public MastershipInfo mastershipInfo() {
        return mastershipInfo;
    }
@Test
    public void checkConstruction() {
        assertThat(event1.type(), is(MastershipEvent.Type.BACKUPS_CHANGED));
        assertThat(event1.subject(), is(deviceId1));
        assertThat(event1.mastershipInfo(), is(mastershipInfo1));

        assertThat(event4.time(), is(time));
        assertThat(event4.type(), is(MastershipEvent.Type.MASTER_CHANGED));
        assertThat(event4.subject(), is(deviceId1));
        assertThat(event4.mastershipInfo(), is(mastershipInfo2));
    }