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AssertJ provides a rich and intuitive set of strongly-typed assertions to use for unit testing (either with JUnit or TestNG).
- AssertJ's goals
- Latest News
- Quick start
- Features highlight
- [Assertions for your own custom types](#custom types-assertions)
- Replacing JUnit assertions by AssertJ Assertions
- Migrating from FEST Assertions
- Contributing
Documentation of all AssertJ projects is maintained on assertj.org, AssertJ Core documentation is here.
You can ask questions and make suggestions on AssertJ google group.
AssertJ's ambition is to provide a rich and intuitive set of strongly-typed assertions to use 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 the Map-specific assertions, which make it easy to check on the contents of the map.
AssertJ is composed of several modules:
- A core module (this one) to provide assertions for JDK types (String, Collections, 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, Relastionship ...) - see AssertJ Neo4J documentation and javadoc.
Assertion missing? Please create an issue!
AssertJ's assertions are super easy to write: just type assertThat followed by the actual value in parentheses and then a dot,
and any Java IDE will show you all the assertions available for the type of the object to verify. No more confusion about the
order of the "expected" and "actual" values. Our assertions are very readable as well: they read very close to plain
English, making it easier for non-technical people to read test code.
A lot of effort have been done to provide intuitive error messages showing as clearly as possible what the problem is.
Note that AssertJ 2.x requires at least Java 7 and AssertJ 3.x requires at least Java 8.
AssertJ core javadoc is published here.
To read details on the latest releases, please go to AssertJ Core latest news.
It is easy to start using AssertJ, follow the One minute starting guide.
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:
To help you replace JUnit assertions by AssertJ ones, you can use a script or do regexp search and replace manually as indicated here.
Check our migration guide, it covers migrating from Fest 1.4 and migrating from Fest 2.x.
You are encouraged to contribute any missing, useful assertions. To do so, please read the contributors section.