@Test
public void testSetExceptionCode_exception_code_is_null() {

    FlashMap flashMap = new FlashMap();
    mockRequest.setAttribute(DispatcherServlet.OUTPUT_FLASH_MAP_ATTRIBUTE,
            flashMap);
    SystemException occurException = new SystemException(null, "message");
    testTarget.setExceptionCode(occurException, mockRequest, mockResponse);
    Enumeration<String> attributeNames = mockRequest.getAttributeNames();
    assertThat(attributeNames.nextElement().equals(
            DispatcherServlet.OUTPUT_FLASH_MAP_ATTRIBUTE), is(true));
    assertThat(attributeNames.hasMoreElements(), is(false));
    assertThat(mockResponse.getHeaderNames().isEmpty(), is(true));
    assertThat(flashMap.isEmpty(), is(true));
}