diff --git a/paasta_tools/marathon_tools.py b/paasta_tools/marathon_tools.py
index 904adeb804..395c9f9ca1 100644
--- a/paasta_tools/marathon_tools.py
+++ b/paasta_tools/marathon_tools.py
@@ -184,7 +184,13 @@ def __repr__(self):
         )
 
     def copy(self):
-        return self.__class__(self.service, self.instance, dict(self.config_dict), dict(self.branch_dict))
+        return self.__class__(
+            service=self.service,
+            instance=self.instance,
+            cluster=self.cluster,
+            config_dict=dict(self.config_dict),
+            branch_dict=dict(self.branch_dict),
+        )
 
     def get_min_instances(self):
         return self.config_dict.get('min_instances', 1)
@@ -703,8 +709,6 @@ def get_proxy_port_for_instance(name, instance, cluster=None, soa_dir=DEFAULT_SO
     :param cluster: The cluster to read the configuration for
     :param soa_dir: The SOA config directory to read from
     :returns: The proxy_port for the service instance, or None if not defined"""
-    if not cluster:
-        cluster = load_system_paasta_config().get_cluster()
     namespace = read_namespace_for_service_instance(name, instance, cluster, soa_dir)
     nerve_dict = load_service_namespace_config(name, namespace, soa_dir)
     return nerve_dict.get('proxy_port')
diff --git a/tests/test_marathon_tools.py b/tests/test_marathon_tools.py
index 1e20a851da..c21f92ea26 100644
--- a/tests/test_marathon_tools.py
+++ b/tests/test_marathon_tools.py
@@ -2159,3 +2159,68 @@ def test_create_complete_config():
     ):
         marathon_tools.create_complete_config('service', 'instance', soa_dir=mock.Mock())
         mock_format_marathon_app_dict.assert_called_once_with()
+
+
+def test_marathon_config_key_errors():
+    fake_marathon_config = marathon_tools.MarathonConfig({}, '')
+    with raises(marathon_tools.MarathonNotConfigured):
+        fake_marathon_config.get_url()
+    with raises(marathon_tools.MarathonNotConfigured):
+        fake_marathon_config.get_username()
+    with raises(marathon_tools.MarathonNotConfigured):
+        fake_marathon_config.get_password()
+
+
+def test_marathon_service_config_copy():
+    fake_marathon_service_config = marathon_tools.MarathonServiceConfig(
+        service='fake-service',
+        instance='fake-instance',
+        cluster='fake-cluster',
+        config_dict={'elem': 'test'},
+        branch_dict={'elem2': 'test2'},
+    )
+    fake_marathon_service_config_2 = fake_marathon_service_config.copy()
+    assert fake_marathon_service_config is not fake_marathon_service_config_2
+    assert fake_marathon_service_config == fake_marathon_service_config_2
+
+
+def test_marathon_service_config_get_healthchecks_invalid_type():
+    fake_marathon_service_config = marathon_tools.MarathonServiceConfig(
+        service='fake-service',
+        instance='fake-instance',
+        cluster='fake-cluster',
+        config_dict={},
+        branch_dict={},
+    )
+    with mock.patch.object(marathon_tools.MarathonServiceConfig, 'get_healthcheck_mode', autospec=True,
+                           return_value='fake-mode'):
+        with raises(marathon_tools.InvalidMarathonHealthcheckMode):
+            fake_marathon_service_config.get_healthchecks(mock.Mock())
+
+
+def test_marathon_service_config_get_desired_state_human_invalid_desired_state():
+    fake_marathon_service_config = marathon_tools.MarathonServiceConfig(
+        service='fake-service',
+        instance='fake-instance',
+        cluster='fake-cluster',
+        config_dict={},
+        branch_dict={},
+    )
+    with mock.patch.object(marathon_tools.MarathonServiceConfig, 'get_desired_state', autospec=True,
+                           return_value='fake-state'):
+        assert 'Unknown (desired_state: fake-state)' in fake_marathon_service_config.get_desired_state_human()
+
+
+def test_read_namespace_for_service_instance_no_cluster():
+    mock_get_cluster = mock.Mock()
+    with contextlib.nested(
+            mock.patch('paasta_tools.marathon_tools.service_configuration_lib.read_extra_service_information',
+                       autospec=True),
+            mock.patch('paasta_tools.marathon_tools.load_system_paasta_config', autospec=True,
+                       return_value=mock.Mock(get_cluster=mock_get_cluster)),
+    ) as (
+        _,
+        _,
+    ):
+        marathon_tools.read_namespace_for_service_instance(mock.Mock(), mock.Mock())
+        mock_get_cluster.assert_called_once_with()