@Test
public void doLog_format_arguments_enabled_args_null() throws Exception {

    when(underlyingLogger.isWarnEnabled(testMarker)).thenReturn(true);
    lambdaLogger.doLog(testMarker, Level.WARN, "message format", null, testException);
    verify(underlyingLogger, times(1)).warn(eq(testMarker), eq("message format"), eq(testException));
}