@Test
public final void testWriteFileContentToResponseShouldWriteErrorMessageWhenPathIsAnInvalidFileName() throws IOException {

    // GIVEN
    given(messageFileReader.readFile("invalidfilename", path)).willReturn(null);
    // WHEN
    underTest.writeFileContentToResponse(request, response, "invalidfilename", path);
    // THEN
    verify(response).setContentType("text/html");
    verify(printWriter).write("Requested file not found.");
    verify(printWriter).flush();
    verify(printWriter).close();
}