added logic to help provide dependent service ordering

daemon/tests/test_services.py

@@ -1,18 +1,94 @@
 import os
 
+import pytest
+
+from core.service import CoreService
 from core.service import ServiceManager
 
 _PATH = os.path.abspath(os.path.dirname(__file__))
 _SERVICES_PATH = os.path.join(_PATH, "myservices")
 
 
+class ServiceA(CoreService):
+    name = "A"
+    dependencies = ("B",)
+
+
+class ServiceB(CoreService):
+    name = "B"
+    dependencies = ("C",)
+
+
+class ServiceC(CoreService):
+    name = "C"
+    dependencies = ()
+
+
+class ServiceD(CoreService):
+    name = "D"
+    dependencies = ("A",)
+
+
+class ServiceE(CoreService):
+    name = "E"
+    dependencies = ("Z",)
+
+
+class ServiceF(CoreService):
+    name = "F"
+    dependencies = ()
+
+
 class TestServices:
-    def test_import_service(self):
+    def test_service_import(self):
         """
         Test importing a custom service.
-
-        :param conftest.Core core: core fixture to test with
         """
         ServiceManager.add_services(_SERVICES_PATH)
         assert ServiceManager.get("MyService")
         assert ServiceManager.get("MyService2")
+
+    def test_services_dependencies(self, session):
+        # given
+        services = [
+            ServiceA(),
+            ServiceB(),
+            ServiceC(),
+            ServiceD(),
+            ServiceF(),
+        ]
+
+        # when
+        startups = session.services.get_service_startups(services)
+
+        # then
+        assert len(startups) == 2
+
+    def test_services_dependencies_not_present(self, session):
+        # given
+        services = [
+            ServiceA(),
+            ServiceB(),
+            ServiceC(),
+            ServiceE()
+        ]
+
+        # when
+        with pytest.raises(ValueError):
+            session.services.get_service_startups(services)
+
+    def test_services_dependencies_cycle(self, session):
+        # given
+        service_c = ServiceC()
+        service_c.dependencies = ("D",)
+        services = [
+            ServiceA(),
+            ServiceB(),
+            service_c,
+            ServiceD(),
+            ServiceF()
+        ]
+
+        # when
+        with pytest.raises(ValueError):
+            session.services.get_service_startups(services)