] ioBuffer,
+      int maxSize) throws IOException {
+    int totalSize = 0;
+    while (totalSize < maxSize) {
+      int rc = is.read(ioBuffer, 0, Math.min(maxSize - totalSize, ioBuffer.length));
+      if (rc == -1) {
+        break;
+      }
+      os.write(ioBuffer, 0, rc);
+      totalSize += rc;
+    }
+    return totalSize;
+  }
+
+  public static Builder newBuilder() {
+    return new Builder();
+  }
+
+  public static class Builder {
+    private @Nullable Context context;
+    private @Nullable File destinationPath;
+    private @Nullable String sourceURL;
+    private final ArrayList<Unpacker> unpackers;
+
+    public Builder() {
+      this.unpackers = new ArrayList<Unpacker>();
+      context = null;
+      destinationPath = null;
+      sourceURL = null;
+    }
+
+    public Builder setContext(Context context) {
+      this.context = context;
+      return this;
+    }
+
+    public Builder setDestinationPath(File destinationPath) {
+      this.destinationPath = destinationPath;
+      return this;
+    }
+
+    public Builder setSourceURL(String sourceURL) {
+      this.sourceURL = sourceURL;
+      return this;
+    }
+
+    /**
+     * Adds a file for unpacking. Content of extracted file is not checked on each
+     * start against content of the file bundled in apk.
+     */
+    public Builder unpackFile(String nameInApk, String destFileName) {
+      unpackers.add(new ExistenceCheckingUnpacker(nameInApk, destFileName));
+      return this;
+    }
+
+    /**
+     * Adds a file for unpacking. Content of extracted file is compared on each
+     * start with content of the same file bundled in apk. It is usefull for
+     * detecting bundle/app changes.
+     */
+    public Builder checkAndUnpackFile(String nameInApk, String destFileName) {
+      unpackers.add(new ContentCheckingUnpacker(nameInApk, destFileName));
+      return this;
+    }
+
+    /**
+     * Adds arbitrary unpacker. Usefull for injecting mocks.
+     */
+    Builder addUnpacker(Unpacker u) {
+      unpackers.add(u);
+      return this;
+    }
+
+    public UnpackingJSBundleLoader build() {
+      Assertions.assertNotNull(destinationPath);
+      for (int i = 0; i < unpackers.size(); ++i) {
+        unpackers.get(i).setDestinationDirectory(destinationPath);
+      }
+      return new UnpackingJSBundleLoader(this);
+    }
+  }
+
+  /**
+   * Abstraction for dealing with unpacking single file from apk.
+   */
+  static abstract class Unpacker {
+    protected final String mNameInApk;
+    private final String mFileName;
+    protected @Nullable File mDestinationFilePath;
+
+    public Unpacker(String nameInApk, String fileName) {
+      mNameInApk = nameInApk;
+      mFileName = fileName;
+    }
+
+    public void setDestinationDirectory(File destinationDirectoryPath) {
+      mDestinationFilePath = new File(destinationDirectoryPath, mFileName);
+    }
+
+    public abstract boolean shouldReconstructDir(Context context, byte[] ioBuffer)
+      throws IOException;
+
+    public void unpack(Context context, byte[] ioBuffer) throws IOException {
+      AssetManager am = context.getAssets();
+      try (InputStream is = am.open(mNameInApk, AssetManager.ACCESS_STREAMING)) {
+        try (FileOutputStream fileOutputStream = new FileOutputStream(
+               Assertions.assertNotNull(mDestinationFilePath))) {
+          copyBytes(fileOutputStream, is, ioBuffer, Integer.MAX_VALUE);
+        }
+      }
+    }
+  }
+
+  /**
+   * Deals with unpacking files whose content is not checked on each start and
+   * need to be fsynced after unpacking.
+   */
+  static class ExistenceCheckingUnpacker extends Unpacker {
+    public ExistenceCheckingUnpacker(String nameInApk, String fileName) {
+      super(nameInApk, fileName);
+    }
+
+    @Override
+    public boolean shouldReconstructDir(Context context, byte[] ioBuffer) {
+      return !Assertions.assertNotNull(mDestinationFilePath).exists();
+    }
+
+    @Override
+    public void unpack(Context context, byte[] ioBuffer) throws IOException {
+      super.unpack(context, ioBuffer);
+      fsync(Assertions.assertNotNull(mDestinationFilePath));
+    }
+  }
+
+  /**
+   * Deals with unpacking files whose content is checked on each start and thus
+   * do not require fsync.
+   */
+  static class ContentCheckingUnpacker extends Unpacker {
+    public ContentCheckingUnpacker(String nameInApk, String fileName) {
+      super(nameInApk, fileName);
+    }
+
+    @Override
+    public boolean shouldReconstructDir(Context context, byte[] ioBuffer) throws IOException {
+      if (!Assertions.assertNotNull(mDestinationFilePath).exists()) {
+        return true;
+      }
+
+      AssetManager am = context.getAssets();
+      final byte[] assetContent;
+      try (InputStream assetStream = am.open(mNameInApk, AssetManager.ACCESS_STREAMING)) {
+        assetContent = readBytes(assetStream, ioBuffer, Integer.MAX_VALUE);
+      }
+
+      final byte[] fileContent;
+      try (InputStream fileStream = new FileInputStream(
+             Assertions.assertNotNull(mDestinationFilePath))) {
+        fileContent = readBytes(fileStream, ioBuffer, assetContent.length + 1);
+      }
+
+      return !Arrays.equals(assetContent, fileContent);
+    }
+  }
+}
diff --git a/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/BUCK b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/BUCK
new file mode 100644
index 000000000..22c014b06
--- /dev/null
+++ b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/BUCK
@@ -0,0 +1,40 @@
+include_defs('//ReactAndroid/DEFS')
+
+STANDARD_TEST_SRCS = [
+  '*Test.java',
+]
+
+android_library(
+  name = 'testhelpers',
+  srcs = glob(['*.java'], excludes = STANDARD_TEST_SRCS),
+  deps = [
+    react_native_dep('third-party/java/junit:junit'),
+    react_native_dep('third-party/java/mockito:mockito'),
+  ],
+  visibility = [
+    'PUBLIC'
+  ],
+)
+
+robolectric3_test(
+  name = 'bridge',
+  # Please change the contact to the oncall of your team
+  contacts = ['oncall+fbandroid_sheriff@xmail.facebook.com'],
+  srcs = glob(STANDARD_TEST_SRCS),
+  deps = [
+    ':testhelpers',
+    react_native_dep('libraries/fbcore/src/test/java/com/facebook/powermock:powermock'),
+    react_native_dep('libraries/soloader/java/com/facebook/soloader:soloader'),
+    react_native_dep('third-party/java/junit:junit'),
+    react_native_dep('third-party/java/mockito:mockito'),
+    react_native_dep('third-party/java/robolectric3/robolectric:robolectric'),
+    react_native_target('java/com/facebook/react/cxxbridge:bridge'),
+  ],
+  visibility = [
+    'PUBLIC'
+  ],
+)
+
+project_config(
+  test_target = ':bridge',
+)
diff --git a/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/ContentCheckingUnpackerTest.java b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/ContentCheckingUnpackerTest.java
new file mode 100644
index 000000000..23ba3ca67
--- /dev/null
+++ b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/ContentCheckingUnpackerTest.java
@@ -0,0 +1,85 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.cxxbridge;
+
+import java.io.FileDescriptor;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.InputStream;
+import java.io.IOException;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.runner.RunWith;
+import org.junit.Test;
+import org.powermock.core.classloader.annotations.PowerMockIgnore;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.rule.PowerMockRule;
+import org.robolectric.RobolectricTestRunner;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.times;
+import static org.powermock.api.mockito.PowerMockito.mockStatic;
+import static org.powermock.api.mockito.PowerMockito.verifyStatic;
+
+@PrepareForTest({UnpackingJSBundleLoader.class})
+@PowerMockIgnore({ "org.mockito.*", "org.robolectric.*", "android.*" })
+@RunWith(RobolectricTestRunner.class)
+public class ContentCheckingUnpackerTest extends UnpackerTestBase {
+  @Rule
+  public PowerMockRule rule = new PowerMockRule();
+
+  private UnpackingJSBundleLoader.ContentCheckingUnpacker mUnpacker;
+
+  @Before
+  public void setUp() throws IOException {
+    super.setUp();
+    mUnpacker = new UnpackingJSBundleLoader.ContentCheckingUnpacker(
+      NAME_IN_APK,
+      DESTINATION_NAME);
+    mUnpacker.setDestinationDirectory(folder.getRoot());
+  }
+
+  @Test
+  public void testReconstructsIfFileDoesNotExist() throws IOException {
+    assertTrue(mUnpacker.shouldReconstructDir(mContext, mIOBuffer));
+  }
+
+  @Test
+  public void testReconstructsIfContentDoesNotMatch() throws IOException {
+    try (FileOutputStream fos = new FileOutputStream(mDestinationPath)) {
+      fos.write(ASSET_DATA, 0, ASSET_DATA.length - 1);
+      fos.write((byte) (ASSET_DATA[ASSET_DATA.length - 1] + 1));
+    }
+    assertTrue(mUnpacker.shouldReconstructDir(mContext, mIOBuffer));
+  }
+
+  @Test
+  public void testDoesNotReconstructIfContentMatches() throws IOException {
+    try (FileOutputStream fos = new FileOutputStream(mDestinationPath)) {
+      fos.write(ASSET_DATA);
+    }
+    assertFalse(mUnpacker.shouldReconstructDir(mContext, mIOBuffer));
+  }
+
+  @Test
+  public void testUnpacksFile() throws IOException {
+    mUnpacker.unpack(mContext, mIOBuffer);
+    assertTrue(mDestinationPath.exists());
+    try (InputStream is = new FileInputStream(mDestinationPath)) {
+      byte[] storedData = UnpackingJSBundleLoader.readBytes(is, mIOBuffer, Integer.MAX_VALUE);
+      assertArrayEquals(ASSET_DATA, storedData);
+    }
+  }
+}
diff --git a/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/ExistenceCheckingUnpackerTest.java b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/ExistenceCheckingUnpackerTest.java
new file mode 100644
index 000000000..2608bcab3
--- /dev/null
+++ b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/ExistenceCheckingUnpackerTest.java
@@ -0,0 +1,78 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.cxxbridge;
+
+import java.io.FileInputStream;
+import java.io.InputStream;
+import java.io.IOException;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.runner.RunWith;
+import org.junit.Test;
+import org.powermock.core.classloader.annotations.PowerMockIgnore;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.rule.PowerMockRule;
+import org.robolectric.RobolectricTestRunner;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.times;
+import static org.powermock.api.mockito.PowerMockito.mockStatic;
+import static org.powermock.api.mockito.PowerMockito.verifyStatic;
+
+@PrepareForTest({UnpackingJSBundleLoader.class})
+@PowerMockIgnore({ "org.mockito.*", "org.robolectric.*", "android.*" })
+@RunWith(RobolectricTestRunner.class)
+public class ExistenceCheckingUnpackerTest extends UnpackerTestBase {
+  @Rule
+  public PowerMockRule rule = new PowerMockRule();
+
+  private UnpackingJSBundleLoader.ExistenceCheckingUnpacker mUnpacker;
+
+  @Before
+  public void setUp() throws IOException {
+    super.setUp();
+    mUnpacker = new UnpackingJSBundleLoader.ExistenceCheckingUnpacker(
+      NAME_IN_APK,
+      DESTINATION_NAME);
+    mUnpacker.setDestinationDirectory(folder.getRoot());
+  }
+
+  @Test
+  public void testReconstructsIfFileDoesNotExist() {
+    assertTrue(mUnpacker.shouldReconstructDir(mContext, mIOBuffer));
+  }
+
+  @Test
+  public void testDoesNotReconstructIfFileExists() throws IOException {
+    mDestinationPath.createNewFile();
+    assertFalse(mUnpacker.shouldReconstructDir(mContext, mIOBuffer));
+  }
+
+  @Test
+  public void testUnpacksFile() throws IOException {
+    mUnpacker.unpack(mContext, mIOBuffer);
+    assertTrue(mDestinationPath.exists());
+    try (InputStream is = new FileInputStream(mDestinationPath)) {
+      byte[] storedData = UnpackingJSBundleLoader.readBytes(is, mIOBuffer, Integer.MAX_VALUE);
+      assertArrayEquals(ASSET_DATA, storedData);
+    }
+  }
+
+  @Test
+  public void testFsyncsAfterUnpacking() throws IOException {
+    mockStatic(UnpackingJSBundleLoader.class);
+    mUnpacker.unpack(mContext, mIOBuffer);
+    verifyStatic(times(1));
+    UnpackingJSBundleLoader.fsync(mDestinationPath);
+  }
+}
diff --git a/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/UnpackerTestBase.java b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/UnpackerTestBase.java
new file mode 100644
index 000000000..a2865a612
--- /dev/null
+++ b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/UnpackerTestBase.java
@@ -0,0 +1,95 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.cxxbridge;
+
+import android.content.Context;
+import android.content.res.AssetManager;
+
+import java.io.ByteArrayInputStream;
+import java.io.File;
+import java.io.FileDescriptor;
+import java.io.FileInputStream;
+import java.io.InputStream;
+import java.io.IOException;
+
+import org.junit.Rule;
+import org.junit.rules.TemporaryFolder;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.anyInt;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class UnpackerTestBase {
+  static final String NAME_IN_APK = "nameInApk";
+  static final String DESTINATION_NAME = "destination";
+  static final byte[] ASSET_DATA = new byte[]{(byte) 1, (byte) 101, (byte) 50};
+
+  @Rule
+  public TemporaryFolder folder = new TemporaryFolder();
+
+  File mDestinationPath;
+  byte[] mIOBuffer;
+
+  Context mContext;
+  AssetManager mAssetManager;
+
+  public void setUp() throws IOException {
+    mDestinationPath = new File(folder.getRoot(), DESTINATION_NAME);
+    mIOBuffer = new byte[16 * 1024];
+
+    mContext = mock(Context.class);
+    mAssetManager = mock(AssetManager.class);
+
+    when(mContext.getAssets()).thenReturn(mAssetManager);
+    when(mAssetManager.open(eq(NAME_IN_APK), anyInt()))
+      .then(new Answer<FileInputStream>() {
+          @Override
+          public FileInputStream answer(InvocationOnMock invocation) throws Throwable {
+            final ByteArrayInputStream bais = new ByteArrayInputStream(ASSET_DATA);
+            final FileInputStream fis = mock(FileInputStream.class);
+            when(fis.read())
+              .then(new Answer<Integer>() {
+                  @Override
+                  public Integer answer(InvocationOnMock invocation) throws Throwable {
+                    return bais.read();
+                  }
+                });
+            when(fis.read(any(byte[].class)))
+              .then(new Answer<Integer>() {
+                  @Override
+                    public Integer answer(InvocationOnMock invocation) throws Throwable {
+                    return bais.read((byte[]) invocation.getArguments()[0]);
+                  }
+                });
+            when(fis.read(any(byte[].class), any(int.class), any(int.class)))
+              .then(new Answer<Integer>() {
+                  @Override
+                    public Integer answer(InvocationOnMock invocation) throws Throwable {
+                    return bais.read(
+                      (byte[]) invocation.getArguments()[0],
+                      (int) invocation.getArguments()[1],
+                      (int) invocation.getArguments()[2]);
+                  }
+                });
+            when(fis.available()).then(new Answer<Integer>() {
+                @Override
+                public Integer answer(InvocationOnMock invocation) throws Throwable {
+                  return bais.available();
+                }
+              });
+            return fis;
+          }
+        });
+  }
+}
diff --git a/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoaderTest.java b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoaderTest.java
new file mode 100644
index 000000000..d6a2b9c66
--- /dev/null
+++ b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoaderTest.java
@@ -0,0 +1,183 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.cxxbridge;
+
+import android.content.Context;
+
+import com.facebook.soloader.SoLoader;
+
+import java.io.File;
+import java.io.IOException;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.rules.TemporaryFolder;
+import org.junit.runner.RunWith;
+import org.junit.Test;
+import org.robolectric.RobolectricTestRunner;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Matchers.same;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+
+@RunWith(RobolectricTestRunner.class)
+public class UnpackingJSBundleLoaderTest {
+  static {
+    SoLoader.setInTestMode();
+  }
+
+  private static final String URL = "http://this.is.an.url";
+  private static final int MOCK_UNPACKERS_NUM = 2;
+
+  @Rule
+  public TemporaryFolder folder = new TemporaryFolder();
+
+  private File mDestinationPath;
+  private File mFilesPath;
+
+  private UnpackingJSBundleLoader.Builder mBuilder;
+  private Context mContext;
+  private CatalystInstanceImpl mCatalystInstanceImpl;
+  private UnpackingJSBundleLoader.Unpacker[] mMockUnpackers;
+
+  @Before
+  public void setUp() throws IOException {
+    mDestinationPath = folder.newFolder("destination");
+    mFilesPath = folder.newFolder("files");
+
+    mContext = mock(Context.class);
+    when(mContext.getFilesDir()).thenReturn(mFilesPath);
+
+    mCatalystInstanceImpl = mock(CatalystInstanceImpl.class);
+
+    mBuilder = UnpackingJSBundleLoader.newBuilder()
+      .setDestinationPath(mDestinationPath)
+      .setSourceURL(URL)
+      .setContext(mContext);
+
+    mMockUnpackers = new UnpackingJSBundleLoader.Unpacker[MOCK_UNPACKERS_NUM];
+    for (int i = 0; i < mMockUnpackers.length; ++i) {
+      mMockUnpackers[i] = mock(UnpackingJSBundleLoader.Unpacker.class);
+    }
+  }
+
+  private void addUnpackers() {
+    for (UnpackingJSBundleLoader.Unpacker unpacker : mMockUnpackers) {
+      mBuilder.addUnpacker(unpacker);
+    }
+  }
+
+  @Test
+  public void testGetSourceUrl() {
+    assertEquals(URL, mBuilder.build().getSourceUrl());
+  }
+
+  @Test
+  public void testCreatesDotUnpackedFile() throws IOException {
+    mBuilder.build().prepare();
+    assertTrue(new File(mDestinationPath, UnpackingJSBundleLoader.DOT_UNPACKED_FILE).exists());
+  }
+
+  @Test
+  public void testCreatesLockFile() throws IOException {
+    mBuilder.build().prepare();
+    assertTrue(new File(mFilesPath, UnpackingJSBundleLoader.LOCK_FILE).exists());
+  }
+
+  @Test
+  public void testCallsAppropriateInstanceMethod() throws IOException {
+    mBuilder.build().loadScript(mCatalystInstanceImpl);
+    verify(mCatalystInstanceImpl).loadScriptFromFile(
+      eq(new File(mDestinationPath, "bundle.js").getPath()),
+      eq(URL));
+    verifyNoMoreInteractions(mCatalystInstanceImpl);
+  }
+
+  @Test
+  public void testLoadScriptUnpacks() {
+    mBuilder.build().loadScript(mCatalystInstanceImpl);
+    assertTrue(new File(mDestinationPath, UnpackingJSBundleLoader.DOT_UNPACKED_FILE).exists());
+  }
+
+  @Test
+  public void testPrepareCallDoesNotRecreateDirIfNotNecessary() throws IOException {
+    mBuilder.build().prepare();
+
+    addUnpackers();
+    mBuilder.build().prepare();
+    for (UnpackingJSBundleLoader.Unpacker unpacker : mMockUnpackers) {
+      verify(unpacker).setDestinationDirectory(mDestinationPath);
+      verify(unpacker).shouldReconstructDir(
+        same(mContext),
+        any(byte[].class));
+      verifyNoMoreInteractions(unpacker);
+    }
+  }
+
+  @Test
+  public void testShouldReconstructDirForcesRecreation() throws IOException {
+    mBuilder.build().prepare();
+
+    addUnpackers();
+    when(mMockUnpackers[0].shouldReconstructDir(
+           same(mContext),
+           any(byte[].class)))
+      .thenReturn(true);
+    mBuilder.build().prepare();
+
+    verify(mMockUnpackers[0]).shouldReconstructDir(
+      same(mContext),
+      any(byte[].class));
+    for (UnpackingJSBundleLoader.Unpacker unpacker : mMockUnpackers) {
+      verify(unpacker).setDestinationDirectory(mDestinationPath);
+      verify(unpacker).unpack(
+        same(mContext),
+        any(byte[].class));
+      verifyNoMoreInteractions(unpacker);
+    }
+  }
+
+  @Test
+  public void testDirectoryReconstructionRemovesDir() throws IOException {
+    mBuilder.build().prepare();
+    final File aFile = new File(mDestinationPath, "a_file");
+    aFile.createNewFile();
+
+    when(mMockUnpackers[0].shouldReconstructDir(
+           same(mContext),
+           any(byte[].class)))
+      .thenReturn(true);
+    addUnpackers();
+    mBuilder.build().prepare();
+
+    assertFalse(aFile.exists());
+  }
+
+  @Test(expected = RuntimeException.class)
+  public void testDropsDirectoryOnException() throws IOException {
+    doThrow(new IOException("An expected IOException"))
+      .when(mMockUnpackers[0]).unpack(
+        same(mContext),
+        any(byte[].class));
+    try {
+      mBuilder.addUnpacker(mMockUnpackers[0]).build().prepare();
+    } finally {
+      assertFalse(mDestinationPath.exists());
+    }
+  }
+}