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Time Warp
Virtual Time for the JVM

This library lets you create virtual-time clocks and install them as the JVM's clock to help with testing.

A virtual-time Clock will modify the operation of System.currentTimeMillis(), System.nanoTime(), Thread.sleep, Object.wait(long), LockSupport.parkNanos and any other operation relying on timeouts.

Use this library to slow-down/speed-up/manually control the JVM's clock to make your timing-sensitive tests less flaky.

Status

Early days. We've begun using TimeWarp's ScaledClock (and SystemClock) in Quasar tests. ManualClock hasn't been tested, so it probably doesn't work yet.

Usage

  1. Clone and build the repository with ./gradlew or use Maven artifact co.paralleluniverse:timewarp:0.1.0-SNAPSHOT from the Sonatype snapshot repository (https://oss.sonatype.org/content/repositories/snapshots)

  2. Add the JAR file to your bootstrap classpath with -Xbootclasspath/a:[timewarp jar] and as an agent with -javaagent:[timewarp jar]

  3. Install one of the provided clocks, SystemClock, ScaledClock, or ManualClock, using the VirtualClock class. Please consult the Javadocs for detailed information. Alternatively, you can pass an integer as a command-line argument to the agent (e.g. -javaagent:[timewarp jar]=3), which would install a global scaling clock, that would slow down the system clock by a factor equal to the parameter. So an argument of 3 would install a ScaledClock with a scaling factor of 0.33333.

License

MIT

Copyright (c) 2015-2016, Parallel Universe Software Co. All rights reserved.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.