Improve Test Coverage for Kubernetes Executor (apache#15617)

According to the current stats of codecov.io assessment of the Airflow code base, the test coverage for
the kubernetes_executor.py module is about 63%. This metric definitely
needs to be improved upon.

This PR addresses the unit test coverage for the delete_pod method in the AirflowKubernetesScheduler class in the kubernetes_executor.py module. And when merged will help to improve the test coverage metric.

fixes part of apache#15523

tests/executors/test_kubernetes_executor.py

@@ -25,14 +25,13 @@
 
 import pytest
 from kubernetes.client import models as k8s
+from kubernetes.client.rest import ApiException
 from urllib3 import HTTPResponse
 
 from airflow.utils import timezone
 from tests.test_utils.config import conf_vars
 
 try:
-    from kubernetes.client.rest import ApiException
-
     from airflow.executors.kubernetes_executor import (
         AirflowKubernetesScheduler,
         KubernetesExecutor,
@@ -120,6 +119,71 @@ def test_execution_date_serialize_deserialize(self):
 
         assert datetime_obj == new_datetime_obj
 
+    @unittest.skipIf(AirflowKubernetesScheduler is None, 'kubernetes python package is not installed')
+    @mock.patch('airflow.executors.kubernetes_executor.get_kube_client')
+    @mock.patch('airflow.executors.kubernetes_executor.client')
+    @mock.patch('airflow.executors.kubernetes_executor.KubernetesJobWatcher')
+    def test_delete_pod_successfully(
+        self, mock_watcher, mock_client, mock_kube_client
+    ):  # pylint: disable=unused-argument
+        pod_id = "my-pod-1"
+        namespace = "my-namespace-1"
+
+        mock_delete_namespace = mock.MagicMock()
+        mock_kube_client.return_value.delete_namespaced_pod = mock_delete_namespace
+
+        kube_executor = KubernetesExecutor()
+        kube_executor.job_id = "test-job-id"
+        kube_executor.start()
+        kube_executor.kube_scheduler.delete_pod(pod_id, namespace)
+
+        mock_delete_namespace.assert_called_with(pod_id, namespace, body=mock_client.V1DeleteOptions())
+
+    @unittest.skipIf(AirflowKubernetesScheduler is None, 'kubernetes python package is not installed')
+    @mock.patch('airflow.executors.kubernetes_executor.get_kube_client')
+    @mock.patch('airflow.executors.kubernetes_executor.client')
+    @mock.patch('airflow.executors.kubernetes_executor.KubernetesJobWatcher')
+    def test_delete_pod_raises_404(
+        self, mock_watcher, mock_client, mock_kube_client
+    ):  # pylint: disable=unused-argument
+        pod_id = "my-pod-1"
+        namespace = "my-namespace-2"
+
+        mock_delete_namespace = mock.MagicMock()
+        mock_kube_client.return_value.delete_namespaced_pod = mock_delete_namespace
+
+        # ApiException is raised because status is not 404
+        mock_kube_client.return_value.delete_namespaced_pod.side_effect = ApiException(status=400)
+        kube_executor = KubernetesExecutor()
+        kube_executor.job_id = "test-job-id"
+        kube_executor.start()
+
+        with pytest.raises(ApiException):
+            kube_executor.kube_scheduler.delete_pod(pod_id, namespace)
+            mock_delete_namespace.assert_called_with(pod_id, namespace, body=mock_client.V1DeleteOptions())
+
+    @unittest.skipIf(AirflowKubernetesScheduler is None, 'kubernetes python package is not installed')
+    @mock.patch('airflow.executors.kubernetes_executor.get_kube_client')
+    @mock.patch('airflow.executors.kubernetes_executor.client')
+    @mock.patch('airflow.executors.kubernetes_executor.KubernetesJobWatcher')
+    def test_delete_pod_404_not_raised(
+        self, mock_watcher, mock_client, mock_kube_client
+    ):  # pylint: disable=unused-argument
+        pod_id = "my-pod-1"
+        namespace = "my-namespace-3"
+
+        mock_delete_namespace = mock.MagicMock()
+        mock_kube_client.return_value.delete_namespaced_pod = mock_delete_namespace
+
+        # ApiException not raised because the status is 404
+        mock_kube_client.return_value.delete_namespaced_pod.side_effect = ApiException(status=404)
+        kube_executor = KubernetesExecutor()
+        kube_executor.job_id = "test-job-id"
+        kube_executor.start()
+
+        kube_executor.kube_scheduler.delete_pod(pod_id, namespace)
+        mock_delete_namespace.assert_called_with(pod_id, namespace, body=mock_client.V1DeleteOptions())
+
 
 class TestKubernetesExecutor(unittest.TestCase):
     """
@@ -160,7 +224,6 @@ def test_run_next_exception(self, mock_get_kube_client, mock_kubernetes_job_watc
             ('kubernetes', 'pod_template_file'): path,
         }
         with conf_vars(config):
-
             kubernetes_executor = self.kubernetes_executor
             kubernetes_executor.start()
             # Execute a task while the Api Throws errors