AssertJ - Fluent assertions for java

master: 2.x:

AssertJ provides a rich and intuitive set of strongly-typed assertions to use for unit testing (either with JUnit or TestNG).

• AssertJ's goals
• Quick start
• Latest News
• Features highlight
• Assertions for custom types
• Replacing JUnit assertions with AssertJ Assertions
• Migrating from FEST Assertions
• Contributing

The AssertJ web site contains all projects documentation and can be found here. It notably includes the AssertJ Core documentation.

You can ask questions and make suggestions on AssertJ google group.

AssertJ's goals

AssertJ's ambition is to provide a rich and intuitive set of strongly-typed assertions for unit testing.

The idea is that, when writing unit tests, we should have at our disposal assertions specific to the type of the objects we are checking. If you're checking the value of a String, you use String-specific assertions. Checking the value of a Map? Use Map-specific assertions, which makes it easy to check the contents of the map.

AssertJ is composed of several modules:

• A core module (this one) to provide assertions for JDK types (String, Iterable, Stream, Path, File, Map...) - see AssertJ Core documentation and javadoc.
• A Guava module to provide assertions for Guava types (Multimap, Optional...) - see AssertJ Guava documentation and javadoc.
• A Joda Time module to provide assertions for Joda Time types (DateTime, LocalDateTime) - see AssertJ Joda Time documentation and javadoc.
• A Neo4J module to provide assertions for Neo4J types (Path, Node, Relationship...) - see AssertJ Neo4J documentation and javadoc.
• A DB module to provide assertions for relational database types (Table, Row, Column...) - see AssertJ DB documentation and javadoc.
• A Swing module provides a simple and intuitive API for functional testing of Swing user interfaces - see AssertJ Swing documentation and javadoc.

Assertion missing? Please create an issue!

AssertJ's assertions are super easy to use: just type assertThat followed by the actual value in parentheses and a dot, then any Java IDE will show you all assertions available for the type of the object. No more confusion about the order of "expected" and "actual" value.

AssertJ's assertions read very close to plain English.

A lot of effort has been spent to provide intuitive failure messages showing clearly why the assertion failed.

Note that AssertJ 3.x requires at least Java 8 and AssertJ 2.x requires at least Java 7.

Quickstart

It is easy to start using AssertJ, just follow the one minute starting guide.

Latest News

To read details on the latest releases, please go to AssertJ Core latest news.

Assertions for custom types

Having assertions for common types like List is great, but you might want some that are specific to your own types. This is possible with AssertJ because it is easily extensible so it's simple to write assertions for your custom types.

Moreover, to ease your work, we provide assertions generator that can take a set of custom types and create specific assertions. The tools provided are:

• A CLI assertions generator
• A Maven plugin assertions generator

Replacing JUnit assertions with AssertJ Assertions

To help you replace JUnit assertions with AssertJ ones, you can use a script or do regexp search and replace manually as described here.

Migrating from FEST Assertions

Check our migration guide, it covers migrating from Fest 1.4 and migrating from Fest 2.x.

Want to contribute?

You are encouraged to contribute any missing, useful assertions. To do so, please read the contributing section.