remove stale test data on the device

build/android/pylib/device/device_utils_test.py

Index: build/android/pylib/device/device_utils_test.py
diff --git a/build/android/pylib/device/device_utils_test.py b/build/android/pylib/device/device_utils_test.py
index e395c8f33d36081a9b1c20a7182fa73a159ea4ca..76e10e42416771f34ddfc2c1624e7b07f17188f0 100755
--- a/build/android/pylib/device/device_utils_test.py
+++ b/build/android/pylib/device/device_utils_test.py
@@ -1144,6 +1144,25 @@ class DeviceUtilsPushChangedFilesZippedTest(DeviceUtilsTest):
         [('/test/host/path/file1', '/test/device/path/file1'),
          ('/test/host/path/file2', '/test/device/path/file2')])
 
+class DeviceUtilsDeleteStaleFilesTest(DeviceUtilsTest):
+
+  def testDeleteStaleFiles_emtpy(self):
+    files = []
+    with self.assertCalls():
+      self.device._DeleteStaleFiles(files)
+
+  def testDeleteStaleFiles_single(self):
+    files = ['/test/device/path/file1']
+    with self.assertCalls((self.call.adb.Shell(
+        'rm /test/device/path/file1'), '')):
+      self.device._DeleteStaleFiles(files)
+
+  def testDeleteStaleFiles_multiple(self):
+    files = ['/test/device/path/file1', '/test/device/path/file2']
+    with self.assertCalls(
+        (self.call.adb.Shell('rm /test/device/path/file1'), ''),
+        (self.call.adb.Shell('rm /test/device/path/file2'), '')):
+      self.device._DeleteStaleFiles(files)
 
 class DeviceUtilsFileExistsTest(DeviceUtilsTest):