diff --git a/.classpath b/.classpath
index 890e9d5..fe8a63d 100644
--- a/.classpath
+++ b/.classpath
@@ -25,7 +25,7 @@
 	<classpathentry kind="var" path="TRADEFED_ROOT/out/soong/.intermediates/external/perfetto/perfetto_config-full/linux_glibc_common/combined/perfetto_config-full.jar"/>
 	<classpathentry kind="var" path="TRADEFED_ROOT/out/soong/.intermediates/tools/tradefederation/core/tradefed-grpc-lib-1.0.1/linux_glibc_common/combined/tradefed-grpc-lib-1.0.1.jar"/>
 	<classpathentry kind="var" path="TRADEFED_ROOT/out/soong/.intermediates/platform_testing/libraries/aoa-helper/aoa-helper/linux_glibc_common/combined/aoa-helper.jar"/>
-	<classpathentry kind="var" path="TRADEFED_ROOT/prebuilts/tools/common/google-api-java-client/1.23.0/google-api-java-client-min-repackaged-1.23.0.jar"/>
+	<classpathentry exported="true" kind="var" path="TRADEFED_ROOT/prebuilts/tools/common/google-api-java-client/1.23.0/google-api-java-client-min-repackaged-1.23.0.jar"/>
 	<classpathentry kind="var" path="TRADEFED_ROOT/out/soong/.intermediates/prebuilts/tools/common/google-api-services-compute/google-api-services-compute/linux_glibc_common/combined/google-api-services-compute.jar"/>
 	<classpathentry kind="var" path="TRADEFED_ROOT/prebuilts/misc/common/frameworks/platformprotos-prebuilt.jar"/>
 	<classpathentry kind="output" path="bin"/>
diff --git a/src/com/android/tradefed/util/FileUtil.java b/src/com/android/tradefed/util/FileUtil.java
index 607c4fe..2ba2ba8 100644
--- a/src/com/android/tradefed/util/FileUtil.java
+++ b/src/com/android/tradefed/util/FileUtil.java
@@ -1036,6 +1036,18 @@
     }
 
     /**
+     * Helper method to calculate base64 md5 for a file.
+     *
+     * @param file
+     * @return md5 of the file
+     * @throws IOException
+     */
+    public static String calculateBase64Md5(File file) throws IOException {
+        FileInputStream inputSource = new FileInputStream(file);
+        return StreamUtil.calculateBase64Md5(inputSource);
+    }
+
+    /**
      * Converts an integer representing unix mode to a set of {@link PosixFilePermission}s
      */
     public static Set<PosixFilePermission> unixModeToPosix(int mode) {
diff --git a/src/com/android/tradefed/util/GCSBucketUtil.java b/src/com/android/tradefed/util/GCSBucketUtil.java
index 614bcf2..0854274 100644
--- a/src/com/android/tradefed/util/GCSBucketUtil.java
+++ b/src/com/android/tradefed/util/GCSBucketUtil.java
@@ -32,8 +32,9 @@
 /**
  * File manager to download and upload files from Google Cloud Storage (GCS).
  *
- * This class should NOT be used from the scope of a test (i.e., IRemoteTest).
+ * <p>This class should NOT be used from the scope of a test (i.e., IRemoteTest).
  */
+@Deprecated
 public class GCSBucketUtil {
 
     // https://cloud.google.com/storage/docs/gsutil
diff --git a/src/com/android/tradefed/util/GCSFileDownloader.java b/src/com/android/tradefed/util/GCSFileDownloader.java
index 8a54add..5fbb98b 100644
--- a/src/com/android/tradefed/util/GCSFileDownloader.java
+++ b/src/com/android/tradefed/util/GCSFileDownloader.java
@@ -19,16 +19,25 @@
 import com.android.tradefed.build.BuildRetrievalError;
 import com.android.tradefed.build.IFileDownloader;
 import com.android.tradefed.log.LogUtil.CLog;
-import com.android.tradefed.util.GCSBucketUtil.GCSFileMetadata;
 
+import com.google.auth.Credentials;
+import com.google.auth.oauth2.ServiceAccountCredentials;
+import com.google.auth.oauth2.UserCredentials;
+import com.google.cloud.storage.Blob;
+import com.google.cloud.storage.Bucket;
+import com.google.cloud.storage.Storage;
+import com.google.cloud.storage.Storage.BlobListOption;
+import com.google.cloud.storage.StorageException;
+import com.google.cloud.storage.StorageOptions;
 import com.google.common.annotations.VisibleForTesting;
 
-import java.io.ByteArrayInputStream;
 import java.io.File;
+import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.nio.file.Path;
+import java.nio.channels.Channels;
 import java.nio.file.Paths;
+import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.regex.Matcher;
@@ -39,12 +48,18 @@
     public static final String GCS_PREFIX = "gs://";
     public static final String GCS_APPROX_PREFIX = "gs:/";
 
-    private static final long TIMEOUT = 10 * 60 * 1000; // 10minutes
-    private static final long RETRY_INTERVAL = 1000; // 1s
-    private static final int ATTETMPTS = 3;
-    private static final Pattern GCS_PATH_PATTERN = Pattern.compile("gs://([^/]*)(/.*)");
+    private static final Pattern GCS_PATH_PATTERN = Pattern.compile("gs://([^/]*)/(.*)");
     private static final String PATH_SEP = "/";
 
+    private File mJsonKeyFile = null;
+    private Storage mStorage;
+
+    public GCSFileDownloader(File jsonKeyFile) {
+        mJsonKeyFile = jsonKeyFile;
+    }
+
+    public GCSFileDownloader() {}
+
     /**
      * Download a file from a GCS bucket file.
      *
@@ -53,10 +68,46 @@
      * @return {@link InputStream} with the file content.
      */
     public InputStream downloadFile(String bucketName, String filename) throws IOException {
-        GCSBucketUtil bucket = getGCSBucketUtil(bucketName);
-        Path path = Paths.get(filename);
-        String contents = bucket.pullContents(path);
-        return new ByteArrayInputStream(contents.getBytes());
+        try {
+            Blob blob = getBucket(bucketName).get(filename);
+            if (blob == null) {
+                throw new IOException(
+                        String.format("gs://%s/%s doesn't exist.", bucketName, filename));
+            }
+            return Channels.newInputStream(blob.reader());
+        } catch (StorageException e) {
+            throw new IOException(e);
+        }
+    }
+
+    Storage getStorage() throws IOException {
+        if (mStorage == null) {
+            Credentials credential = null;
+            if (mJsonKeyFile != null && mJsonKeyFile.exists()) {
+                CLog.d("Using json key file %s.", mJsonKeyFile);
+                credential =
+                        ServiceAccountCredentials.fromStream(new FileInputStream(mJsonKeyFile));
+            } else {
+                CLog.d("Using local authentication.");
+                try {
+                    credential = UserCredentials.getApplicationDefault();
+                } catch (IOException e) {
+                    CLog.e(e.getMessage());
+                    CLog.e("Try 'gcloud auth application-default login' to login.");
+                    throw e;
+                }
+            }
+            mStorage = StorageOptions.newBuilder().setCredentials(credential).build().getService();
+        }
+        return mStorage;
+    }
+
+    Bucket getBucket(String bucketName) throws IOException, StorageException {
+        Bucket bucket = getStorage().get(bucketName);
+        if (bucket == null) {
+            throw new IOException(String.format("Bucket %s doesn't exist.", bucketName));
+        }
+        return bucket;
     }
 
     /**
@@ -86,16 +137,74 @@
         downloadFile(pathParts[0], pathParts[1], destFile);
     }
 
+
+    private boolean isFileFresh(File localFile, Blob remoteFile) throws IOException {
+        if (localFile == null && remoteFile == null) {
+            return true;
+        }
+        if (localFile == null || remoteFile == null) {
+            return false;
+        }
+        return remoteFile.getMd5().equals(FileUtil.calculateBase64Md5(localFile));
+    }
+
     @Override
     public boolean isFresh(File localFile, String remotePath) throws BuildRetrievalError {
         String[] pathParts = parseGcsPath(remotePath);
         try {
-            return recursiveCheckFreshness(localFile, pathParts[0], Paths.get(pathParts[1]));
-        } catch (IOException e) {
+            return recursiveCheckFolderFreshness(getBucket(pathParts[0]), pathParts[1], localFile);
+        } catch (IOException | StorageException e) {
             throw new BuildRetrievalError(e.getMessage(), e);
         }
     }
 
+    /**
+     * For GCS, if it's a file, we use file content's md5 hash to check if the local file is the
+     * same as the remote file. If it's a folder, we will check all the files in the folder are the
+     * same and all the sub-folders also have the same files.
+     *
+     * @param bucket is the gcs bucket.
+     * @param remoteFilename is the relative path to the bucket.
+     * @param localFile is the local file
+     * @return true if local file is the same as remote file, otherwise false.
+     * @throws IOException
+     * @throws StorageException
+     */
+    private boolean recursiveCheckFolderFreshness(
+            Bucket bucket, String remoteFilename, File localFile)
+            throws IOException, StorageException {
+        if (!localFile.exists()) {
+            return false;
+        }
+        if (localFile.isFile()) {
+            return isFileFresh(localFile, bucket.get(remoteFilename));
+        }
+        // localFile is a folder.
+        Set<String> subFilenames = new HashSet<>(Arrays.asList(localFile.list()));
+        remoteFilename = sanitizeDirectoryName(remoteFilename);
+
+        for (Blob subRemoteFile : listRemoteFilesUnderFolder(bucket, remoteFilename)) {
+            if (subRemoteFile.getName().equals(remoteFilename)) {
+                // Skip the current folder.
+                continue;
+            }
+            String subFilename = Paths.get(subRemoteFile.getName()).getFileName().toString();
+            if (!recursiveCheckFolderFreshness(
+                    bucket, subRemoteFile.getName(), new File(localFile, subFilename))) {
+                return false;
+            }
+            subFilenames.remove(subFilename);
+        }
+        return subFilenames.isEmpty();
+    }
+
+    Iterable<Blob> listRemoteFilesUnderFolder(Bucket bucket, String folder) {
+        return bucket.list(
+                        BlobListOption.prefix(sanitizeDirectoryName(folder)),
+                        BlobListOption.currentDirectory())
+                .iterateAll();
+    }
+
     String[] parseGcsPath(String remotePath) throws BuildRetrievalError {
         if (remotePath.startsWith(GCS_APPROX_PREFIX) && !remotePath.startsWith(GCS_PREFIX)) {
             // File object remove double // so we have to rebuild it in some cases
@@ -109,98 +218,66 @@
         return new String[] {m.group(1), m.group(2)};
     }
 
-    /**
-     * For GCS, if it's a file, we use file content's md5 hash to check if the local file is the
-     * same as the remote file. If it's a folder, we will check all the files in the folder are the
-     * same and all the sub-folders also have the same files.
-     *
-     * @param localFile is the local file
-     * @param bucketName is the remote file's GCS bucket name
-     * @param remotePath is the relative path to the bucket.
-     * @return true if local file is the same as remote file, otherwise false.
-     * @throws IOException
-     */
-    private boolean recursiveCheckFreshness(File localFile, String bucketName, Path remotePath)
-            throws IOException {
-        GCSBucketUtil bucketUtil = getGCSBucketUtil(bucketName);
-        if (localFile.isFile()) {
-            GCSFileMetadata fileInfo = bucketUtil.stat(remotePath);
-            boolean isFileFresh = fileInfo.mMd5Hash.equals(bucketUtil.md5Hash(localFile));
-            if (!isFileFresh) {
-                CLog.d("Local file for %s is not fresh.", remotePath);
-            }
-            return isFileFresh;
-        } else if (localFile.isDirectory()) {
-            Set<String> remoteUriSets = new HashSet<String>(bucketUtil.ls(remotePath));
-            String remoteUri = sanitizeDirectoryName(bucketUtil.getUriForGcsPath(remotePath));
-            // If the folder has files inside it, "ls" will include the folder itself.
-            // If the folder only has folders or has nothing inside it, "ls" will not include the
-            // folder itself. That said depends on folder's content, "ls" may or may not list the
-            // current folder. Since the current folder should always exists (otherwise the "ls"
-            // already throws exception), we don't bother to check it is in the "ls" result or not.
-            remoteUriSets.remove(remoteUri);
-
-            for (File subFile : localFile.listFiles()) {
-                Path remoteSubPath = remotePath.resolve(subFile.getName());
-                String remoteSubUri = bucketUtil.getUriForGcsPath(remoteSubPath);
-                if (subFile.isDirectory()) {
-                    remoteSubUri = sanitizeDirectoryName(remoteSubUri);
-                }
-                if (!remoteUriSets.contains(remoteSubUri)) {
-                    CLog.d("GCS doesn't have %s.", remoteSubUri);
-                    return false;
-                }
-                remoteUriSets.remove(remoteSubUri);
-            }
-            if (!remoteUriSets.isEmpty()) {
-                CLog.d("GCS has these files but local doesn't: %s", remoteUriSets);
-                return false;
-            }
-            for (File subFile : localFile.listFiles()) {
-                if (!recursiveCheckFreshness(
-                        subFile, bucketName, remotePath.resolve(subFile.getName()))) {
-                    return false;
-                }
-            }
-            return true;
-        }
-        return false;
-    }
-
-    /** Folder name should end with "/" */
     String sanitizeDirectoryName(String name) {
+        /** Folder name should end with "/" */
         if (!name.endsWith(PATH_SEP)) {
             name += PATH_SEP;
         }
         return name;
     }
 
+    /** check given filename is a folder or not. */
+    private boolean isFolder(Bucket bucket, String filename) throws StorageException {
+        filename = sanitizeDirectoryName(filename);
+        return bucket.list(BlobListOption.prefix(filename), BlobListOption.currentDirectory())
+                .iterateAll()
+                .iterator()
+                .hasNext();
+    }
+
     @VisibleForTesting
     void downloadFile(String bucketName, String filename, File localFile)
             throws BuildRetrievalError {
-        CLog.i("Downloading %s %s to %s", bucketName, filename, localFile.getAbsolutePath());
-
-        GCSBucketUtil bucketUtil = getGCSBucketUtil(bucketName);
         try {
-            if (!bucketUtil.isFile(filename)) {
-                filename = sanitizeDirectoryName(filename);
-                filename += "*";
-                localFile.mkdirs();
-                bucketUtil.setRecursive(true);
-            }
-            bucketUtil.pull(Paths.get(filename), localFile);
-        } catch (IOException e) {
-            CLog.e("Failed to download %s, clean up.", localFile.getAbsoluteFile());
+            recursiveDownload(getStorage().get(bucketName), filename, localFile);
+        } catch (IOException | StorageException e) {
+            CLog.e("Failed to download gs://%s/%s, clean up.", bucketName, filename);
             throw new BuildRetrievalError(e.getMessage(), e);
         }
     }
 
-    private GCSBucketUtil getGCSBucketUtil(String bucketName) {
-        GCSBucketUtil bucketUtil = new GCSBucketUtil(bucketName);
-        bucketUtil.setTimeoutMs(TIMEOUT);
-        bucketUtil.setRetryInterval(RETRY_INTERVAL);
-        bucketUtil.setAttempts(ATTETMPTS);
-        return bucketUtil;
+    private void recursiveDownload(Bucket bucket, String filepath, File localFile)
+            throws StorageException, IOException {
+        CLog.d(
+                "Downloading gs://%s/%s to %s",
+                bucket.getName(), filepath, localFile.getAbsolutePath());
+        if (!isFolder(bucket, filepath)) {
+            Blob blob = bucket.get(filepath);
+            if (blob == null) {
+                throw new IOException(
+                        String.format("gs://%s/%s doesn't exist.", bucket.getName(), filepath));
+            }
+            blob.downloadTo(localFile.toPath());
+            return;
+        }
+        // Remote file is a folder.
+        filepath = sanitizeDirectoryName(filepath);
+        if (!localFile.exists()) {
+            FileUtil.mkdirsRWX(localFile);
+        }
+        Set<String> subFilenames = new HashSet<>(Arrays.asList(localFile.list()));
+        for (Blob subRemoteFile : listRemoteFilesUnderFolder(bucket, filepath)) {
+            if (subRemoteFile.getName().equals(filepath)) {
+                // Skip the current folder.
+                continue;
+            }
+            String subFilename = Paths.get(subRemoteFile.getName()).getFileName().toString();
+            recursiveDownload(bucket, subRemoteFile.getName(), new File(localFile, subFilename));
+            subFilenames.remove(subFilename);
+        }
+        for (String subFilename : subFilenames) {
+            FileUtil.recursiveDelete(new File(localFile, subFilename));
+        }
     }
 
     /**
diff --git a/src/com/android/tradefed/util/StreamUtil.java b/src/com/android/tradefed/util/StreamUtil.java
index 6520aac..a853c15 100644
--- a/src/com/android/tradefed/util/StreamUtil.java
+++ b/src/com/android/tradefed/util/StreamUtil.java
@@ -33,6 +33,7 @@
 import java.security.DigestInputStream;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
+import java.util.Base64;
 import java.util.Objects;
 import java.util.zip.GZIPOutputStream;
 import java.util.zip.ZipOutputStream;
@@ -305,6 +306,22 @@
      * @throws IOException
      */
     public static String calculateMd5(InputStream inputSource) throws IOException {
+        return bytesToHexString(calculateMd5Digest(inputSource));
+    }
+
+    /**
+     * Helper method to calculate base64 md5 for a inputStream. The inputStream will be consumed and
+     * closed.
+     *
+     * @param inputSource used to create inputStream
+     * @return base64 md5 of the stream
+     * @throws IOException
+     */
+    public static String calculateBase64Md5(InputStream inputSource) throws IOException {
+        return Base64.getEncoder().encodeToString(calculateMd5Digest(inputSource));
+    }
+
+    private static byte[] calculateMd5Digest(InputStream inputSource) throws IOException {
         MessageDigest md = null;
         try {
             md = MessageDigest.getInstance("md5");
@@ -318,8 +335,7 @@
             // Read through the stream to update digest.
         }
         input.close();
-        String md5 = bytesToHexString(md.digest());
-        return md5;
+        return md.digest();
     }
 
     private static final char[] HEX_CHARS = {
diff --git a/tests/src/com/android/tradefed/util/FileUtilFuncTest.java b/tests/src/com/android/tradefed/util/FileUtilFuncTest.java
index 9f6aa06..a08d320 100644
--- a/tests/src/com/android/tradefed/util/FileUtilFuncTest.java
+++ b/tests/src/com/android/tradefed/util/FileUtilFuncTest.java
@@ -342,6 +342,24 @@
         }
     }
 
+    /**
+     * Verify {@link FileUtil#calculateBase64Md5(File)} works.
+     *
+     * @throws IOException
+     */
+    public void testCalculateBase64Md5() throws IOException {
+        final String source = "testtesttesttesttest";
+        final String base64Md5 = "8xf2gvr+AwnGpCOvC076WQ==";
+        File tmpFile = FileUtil.createTempFile("testCalculateMd5", ".txt");
+        try {
+            FileUtil.writeToFile(source, tmpFile);
+            String actualBase64Md5 = FileUtil.calculateBase64Md5(tmpFile);
+            assertEquals(base64Md5, actualBase64Md5);
+        } finally {
+            FileUtil.deleteFile(tmpFile);
+        }
+    }
+
     /** Test that {@link FileUtil#recursiveSymlink(File, File)} properly simlink files. */
     public void testRecursiveSymlink() throws IOException {
         File dir1 = null;
diff --git a/tests/src/com/android/tradefed/util/GCSFileDownloaderFuncTest.java b/tests/src/com/android/tradefed/util/GCSFileDownloaderFuncTest.java
index a9a925c..327653b 100644
--- a/tests/src/com/android/tradefed/util/GCSFileDownloaderFuncTest.java
+++ b/tests/src/com/android/tradefed/util/GCSFileDownloaderFuncTest.java
@@ -18,6 +18,10 @@
 
 import com.android.tradefed.build.BuildRetrievalError;
 
+import com.google.cloud.storage.Blob;
+import com.google.cloud.storage.Bucket;
+import com.google.cloud.storage.Storage.BlobListOption;
+
 import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
@@ -42,22 +46,15 @@
     private static final String FOLDER_NAME1 = "folder1";
     private static final String FOLDER_NAME2 = "folder2";
     private static final String FILE_CONTENT = "Hello World!";
-    private static final long TIMEOUT = 30000L;
 
     private GCSFileDownloader mDownloader;
+    private Bucket mBucket;
     private String mRemoteRoot;
     private File mLocalRoot;
 
-    private static void createFile(String content, String bucketName, String... pathSegs)
-            throws IOException {
+    private static void createFile(String content, Bucket bucket, String... pathSegs) {
         String path = String.join("/", pathSegs);
-        getGCSBucketUtil(bucketName).pushString(content, Paths.get(path));
-    }
-
-    private static GCSBucketUtil getGCSBucketUtil(String bucketName) {
-        GCSBucketUtil bucket = new GCSBucketUtil(bucketName);
-        bucket.setTimeoutMs(TIMEOUT);
-        return bucket;
+        bucket.create(path, content.getBytes());
     }
 
     @Before
@@ -66,12 +63,6 @@
                 FileUtil.createTempFile(GCSFileDownloaderFuncTest.class.getSimpleName(), "");
         mRemoteRoot = tempFile.getName();
         FileUtil.deleteFile(tempFile);
-        createFile(FILE_CONTENT, BUCKET_NAME, mRemoteRoot, FILE_NAME1);
-        createFile(FILE_NAME2, BUCKET_NAME, mRemoteRoot, FOLDER_NAME1, FILE_NAME2);
-        createFile(FILE_NAME3, BUCKET_NAME, mRemoteRoot, FOLDER_NAME1, FILE_NAME3);
-        createFile(FILE_NAME4, BUCKET_NAME, mRemoteRoot, FOLDER_NAME1, FOLDER_NAME2, FILE_NAME4);
-
-        mLocalRoot = FileUtil.createTempDir(GCSFileDownloaderFuncTest.class.getSimpleName());
         mDownloader =
                 new GCSFileDownloader() {
 
@@ -88,14 +79,21 @@
                         }
                     }
                 };
+        mBucket = mDownloader.getStorage().get(BUCKET_NAME);
+        createFile(FILE_CONTENT, mBucket, mRemoteRoot, FILE_NAME1);
+        createFile(FILE_NAME2, mBucket, mRemoteRoot, FOLDER_NAME1, FILE_NAME2);
+        createFile(FILE_NAME3, mBucket, mRemoteRoot, FOLDER_NAME1, FILE_NAME3);
+        createFile(FILE_NAME4, mBucket, mRemoteRoot, FOLDER_NAME1, FOLDER_NAME2, FILE_NAME4);
+        mLocalRoot = FileUtil.createTempDir(GCSFileDownloaderFuncTest.class.getSimpleName());
+
     }
 
     @After
-    public void tearDown() throws IOException {
+    public void tearDown() {
         FileUtil.recursiveDelete(mLocalRoot);
-        GCSBucketUtil bucket = new GCSBucketUtil(BUCKET_NAME);
-        bucket.setTimeoutMs(TIMEOUT);
-        bucket.remove(mRemoteRoot, true);
+        for (Blob blob : mBucket.list(BlobListOption.prefix(mRemoteRoot)).iterateAll()) {
+            blob.delete();
+        }
     }
 
     @Test
@@ -126,10 +124,33 @@
     }
 
     @Test
+    public void testDownloadFile_nonExist() throws Exception {
+        try {
+            mDownloader.downloadFile(
+                    String.format("gs://%s/%s/%s", BUCKET_NAME, mRemoteRoot, "non_exist_file"));
+            Assert.fail("Should throw BuildRetrievalError.");
+        } catch (BuildRetrievalError e) {
+            // Expect BuildRetrievalError
+        }
+    }
+
+    @Test
     public void testDownloadFile_folder() throws Exception {
         File localFile =
                 mDownloader.downloadFile(
+                        String.format("gs://%s/%s/%s/", BUCKET_NAME, mRemoteRoot, FOLDER_NAME1));
+        checkDownloadedFolder(localFile);
+    }
+
+    @Test
+    public void testDownloadFile_folderNotsanitize() throws Exception {
+        File localFile =
+                mDownloader.downloadFile(
                         String.format("gs://%s/%s/%s", BUCKET_NAME, mRemoteRoot, FOLDER_NAME1));
+        checkDownloadedFolder(localFile);
+    }
+
+    private void checkDownloadedFolder(File localFile) throws Exception {
         Assert.assertTrue(localFile.isDirectory());
         Assert.assertEquals(3, localFile.list().length);
         for (String filename : localFile.list()) {
@@ -158,6 +179,17 @@
     }
 
     @Test
+    public void testDownloadFile_folder_nonExist() throws Exception {
+        try {
+            mDownloader.downloadFile(
+                    String.format("gs://%s/%s/%s/", BUCKET_NAME, "mRemoteRoot", "nonExistFolder"));
+            Assert.fail("Should throw BuildRetrievalError.");
+        } catch (BuildRetrievalError e) {
+            // Expect BuildRetrievalError
+        }
+    }
+
+    @Test
     public void testCheckFreshness() throws Exception {
         String remotePath = String.format("gs://%s/%s/%s", BUCKET_NAME, mRemoteRoot, FILE_NAME1);
         File localFile = mDownloader.downloadFile(remotePath);
@@ -169,7 +201,7 @@
         String remotePath = String.format("gs://%s/%s/%s", BUCKET_NAME, mRemoteRoot, FILE_NAME1);
         File localFile = mDownloader.downloadFile(remotePath);
         // Change the remote file.
-        createFile("New content.", BUCKET_NAME, mRemoteRoot, FILE_NAME1);
+        createFile("New content.", mBucket, mRemoteRoot, FILE_NAME1);
         Assert.assertFalse(mDownloader.isFresh(localFile, remotePath));
     }
 
@@ -184,8 +216,7 @@
     public void testCheckFreshness_folder_addFile() throws Exception {
         String remotePath = String.format("gs://%s/%s/%s", BUCKET_NAME, mRemoteRoot, FOLDER_NAME1);
         File localFolder = mDownloader.downloadFile(remotePath);
-        createFile(
-                "A new file", BUCKET_NAME, mRemoteRoot, FOLDER_NAME1, FOLDER_NAME2, "new_file.txt");
+        createFile("A new file", mBucket, mRemoteRoot, FOLDER_NAME1, FOLDER_NAME2, "new_file.txt");
         Assert.assertFalse(mDownloader.isFresh(localFolder, remotePath));
     }
 
@@ -193,8 +224,7 @@
     public void testCheckFreshness_folder_removeFile() throws Exception {
         String remotePath = String.format("gs://%s/%s/%s", BUCKET_NAME, mRemoteRoot, FOLDER_NAME1);
         File localFolder = mDownloader.downloadFile(remotePath);
-        getGCSBucketUtil(BUCKET_NAME)
-                .remove(Paths.get(mRemoteRoot, FOLDER_NAME1, FILE_NAME3), true);
+        mBucket.get(Paths.get(mRemoteRoot, FOLDER_NAME1, FILE_NAME3).toString()).delete();
         Assert.assertFalse(mDownloader.isFresh(localFolder, remotePath));
     }
 
@@ -202,7 +232,7 @@
     public void testCheckFreshness_folder_changeFile() throws Exception {
         String remotePath = String.format("gs://%s/%s/%s", BUCKET_NAME, mRemoteRoot, FOLDER_NAME1);
         File localFolder = mDownloader.downloadFile(remotePath);
-        createFile("New content", BUCKET_NAME, mRemoteRoot, FOLDER_NAME1, FILE_NAME3);
+        createFile("New content", mBucket, mRemoteRoot, FOLDER_NAME1, FILE_NAME3);
         Assert.assertFalse(mDownloader.isFresh(localFolder, remotePath));
     }
 }
diff --git a/tests/src/com/android/tradefed/util/GCSFileDownloaderTest.java b/tests/src/com/android/tradefed/util/GCSFileDownloaderTest.java
index 78dd1fb..54b4d8d 100644
--- a/tests/src/com/android/tradefed/util/GCSFileDownloaderTest.java
+++ b/tests/src/com/android/tradefed/util/GCSFileDownloaderTest.java
@@ -61,7 +61,7 @@
         try {
             localFile = mGCSFileDownloader.downloadFile("gs://bucket/this/is/a/file.txt");
             String content = FileUtil.readStringFromFile(localFile);
-            Assert.assertEquals("bucket\n/this/is/a/file.txt", content);
+            Assert.assertEquals("bucket\nthis/is/a/file.txt", content);
         } finally {
             FileUtil.deleteFile(localFile);
         }
@@ -91,7 +91,7 @@
     public void testParseGcsPath() throws Exception {
         String[] parts = mGCSFileDownloader.parseGcsPath("gs://bucketname/path/to/file");
         Assert.assertEquals("bucketname", parts[0]);
-        Assert.assertEquals("/path/to/file", parts[1]);
+        Assert.assertEquals("path/to/file", parts[1]);
     }
 
     @Test
@@ -100,7 +100,7 @@
         String gcsPath = "gs:/bucketName/path/to/file";
         String[] parts = mGCSFileDownloader.parseGcsPath(gcsPath);
         Assert.assertEquals("bucketName", parts[0]);
-        Assert.assertEquals("/path/to/file", parts[1]);
+        Assert.assertEquals("path/to/file", parts[1]);
     }
 
     @Test
diff --git a/tests/src/com/android/tradefed/util/StreamUtilTest.java b/tests/src/com/android/tradefed/util/StreamUtilTest.java
index 0bc4cce..f1a238c 100644
--- a/tests/src/com/android/tradefed/util/StreamUtilTest.java
+++ b/tests/src/com/android/tradefed/util/StreamUtilTest.java
@@ -17,7 +17,6 @@
 
 import com.android.tradefed.result.ByteArrayInputStreamSource;
 import com.android.tradefed.result.InputStreamSource;
-import com.android.tradefed.util.StreamUtil;
 
 import junit.framework.TestCase;
 
@@ -29,13 +28,12 @@
 import java.io.OutputStreamWriter;
 import java.io.Writer;
 
-/**
- * Unit tests for the {@link StreamUtil} utility class
- */
+/** Unit tests for the {@link com.android.tradefed.util.StreamUtil} utility class */
 public class StreamUtilTest extends TestCase {
 
     /**
-     * Verify that {@link StreamUtil#getByteArrayListFromSource} works as expected.
+     * Verify that {@link com.android.tradefed.util.StreamUtil#getByteArrayListFromSource} works as
+     * expected.
      */
     public void testGetByteArrayListFromSource() throws Exception {
         final String contents = "this is a string";
@@ -53,7 +51,8 @@
     }
 
     /**
-     * Verify that {@link StreamUtil#getByteArrayListFromStream} works as expected.
+     * Verify that {@link com.android.tradefed.util.StreamUtil#getByteArrayListFromStream} works as
+     * expected.
      */
     public void testGetByteArrayListFromStream() throws Exception {
         final String contents = "this is a string";
@@ -69,7 +68,8 @@
     }
 
     /**
-     * Verify that {@link StreamUtil#getStringFromSource} works as expected.
+     * Verify that {@link com.android.tradefed.util.StreamUtil#getStringFromSource} works as
+     * expected.
      */
     public void testGetStringFromSource() throws Exception {
         final String contents = "this is a string";
@@ -81,7 +81,8 @@
     }
 
     /**
-     * Verify that {@link StreamUtil#getBufferedReaderFromStreamSrc} works as expected.
+     * Verify that {@link com.android.tradefed.util.StreamUtil#getBufferedReaderFromStreamSrc} works
+     * as expected.
      */
     public void testGetBufferedReaderFromInputStream() throws Exception {
         final String contents = "this is a string";
@@ -97,7 +98,8 @@
     }
 
     /**
-     * Verify that {@link StreamUtil#countLinesFromSource} works as expected.
+     * Verify that {@link com.android.tradefed.util.StreamUtil#countLinesFromSource} works as
+     * expected.
      */
     public void testCountLinesFromSource() throws Exception {
         final String contents = "foo\nbar\n\foo\n";
@@ -106,7 +108,8 @@
     }
 
     /**
-     * Verify that {@link StreamUtil#getStringFromStream} works as expected.
+     * Verify that {@link com.android.tradefed.util.StreamUtil#getStringFromStream} works as
+     * expected.
      */
     public void testGetStringFromStream() throws Exception {
         final String contents = "this is a string";
@@ -116,7 +119,9 @@
     }
 
     /**
-     * Verify that {@link StreamUtil#calculateMd5(InputStream)} works as expected.
+     * Verify that {@link com.android.tradefed.util.StreamUtil#calculateMd5(InputStream)} works as
+     * expected.
+     *
      * @throws IOException
      */
     public void testCalculateMd5() throws IOException {
@@ -127,6 +132,20 @@
         assertEquals(md5, actualMd5);
     }
 
+    /**
+     * Verify that {@link com.android.tradefed.util.StreamUtil#calculateBase64Md5(InputStream)}
+     * works as expected.
+     *
+     * @throws IOException
+     */
+    public void testCalculateBase64Md5() throws IOException {
+        final String source = "testtesttesttesttest";
+        final String base64Md5 = "8xf2gvr+AwnGpCOvC076WQ==";
+        ByteArrayInputStream inputSource = new ByteArrayInputStream(source.getBytes());
+        String actualBase64Md5 = StreamUtil.calculateBase64Md5(inputSource);
+        assertEquals(base64Md5, actualBase64Md5);
+    }
+
     public void testCopyStreams() throws Exception {
         String text = getLargeText();
         ByteArrayInputStream bais = new ByteArrayInputStream(text.getBytes());