EqualsVerifier

EqualsVerifier can be used in Java unit tests to verify whether the contract for the equals and hashCode methods in a class is met. The Maven coordinates are:

<dependency>
    <groupId>nl.jqno.equalsverifier</groupId>
    <artifactId>equalsverifier</artifactId>
    <version>3.10</version>
    <scope>test</scope>
</dependency>

Note that there's also a 'fat' jar with no transitive dependencies with artifactId equalsverifier-nodep.

Documentation

Please see the project's website.

Contribution

Pull requests are welcome! If you plan to open one, please also register an issue or send a message to the Google Group, so we can discuss it first. It would be a shame to put in a lot of work on something that isn't a good fit for the project. Also, I can help you by giving pointers on where to find certain things.

Development

Build

To build EqualsVerifier, you need Maven. Just call mvn from the command-line, without any parameters, and you're done. Alternatively, you can use any IDE with Maven support.

There are several Maven profiles that can be enabled or disabled:

profile	activation	purpose
`modules-jdk8`	JDK 8 up to but not including 11	Build only the modules that are compatible with Java 8 and up.
`modules-jdk11`	JDK 11 up to but not including 16	Build only the modules that are compatible with Java 11 and up.
`modules-jdk16`	JDK 16	Build only the modules that are compatible with Java 16 and up.
`modules-jdk17`	JDK 17 and up	Build all modules and build releaseable artifacts.
`static-analysis`	JDK 17 and up, and `disableStaticAnalysis` property must be off	Run static analysis checks. This only happens on a recent JDK. Can be disabled by running `mvn verify -DdisableStaticAnalysis`
`argline-preview`	`preview` property must be on	Enable Java preview features. Can be activated by running `mvn verify -Dpreview`
`argline-experimental`	`experimental` property must be on	Enables ByteBuddy experimental features; useful for testing EqualsVerifier on Early Access JDK builds. Can be activated by running `mvn verify -Dexperimental`
`pitest`	manual	Used by PITest integration on GitHub. Can be activated by running `mvn verify -Ppitest`

Formatting

EqualsVerifier uses Prettier-Java through Spotless to format Java files. You can call it using mvn (without any parameters), which will also run the tests and all the other static analysis. Or run mvn spotless:apply to only run the formatter.

Modules

This project is a multi-module project to make it easier to deal with shading and multi-release jar files. See this question on StackOverflow for the rationale behind it.

Here's a description of the modules:

module	purpose
docs	project's Jekyll website
equalsverifier-core	the actual EqualsVerifier code
equalsverifier-11	tests for Java 11 and up
equalsverifier-16	logic for records, and corresponding tests
equalsverifier-17	logic for sealed classes, and corresponding tests
equalsverifier-test-core	tests for the core code
equalsverifier-test-plumbing	helpers for tests that are used by multiple projects
equalsverifier-aggregator	generic release assembly description, and shared jacoco configuration
equalsverifier-release-main	release assembly for jar with dependencies
equalsverifier-release-nodep	release assembly for fat jar (with dependencies shaded in)

Signed JAR

The lib/ folder in the equalsverifier-test-core module contains a local Maven repository containing a signed JAR, used to test potential ClassLoader issues. Here's how to install a JAR into it:

mvn org.apache.maven.plugins:maven-install-plugin:2.3.1:install-file \
                        -Dfile=&lt;path-to-file> -DgroupId=&lt;myGroup> \
                        -DartifactId=&lt;myArtifactId> -Dversion=&lt;myVersion> \
                        -Dpackaging=&lt;myPackaging> -DcreateChecksum=true \
                        -DlocalRepositoryPath=equalsverifier-test-core/lib

The signed JAR itself can be found in this repo.

EqualsVerifier

General

Additional

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EqualsVerifier

Documentation

Contribution

Development

Build

Formatting

Modules

Signed JAR

Disclaimer