long s = 1000;
long m = 60 * s;
long h = 60 * m;
TimeFormatter timeFormatter = new TimeFormatter();
assertThat(timeFormatter.formatMillis(0), equalTo("00:00:00.000"));
assertThat(timeFormatter.formatMillis(1), equalTo("00:00:00.001"));
assertThat(timeFormatter.formatMillis(10), equalTo("00:00:00.010"));
assertThat(timeFormatter.formatMillis(100), equalTo("00:00:00.100"));
assertThat(timeFormatter.formatMillis(2*s+1), equalTo("00:00:02.001"));
assertThat(timeFormatter.formatMillis(3*m+20*s+1), equalTo("00:03:20.001"));
assertThat(timeFormatter.formatMillis(44*h+33*m+22*s+1), equalTo("44:33:22.001"));