Fray is a concurrency testing tool for Java that can help you find and debug tricky race conditions that manifest as assertion violations, run-time exceptions, or deadlocks. It performs controlled concurrency testing using state-of-the-art techniques such as probabilistic concurrency testing or partial order sampling. Fray also provides deterministic replay capabilities for debugging specific thread interleavings. Fray is designed to be easy to use and can be integrated into existing testing frameworks.

If you are using JUnit 5, you can use the @ConcurrencyTest annotation to mark a test as a concurrency test. You also need to add the @ExtendWith(FrayTestExtension.class) annotation to the test class.

import org.pastalab.fray.junit.junit5.FrayTestExtension;
import org.pastalab.fray.junit.junit5.annotations.ConcurrencyTest;

@ExtendWith(FrayTestExtension.class)
public class SimpleTest {
    @ConcurrencyTest
    public void concurrencyTest() {
        ... // some multithreaded code
        assert(...);
    }
}

Fray can be used with other testing frameworks as well. You may use the FrayInTestLauncher

import org.pastalab.fray.junit.plain.FrayInTestLauncher;

public void test() {
    FrayInTestLauncher.INSTANCE.launchFrayTest(() -> {
        ... // some multithreaded code
        assert(...);
    });
}

To use Fray with Gradle, add the following plugin to your build.gradle file:

plugins {
    id("org.pastalab.fray.gradle") version "0.5.1"
}

• First please add Fray plugin to your project

<plugin>
    <groupId>org.pastalab.fray.maven</groupId>
    <artifactId>fray-plugins-maven</artifactId>
    <version>0.5.1</version>
    <executions>
        <execution>
            <id>prepare-fray</id>
            <goals>
                <goal>prepare-fray</goal>
            </goals>
        </execution>
    </executions>
</plugin>

• Next, please add the fray-junit dependency

<dependency>
    <groupId>org.pastalab.fray</groupId>
    <artifactId>fray-junit</artifactId>
    <version>0.5.1</version>
    <scope>test</scope>
</dependency>

Contributions to Fray are both welcomed and appreciated! Please see our contributing guide for more information on how to contribute to Fray.

This material is based upon work supported by the National Science Foundation under Grant No. 2120955. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

The Fray project was also supported by an Amazon Research Award.