Cache/retrieve extracted CIPD packages in local isolate cache

client/tests/run_isolated_test.py

Index: client/tests/run_isolated_test.py
diff --git a/client/tests/run_isolated_test.py b/client/tests/run_isolated_test.py
index a58e1261721b8387ae6eeadfb469c68b11f4ec52..a24d0cc419e8cd7a6f861f6443fc0146c58f4c6d 100755
--- a/client/tests/run_isolated_test.py
+++ b/client/tests/run_isolated_test.py
@@ -428,7 +428,13 @@ class RunIsolatedTest(RunIsolatedTestBase):
         return 0
 
     self.popen_mocks.append(fake_ensure)
+    self._fake_isolated_cache = {}
+    self.mock(cipd.CipdClient, '_ensure_from_isolate',
+              self.fake_ensure_from_isolate)
+    self.mock(cipd.CipdClient, '_isolate_cipd', self.fake_isolate_cipd)
+
     cipd_cache = os.path.join(self.tempdir, 'cipd_cache')
+
     cmd = [
       '--no-log',
       '--cache', os.path.join(self.tempdir, 'cache'),
@@ -478,6 +484,16 @@ class RunIsolatedTest(RunIsolatedTestBase):
         echo_cmd[0])
     self.assertEqual(echo_cmd[1:], ['hello', 'world'])
 
+  def fake_ensure_from_isolate(self, target_dir, cipd_isolated, isolate_cache):
+    # Not seen first time, then seen all other times
+    if cipd_isolated not in self._fake_isolated_cache:
+      self._fake_isolated_cache[cipd_isolated] = True
+      return False
+    return True
+
+  def fake_isolate_cipd(self, root, pkgs, isolate_cache, cipd_cache):
+    pass
+
   def test_main_naked_with_cipd_client_no_packages(self):
     cipd_cache = os.path.join(self.tempdir, 'cipd_cache')
     cmd = [