StefMa @Medium - Developers, please write tests!

MyClock.java

public class MyClock {

    public String getCurrentTime(TimeFormat format) {
        switch (format) {
            case GERMAN:
                return getStringFormattedTimeWithPatternAndLocale("HH:mm 'Uhr'", Locale.GERMANY);
            case AMERICAN:
                return getStringFormattedTimeWithPatternAndLocale("hh:mm a", Locale.US);
            case GERMAN_WITH_DATE:
                return getStringFormattedTimeWithPatternAndLocale("HH:mm 'Uhr,' EEEE dd.MM.yyyy", Locale.GERMANY);
            case AMERICAN_WITH_DATE:
                return getStringFormattedTimeWithPatternAndLocale("hh:mm a',' EEEE MM.dd.yyyy", Locale.US);
            default:
                return "";
        }
    }

    @VisibleForTesting
    long currentTimeMillis() {
        return System.currentTimeMillis();
    }

    private String getStringFormattedTimeWithPatternAndLocale(String pattern, Locale locale) {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat(pattern, locale);
        Date currentDate = new Date(currentTimeMillis());
        return simpleDateFormat.format(currentDate);
    }

}

MyClockTest.java

public class MyClockTest {

    private MyClock mMyClock;

    private long mTimeMillis = System.currentTimeMillis();

    @Before
    public void setUp() throws Exception {
        mMyClock = new MyClock() {
            long currentTimeMillis() {
                return mTimeMillis;
            }
        };
    }

    @Test
    public void testGetCurrentName_ShouldReturnTimeInGermanFormat() throws Exception {
        String germanTime = mMyClock.getCurrentTime(TimeFormat.GERMAN);

        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("HH:mm 'Uhr'", Locale.GERMANY);
        String formattedTime = simpleDateFormat.format(new Date(mTimeMillis));
        assertThat(germanTime, is(equalTo(formattedTime)));
    }

    @Test
    public void testGetCurrentName_ShouldReturnTimeInAmericanFormat() throws Exception {
        String americanTime = mMyClock.getCurrentTime(TimeFormat.AMERICAN);

        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("hh:mm a", Locale.US);
        String formattedTime = simpleDateFormat.format(new Date(mTimeMillis));
        assertThat(americanTime, is(equalTo(formattedTime)));
    }

    @Test
    public void testGetCurrentName_ShouldReturnTimeInGermanFormatWithDate() throws Exception {
        String americanTime = mMyClock.getCurrentTime(TimeFormat.GERMAN_WITH_DATE);

        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("HH:mm 'Uhr,' EEEE dd.MM.yyyy", Locale.GERMANY);
        String formattedTime = simpleDateFormat.format(new Date(mTimeMillis));
        assertThat(americanTime, is(equalTo(formattedTime)));
    }

    @Test
    public void testGetCurrentName_ShouldReturnTimeInAmericanFormatWithDate() throws Exception {
        String americanTime = mMyClock.getCurrentTime(TimeFormat.AMERICAN_WITH_DATE);

        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("hh:mm a',' EEEE MM.dd.yyyy", Locale.US);
        String formattedTime = simpleDateFormat.format(new Date(mTimeMillis));
        assertThat(americanTime, is(equalTo(formattedTime)));
    }

    @Test
    public void testCurrentTimeMillis_ShouldReturnCurrentTimeMillis() throws Exception {
        long clockTime = mMyClock.currentTimeMillis();

        assertThat(mTimeMillis, is(equalTo(clockTime)));
    }
}

TimeFormat.java

public enum TimeFormat {
    GERMAN, AMERICAN, GERMAN_WITH_DATE, AMERICAN_WITH_DATE
}