One minute starting guide

This guide is for the AssertJ core module. Quick start guides for other modules are here:

Maven

AssertJ artifacts are in the Maven central repository.

<dependency>
  <groupId>org.assertj</groupId>
  <artifactId>assertj-core</artifactId>
  <!-- use 2.8.0 for Java 7 projects -->
  <version>3.8.0</version>
  <scope>test</scope>
</dependency>

Gradle

For Gradle users (using the Maven Central Repository)

testCompile 'org.assertj:assertj-core:3.8.0'

Or version 2.8.0 for Java 7 projects

testCompile 'org.assertj:assertj-core:2.8.0'

If you use another dependency tool, please check this page to find the relevant assertj dependency declaration for your tool.

One static import to rule them all ...

import static org.assertj.core.api.Assertions.*;

... or many if you prefer

import static org.assertj.core.api.Assertions.assertThat;  // main one
import static org.assertj.core.api.Assertions.atIndex; // for List assertions
import static org.assertj.core.api.Assertions.entry;  // for Map assertions
import static org.assertj.core.api.Assertions.tuple; // when extracting several properties at once
import static org.assertj.core.api.Assertions.fail; // use when writing exception tests
import static org.assertj.core.api.Assertions.failBecauseExceptionWasNotThrown; // idem
import static org.assertj.core.api.Assertions.filter; // for Iterable/Array assertions
import static org.assertj.core.api.Assertions.offset; // for floating number assertions
import static org.assertj.core.api.Assertions.anyOf; // use with Condition
import static org.assertj.core.api.Assertions.contentOf; // use with File assertions

On Android use this static import :

import static org.assertj.core.api.Java6Assertions.*;

You can even configure your IDE, so that when you type as and trigger code completion, it will suggest assertThat, see this tip.

Type assertThat followed by the object under test and a dot ... and any Java IDE code completion will show you all available assertions.

assertThat(objectUnderTest). // code completion -> assertions specific to objectUnderTest

Code completion example for String assertions :

Screenshot of IDE completion

See some of AssertJ noteworthy features to get the maximum out of it !

You can learn more by looking at the AssertJ core javadoc.

Another way to extend your knowledge is the assertj-examples tests project. It covers what is possible with AssertJ Assertions with running code. You can clone the repository and run its tests ! (You need to run `mvn install` first, as the project also shows how to generate custom assertions.)