diff --git a/tempest/tests/lib/cli/test_execute.py b/tempest/tests/lib/cli/test_execute.py
index b846c46..cc9c94c 100644
--- a/tempest/tests/lib/cli/test_execute.py
+++ b/tempest/tests/lib/cli/test_execute.py
@@ -12,26 +12,65 @@
 #    under the License.
 
 
+import mock
+import subprocess
+
 from tempest.lib.cli import base as cli_base
 from tempest.lib import exceptions
 from tempest.tests import base
 
 
 class TestExecute(base.TestCase):
-    def test_execute_success(self):
+
+    @mock.patch('subprocess.Popen', autospec=True)
+    def test_execute_success(self, mock_popen):
+        mock_popen.return_value.returncode = 0
+        mock_popen.return_value.communicate.return_value = (
+            "__init__.py", "")
         result = cli_base.execute("/bin/ls", action="tempest",
                                   flags="-l -a")
+        args, kwargs = mock_popen.call_args
+        # Check merge_stderr == False
+        self.assertEqual(subprocess.PIPE, kwargs['stderr'])
+        # Check action and flags are passed
+        args = args[0]
+        # We just tests that all pieces are passed through, we cannot make
+        # assumptions about the order
+        self.assertIn("/bin/ls", args)
+        self.assertIn("-l", args)
+        self.assertIn("-a", args)
+        self.assertIn("tempest", args)
+        # The result is mocked - checking that the mock was invoked correctly
         self.assertIsInstance(result, str)
         self.assertIn("__init__.py", result)
 
-    def test_execute_failure(self):
+    @mock.patch('subprocess.Popen', autospec=True)
+    def test_execute_failure(self, mock_popen):
+        mock_popen.return_value.returncode = 1
+        mock_popen.return_value.communicate.return_value = (
+            "No such option --foobar", "")
         result = cli_base.execute("/bin/ls", action="tempest.lib",
                                   flags="--foobar", merge_stderr=True,
                                   fail_ok=True)
+        args, kwargs = mock_popen.call_args
+        # Check the merge_stderr
+        self.assertEqual(subprocess.STDOUT, kwargs['stderr'])
+        # Check action and flags are passed
+        args = args[0]
+        # We just tests that all pieces are passed through, we cannot make
+        # assumptions about the order
+        self.assertIn("/bin/ls", args)
+        self.assertIn("--foobar", args)
+        self.assertIn("tempest.lib", args)
+        # The result is mocked - checking that the mock was invoked correctly
         self.assertIsInstance(result, str)
         self.assertIn("--foobar", result)
 
-    def test_execute_failure_raise_exception(self):
+    @mock.patch('subprocess.Popen', autospec=True)
+    def test_execute_failure_raise_exception(self, mock_popen):
+        mock_popen.return_value.returncode = 1
+        mock_popen.return_value.communicate.return_value = (
+            "No such option --foobar", "")
         self.assertRaises(exceptions.CommandFailed, cli_base.execute,
                           "/bin/ls", action="tempest", flags="--foobar",
                           merge_stderr=True)