JarCastingFakeTime for Java
FakeTime uses a native Java agent to replace
System.currentTimeMillis()implementation with the one you can control using system properties.
Inspired by arvindsv/faketime.
public class ExamRegistrationServiceTest implements FakeTimeMixin {
@Autowired
ExamRegistrationService examRegistrationService;
@Test
public void registrationExpiresAfterGivenPeriod() {
ExamRegistration registration = examRegistrationService.openRegistrationValidFor(Duration.ofDays(5));
offsetRealTimeByDays(5);
assertThat(registration.hasExpired()).isTrue();
}
@Test
public void registrationIsValidDuringGivenPeriod() {
ExamRegistration registration = examRegistrationService.openRegistrationValidFor(Duration.ofDays(5));
offsetRealTimeBy(Duration.ofDays(5).minusMinutes(1));
assertThat(registration.hasExpired()).isFalse();
}
@After
public void restoreRealTimeAfterTest() {
restoreRealTime();
}
}
Manual setup
Start faking time in 4 easy steps:
- Download the
faketime-agent.jarfor your operating system from the Maven Central repository.
<!-- Windows 32bit -->
<dependency>
<groupId>io.github.faketime-java</groupId>
<artifactId>faketime-agent</artifactId>
<version>0.8.0</version>
<classifier>windows32</classifier>
</dependency>
<!-- Windows 64bit -->
<dependency>
<groupId>io.github.faketime-java</groupId>
<artifactId>faketime-agent</artifactId>
<version>0.8.0</version>
<classifier>windows64</classifier>
</dependency>
<!-- macOS 32bit -->
<dependency>
<groupId>io.github.faketime-java</groupId>
<artifactId>faketime-agent</artifactId>
<version>0.8.0</version>
<classifier>mac32</classifier>
</dependency>
<!-- macOS 64bit -->
<dependency>
<groupId>io.github.faketime-java</groupId>
<artifactId>faketime-agent</artifactId>
<version>0.8.0</version>
<classifier>mac64</classifier>
</dependency>
<!-- Linux 32bit -->
<dependency>
<groupId>io.github.faketime-java</groupId>
<artifactId>faketime-agent</artifactId>
<version>0.8.0</version>
<classifier>linux32</classifier>
</dependency>
<!-- Linux 64bit -->
<dependency>
<groupId>io.github.faketime-java</groupId>
<artifactId>faketime-agent</artifactId>
<version>0.8.0</version>
<classifier>linux64</classifier>
</dependency>
- Unpack the
jarto get the agent, which isfaketime.dllon Windows andlibfaketimeon other systems. - Attach the agent to your Java program with following JVM arguments.
-agentpath:path/to/unpacked/faketime/binary
-XX:+UnlockDiagnosticVMOptions
-XX:DisableIntrinsic=_currentTimeMillis
-XX:CompileCommand=quiet
-XX:CompileCommand=exclude,java/lang/System.currentTimeMillis
-XX:CompileCommand=exclude,jdk/internal/misc/VM.getNanoTimeAdjustment
- Use system properties to manipulate
System.currentTimeMillis().
System.out.println(System.currentTimeMillis()); // 1234567890
System.setProperty("faketime.offset.ms", "-7890");
System.out.println(System.currentTimeMillis()); // 1234560000
System.setProperty("faketime.absolute.ms", "12345");
System.out.println(System.currentTimeMillis()); // 12345
Java 8 API
<dependency>
<groupId>io.github.faketime-java</groupId>
<artifactId>faketime-api</artifactId>
<version>0.8.0</version>
<scope>test</scope>
</dependency>
In case you get tired of converting everything to milliseconds there is a Java Time based API.
FakeTime.stopAt(LocalDateTime.of(2000, 11, 10, 9, 8, 7));
FakeTime.stopAt(2000, 11, 10, ZoneOffset.UTC);
FakeTime.offsetRealByMinutes(100);
FakeTime.offsetRealBy(Duration.ofHours(20));
FakeTime.restoreReal();
And in case you get annoyed by writing FakeTime all the time there is a handy mixin.
public class MyTest implements FakeTimeMixin {
@Test
public void someTimeTest() {
stopTimeAt(LocalDateTime.of(2000, 11, 10, 9, 8, 7));
stopTimeAt(2000, 11, 10, ZoneOffset.UTC);
offsetRealTimeByMinutes(100);
offsetRealTimeBy(Duration.ofHours(20));
}
@After
public void restoreRealTimeAfterTest() {
restoreRealTime();
}
}
JUnit rule
<dependency>
<groupId>io.github.faketime-java</groupId>
<artifactId>faketime-junit</artifactId>
<version>0.8.0</version>
<scope>test</scope>
</dependency>
This rule calls FakeTime.restoreReal() after every test, so you don't have to.
Note: when using faketime-junit you don't need to add faketime-api as a test dependency
public class MyTest implements FakeTimeMixin {
@Rule
public FakeTimeRule fakeTimeRule = new FakeTimeRule();
@Test
public void someTimeTest() {
stopTimeAt(2000, 11, 10);
assertThat(LocalDate.now()).isEqualTo(LocalDate.of(2000, 11, 10));
// next test will start with real time
}
}
Maven plugin
For further convenience there is a Maven plugin that downloads and unpacks the correct agent for your operating system. It then sets a property that you can use in surefire or failsafe plugins to attach the agent.
Full example here
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
<configuration>
<argLine>${faketime.argLine}</argLine>
</configuration>
</plugin>
<plugin>
<groupId>io.github.faketime-java</groupId>
<artifactId>faketime-maven-plugin</artifactId>
<version>0.8.0</version>
<executions>
<execution>
<goals>
<goal>prepare</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
Maven + IntelliJ
IntelliJ has a cool feature that reads argLine from pom.xml and adds all arguments to the IDE test runner. The only thing you need to do is to replace ${faketime.argLine} with literal arguments, since IntelliJ is not aware of ${faketime.argLine}.
Note: before running tests from IntelliJ make sure faketime-maven-plugin has downloaded the agent, otherwise tests won't start
Full example here
<properties>
<faketime.binary>libfaketime</faketime.binary>
</properties>
<profiles>
<profile>
<id>faketimeBinary</id>
<activation>
<os>
<family>windows</family>
</os>
</activation>
<properties>
<faketime.binary>faketime.dll</faketime.binary>
</properties>
</profile>
</profiles>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-failsafe-plugin</artifactId>
<version>2.22.1</version>
<configuration>
<argLine>
-agentpath:${project.build.directory}/${faketime.binary}
-XX:+UnlockDiagnosticVMOptions
-XX:DisableIntrinsic=_currentTimeMillis
-XX:CompileCommand=quiet
-XX:CompileCommand=exclude,java/lang/System.currentTimeMillis
-XX:CompileCommand=exclude,jdk/internal/misc/VM.getNanoTimeAdjustment
</argLine>
</configuration>
</plugin>
<plugin>
<groupId>io.github.faketime-java</groupId>
<artifactId>faketime-maven-plugin</artifactId>
<version>0.8.0</version>
<executions>
<execution>
<goals>
<goal>prepare</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
Maven + Eclipse
Note: before running tests from Eclipse make sure faketime-maven-plugin has downloaded the agent, otherwise tests won't start
Preferences > Java > Installed JREs > Select > Edit > Default VM arguments
# if you're on Windows
-agentpath:target/faketime.dll
-XX:+UnlockDiagnosticVMOptions
-XX:DisableIntrinsic=_currentTimeMillis
-XX:CompileCommand=quiet
-XX:CompileCommand=exclude,java/lang/System.currentTimeMillis
-XX:CompileCommand=exclude,jdk/internal/misc/VM.getNanoTimeAdjustment
# if you're on macOS/Linux
-agentpath:target/libfaketime
-XX:+UnlockDiagnosticVMOptions
-XX:DisableIntrinsic=_currentTimeMillis
-XX:CompileCommand=quiet
-XX:CompileCommand=exclude,java/lang/System.currentTimeMillis
-XX:CompileCommand=exclude,jdk/internal/misc/VM.getNanoTimeAdjustment
Gradle
There are no instructions for Gradle yet, but if you'll figure this out, then don't be shy to make a pull request. Basically, you need to download and unpack the correct agent artifact and then add some JVM arguments to the test runner.
