DefaultBootLogger implements BootLogger { @Override public void stderr(String message) { stderr.println(message); } DefaultBootLogger(boolean trace);  DefaultBootLogger(boolean trace, PrintStream stdout, PrintStream stderr); @Override void trace(Supplier<String> messageSupplier); @Override void stdout(String message); @Override void stderr(String message); @Override void stderr(String message, Throwable th);  }
@Test public void testStderr() { DefaultBootLogger logger = new DefaultBootLogger(true, mockStdout, mockStderr); logger.stderr("errmsg"); verify(mockStderr).println("errmsg"); verifyZeroInteractions(mockStdout); }