Created
September 10, 2024 12:07
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dummy Java Clock mock to timetravel in unit tests
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| import java.time.Clock; | |
| import java.time.Duration; | |
| import java.time.Instant; | |
| import java.time.ZoneId; | |
| import java.time.temporal.ChronoUnit; | |
| /** Clock used so we can shift time in tests. */ | |
| public class MockClock extends Clock { | |
| private final Instant instant; | |
| private Duration shift; | |
| public MockClock() { | |
| this(Instant.now().truncatedTo(ChronoUnit.HOURS)); | |
| } | |
| public MockClock(Instant base) { | |
| this.instant = base; | |
| this.shift = Duration.ZERO; | |
| } | |
| public synchronized void shiftAbsolute(Duration shift) { | |
| assert shift != null; | |
| this.shift = shift; | |
| } | |
| public synchronized void shiftRelative(Duration shift) { | |
| assert shift != null; | |
| this.shift = this.shift.plus(shift); | |
| } | |
| @Override | |
| public ZoneId getZone() { | |
| return ZoneId.systemDefault(); | |
| } | |
| @Override | |
| public Clock withZone(ZoneId zone) { | |
| return new MockClock(instant); | |
| } | |
| @Override | |
| public Instant instant() { | |
| return instant.plus(shift); | |
| } | |
| } |
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| class MyTest { | |
| private MockClock clock; | |
| private MyObjectThatUseClock other; | |
| @BeforeEach | |
| void setUp() { | |
| clock = new MockClock(); | |
| other = new MyObjectThatUseClock(clock); | |
| } | |
| @Test | |
| void should_work() { | |
| assertThat(other.getState()).isEqualTo(State.INITIALIZING); | |
| clock.shiftAbsolute(Duration.ofSeconds(9)); | |
| other.recomputeState(); | |
| assertThat(other.getState()).isEqualTo(State.INITIALIZING); | |
| clock.shiftAbsolute(Duration.ofSeconds(11)); | |
| other.recomputeState(); | |
| assertThat(other.getState()).isEqualTo(State.PROCESSING); | |
| } | |
| } |
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