app: Introduce API to return a list of all apps

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/app.py

@@ -49,6 +49,11 @@ class App:
         """Return an app with given ID."""
         return cls._all_apps[app_id]
 
+    @classmethod
+    def list(cls):
+        """Return a list of all apps."""
+        return cls._all_apps.values()
+
     def add(self, component):
         """Add a component to an app."""
         self.components[component.component_id] = component

plinth/tests/test_app.py

@@ -62,12 +62,18 @@ def test_app_instantiation():
     assert len(app._all_apps) == 1
 
 
-def test_get():
+def test_app_get():
     """Test that an app can be correctly retrieved."""
     app = AppTest()
     assert App.get(app.app_id) == app
 
 
+def test_app_list():
+    """Test listing all apps."""
+    app = AppTest()
+    assert list(App.list()) == [app]
+
+
 def test_app_add():
     """Test adding a components to an App."""
     app = AppTest()