Sharing knowledge

by Oleg Atamanenko

Using AssertJ

AssertJ is a library which provides fluent strongly-typed assertions to use in unit tests.

Example of assertions written with AssertJ:

import io.github.uthark.blog.assertj.Assertions.assertThat;

// ... within @Test
User result = userDao.findByLogin("username");
assertThat(result).
    isNotNull().
    isActive().
    hasLogin("username");

As you can see assertions look much more readable. The integration of assertj into Maven project is very easy:

  1. Update pom.xml in parent module
<properties>
    <assertj-core.version>1.6.0</assertj-core.version>
    <assertj-assertions-generator-maven-plugin.version>1.2.0</assertj-assertions-generator-maven-plugin.version>
</properties>

<dependencyManagement>
    <dependency>
        <groupId>org.assertj</groupId>
        <artifactId>assertj-core</artifactId>
        <version>${assertj-core.version}</version>
        <scope>test</scope>
    </dependency>
</dependencyManagement>

<pluginManagement>
    <plugin>
        <groupId>org.assertj</groupId>
        <artifactId>assertj-assertions-generator-maven-plugin</artifactId>
        <version>${assertj-assertions-generator-maven-plugin.version}</version>
        <executions>
            <execution>
                <id>generate-assertions</id>
                <phase>generate-test-sources</phase>
                <goals>
                    <goal>generate-assertions</goal>
                </goals>
            </execution>
        </executions>
    </plugin>

</pluginManagement>
  1. Update pom.xml in child module
<dependencies>
    <dependency>
        <groupId>org.assertj</groupId>
        <artifactId>assertj-core</artifactId>
    </dependency>
</dependencies>
<build>
    <plugins>
        <plugin>
            <groupId>org.assertj</groupId>
            <artifactId>assertj-assertions-generator-maven-plugin</artifactId>
            <configuration>
                <!-- you can define collection packages: -->
                <packages>
                    <param>io.github.uthark.blog.assertj</param>
                </packages>

                <!-- Or specify classes one by one. -->
                <classes>
                    <param>io.github.uthark.blog.assertj.User</param>
                </classes>
            </configuration>
        </plugin>
    </plugins>
</build>

After this changes it is possible to generate assertions for the classes you want test:

mvn assertj:generate-assertions

By default assertj will generate assertion classes in target/generated-test-sources/assertj-assertions/, it is possible to override this behaviour by passing configuration element targetDir to plugin.

Additonal documentation for Maven plugin can be found here

Happy hacking!