update test

Author: FumingZhang

src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_aks_commands.py

@@ -6621,6 +6621,17 @@ def test_aks_automatic_sku(self, resource_group, resource_group_location):
             ],
         )
 
+        # get-credentials
+        fd, temp_path = tempfile.mkstemp()
+        self.kwargs.update({'file': temp_path})
+        try:
+            self.cmd(
+                'aks get-credentials -g {resource_group} -n {name} --file "{file}"')
+            self.assertGreater(os.path.getsize(temp_path), 0)
+        finally:
+            os.close(fd)
+            os.remove(temp_path)
+
         # scale the cluster
         scale_cluster_cmd = (
             "aks scale --resource-group={resource_group} --name={name} "