public static String getDefaultKeyDirectory() {
        return getDefaultKeyDirectory(System.getProperty("os.name"));
    }
@Test
    public void testGetDefaultKeyDirectory() {
        assertTrue(
                WalletUtils.getDefaultKeyDirectory("Mac OS X")
                        .endsWith(
                                String.format(
                                        "%sLibrary%sEthereum", File.separator, File.separator)));
        assertTrue(
                WalletUtils.getDefaultKeyDirectory("Windows")
                        .endsWith(String.format("%sEthereum", File.separator)));
        assertTrue(
                WalletUtils.getDefaultKeyDirectory("Linux")
                        .endsWith(String.format("%s.ethereum", File.separator)));
    }