It's was hard but i have finally a beginning of test for start VPCS

tests/api/test_version.py

@@ -52,7 +52,7 @@ def test_version_invalid_input_schema(server):
 
 
 @asyncio_patch("gns3server.handlers.version_handler.VersionHandler", return_value={})
-def test_version_invalid_output_schema():
+def test_version_invalid_output_schema(server):
     query = {'version': "0.4.2"}
     response = server.post('/version', query)
     assert response.status == 400

tests/api/test_vpcs.py

@@ -21,7 +21,7 @@ from gns3server import modules
 
 
 @asyncio_patch('gns3server.modules.VPCS.create_vm', return_value=84)
-def test_vpcs_create(server, mock):
+def test_vpcs_create(server):
     response = server.post('/vpcs', {'name': 'PC TEST 1'}, example=False)
     assert response.status == 200
     assert response.route == '/vpcs'

tests/modules/vpcs/test_vpcs_device.py

@@ -16,7 +16,13 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import pytest
-from unittest.mock import patch
+import asyncio
+from tests.utils import asyncio_patch
+
+#Move loop to util
+from tests.api.base import loop
+from asyncio.subprocess import Process
+from unittest.mock import patch, Mock
 from gns3server.modules.vpcs.vpcs_device import VPCSDevice
 from gns3server.modules.vpcs.vpcs_error import VPCSError
 
@@ -39,3 +45,9 @@ def test_vm_invalid_vpcs_path(tmpdir):
         assert vm.name == "test"
         assert vm.id == 42
 
+def test_start(tmpdir, loop):
+    with asyncio_patch("asyncio.create_subprocess_exec", return_value=Mock()):
+        vm = VPCSDevice("test", 42, working_dir=str(tmpdir), path="/bin/test_fake")
+        loop.run_until_complete(asyncio.async(vm.start()))
+        assert vm.is_running() == True
+

tests/utils.py

@@ -19,15 +19,43 @@ import asyncio
 from unittest.mock import patch
 
 
-def asyncio_patch(function, *args, **kwargs):
-    @asyncio.coroutine
-    def fake_anwser(*a, **kw):
-        return kwargs["return_value"]
+class _asyncio_patch:
+    """
+    A wrapper around python patch supporting asyncio.
+    Like the original patch you can use it as context
+    manager (with) or decorator
 
-    def register(func):
-        @patch(function, return_value=fake_anwser)
+    The original patch source code is the main source of
+    inspiration:
+    https://hg.python.org/cpython/file/3.4/Lib/unittest/mock.py
+    """
+    def __init__(self, function, *args, **kwargs):
+        self.function = function
+        self.args = args
+        self.kwargs = kwargs
+
+    def __enter__(self):
+        """Used when enter in the with block"""
+        self._patcher = patch(self.function, return_value=self._fake_anwser())
+        self._patcher.start()
+
+    def __exit__(self, *exc_info):
+        """Used when leaving the with block"""
+        self._patcher.stop()
+
+    def __call__(self, func, *args, **kwargs):
+        """Call is used when asyncio_patch is used as decorator"""
+        @patch(self.function, return_value=self._fake_anwser())
         @asyncio.coroutine
         def inner(*a, **kw):
             return func(*a, **kw)
         return inner
-    return register
+
+    def _fake_anwser(self):
+        future = asyncio.Future()
+        future.set_result(self.kwargs["return_value"])
+        return future
+
+
+def asyncio_patch(function, *args, **kwargs):
+    return _asyncio_patch(function, *args, **kwargs)