Refactor test_server functional tests

* Launching services with 0 workers makes no sense and would soon
  be prohibited in oslo.service. Passing workers=1 means that a
  service will be run in a current process.
* Extract the dummy _check_active method to the base class.

Change-Id: Ib687bf1b321845098e0564ada46e68a7850b01c6

neutron/tests/functional/test_server.py

@@ -46,7 +46,7 @@ class TestNeutronServer(base.BaseTestCase):
         self.service_pid = None
         self.workers = None
         self.temp_file = self.get_temp_file_path("test_server.tmp")
-        self.health_checker = None
+        self.health_checker = self._check_active
         self.pipein, self.pipeout = os.pipe()
         self.addCleanup(self._destroy_workers)
 
@@ -82,7 +82,9 @@ class TestNeutronServer(base.BaseTestCase):
 
         self.service_pid = pid
 
-        if self.workers > 0:
+        # If number of workers is 1 it is assumed that we run
+        # a service in the current process.
+        if self.workers > 1:
             # Wait at most 10 seconds to spawn workers
             condition = lambda: self.workers == len(self._get_workers())
 
@@ -111,18 +113,23 @@ class TestNeutronServer(base.BaseTestCase):
             except psutil.NoSuchProcess:
                 return None
 
-        if self.workers > 0:
+        if self.workers > 1:
             return [proc.pid for proc in psutil.process_iter()
                     if safe_ppid(proc) == self.service_pid]
         else:
             return [proc.pid for proc in psutil.process_iter()
                     if proc.pid == self.service_pid]
 
+    def _check_active(self):
+        """Dummy service activity check."""
+        time.sleep(5)
+        return True
+
     def _fake_start(self):
         with open(self.temp_file, 'a') as f:
             f.write(FAKE_START_MSG)
 
-    def _test_restart_service_on_sighup(self, service, workers=0):
+    def _test_restart_service_on_sighup(self, service, workers=1):
         """Test that a service correctly (re)starts on receiving SIGHUP.
 
         1. Start a service with a given number of workers.
@@ -188,7 +195,7 @@ class TestWsgiServer(TestNeutronServer):
         except socket.error:
             return False
 
-    def _run_wsgi(self, workers=0):
+    def _run_wsgi(self, workers=1):
         """Start WSGI server with a test application."""
 
         # Mock start method to check that children are started again on
@@ -220,13 +227,8 @@ class TestRPCServer(TestNeutronServer):
         self._plugin_patcher = mock.patch(TARGET_PLUGIN, autospec=True)
         self.plugin = self._plugin_patcher.start()
         self.plugin.return_value.rpc_workers_supported = True
-        self.health_checker = self._check_active
 
-    def _check_active(self):
-        time.sleep(5)
-        return True
-
-    def _serve_rpc(self, workers=0):
+    def _serve_rpc(self, workers=1):
         """Start RPC server with a given number of workers."""
 
         # Mock start method to check that children are started again on
@@ -259,7 +261,7 @@ class TestPluginWorker(TestNeutronServer):
         self._plugin_patcher = mock.patch(TARGET_PLUGIN, autospec=True)
         self.plugin = self._plugin_patcher.start()
 
-    def _start_plugin(self, workers=0):
+    def _start_plugin(self, workers=1):
         with mock.patch('neutron.manager.NeutronManager.get_plugin') as gp:
             gp.return_value = self.plugin
             launchers = service.start_plugin_workers()