@Test
    public void testGetUserPermissionByTokenNull() {
        when(mockPermissionService.getPermissionMenu("namespaceId")).thenReturn(null);
        final ShenyuAdminResult result = permissionController.getUserPermissionByToken("token", "namespaceId");
        assertThat(result.getCode(), is(CommonErrorCode.ERROR));
        assertThat(result.getMessage(), is(ShenyuResultMessage.MENU_FAILED));
    }
add test case for {@link PermissionController}.
shenyu-admin/src/test/java/org/apache/shenyu/admin/controller/PermissionControllerTest.java