Log { public void error(String format, Object... args) { String s = String.format(format, args); errPrintln(s); }  void setVerbose(boolean verbose); void debug(String format, Object... args); void info(String format, Object... args); void error(String format, Object... args); void exception(Throwable t, String format, Object... args);  }
@Test public void testError() { assertEquals("", mLog.getOut()); assertEquals("", mLog.getErr()); mLog.error("Test %d", 44); assertEquals("", mLog.getOut()); assertEquals("Test 44\n", mLog.getErr()); }