Faketime

This native Java Agent allows you to change the time in a Java program, without affecting the system clock. It allows control over the System.currentTimeMillis() method, which is used by most other time-related functionality provided by the JVM.

How to use it

The easy way - For the Mac

Download libfaketime.jnilib into some directory, say, /path/to/libfaketime.jnilib.

Run your Java program (say, org.test.Main) with the agent-specific extra arguments (see issue #3), like this:

  java -agentpath:/path/to/libfaketime.jnilib \
    -XX:+UnlockDiagnosticVMOptions \
    -XX:DisableIntrinsic=_currentTimeMillis \
    -XX:CompileCommand=exclude,java/lang/System.currentTimeMillis \
    org.test.Main

In your Java code, you can set the property faketime.offset.seconds to the number of seconds you want the time altered by. For example, to add a day, you can do something like this:
```
  System.setProperty("faketime.offset.seconds", "86400");
```
You can also set property faketime.fixed.seconds to fix the time at a certain moment. For example, to set the date to 1 of January 1970, you can do something like this:
```
  System.setProperty("faketime.fixed.seconds", "0");
```
That's it! Take a look at FakeTimeTest.java if you need to see some Java code which uses it.

The "hard" way - For the Mac

Clone this repo

Run this:

  gcc -shared -I $JAVA_HOME/include -I $JAVA_HOME/include/darwin -Wall src/FakeTimeAgent.c -o libfaketime.jnilib

This will create libfaketime.jnilib in the current directory. Run your Java program (say, org.test.Main) with the agent-specific extra arguments, like this:

  java -agentpath:/path/to/libfaketime.jnilib \
    -XX:+UnlockDiagnosticVMOptions \
    -XX:DisableIntrinsic=_currentTimeMillis \
    -XX:CompileCommand=exclude,java/lang/System.currentTimeMillis \
    org.test.Main

or, if the current directory has libfaketime.jnilib, you can use:

  java -agentlib:faketime \
    -XX:+UnlockDiagnosticVMOptions \
    -XX:DisableIntrinsic=_currentTimeMillis \
    -XX:CompileCommand=exclude,java/lang/System.currentTimeMillis org.test.Main

In your Java code, you can set the property faketime.offset.seconds to the number of seconds you want the time altered by. For example, to add a day, you can do something like this:
```
  System.setProperty("faketime.offset.seconds", "86400");
```
You can also set property faketime.fixed.seconds to fix the time at a certain moment. For example, to set the date to 1 of January 1970, you can do something like this:
```
  System.setProperty("faketime.fixed.seconds", "0");
```
That's it! Take a look at FakeTimeTest.java if you need to see some Java code which uses it.

mihhail-lapushkin/faketime

Faketime

How to use it

The easy way - For the Mac

The "hard" way - For the Mac