Headless Swing Tests in Java

Headless Swing Tests in Java

Automated tests of GUIs is allways a problem. Keep in mind, that all tests need to run in a headless environment - your build server runs on a headless machine, right? For browser based applications there are tools. For Swing based GUIs there were strange suggestions building virtual machines that are controlled by the build process.

Here comes CacioCavallo into play. It simulates a graphics display even in a headless environment. Now tests using e.g. assertj-swing do work.

Using maven you need to include this to start

<dependency>
    <groupId>com.github.caciocavallosilano</groupId>
    <artifactId>cacio-tta</artifactId>
    <scope>test</scope>
    <version>1.11</version>  <!-- java 11 -->
    <version>1.17</version>  <!-- java 17 -->
    <version>1.18</version>  <!-- java 21 -->
</dependency>
<dependency>
    <groupId>org.assertj</groupId>
    <artifactId>assertj-swing</artifactId>
    <version>3.17.1</version>
    <scope>test</scope>
</dependency>

Be sure to configure your surefire plugin the right way:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>2.12</version>
  <configuration>
    <systemPropertyVariables>
      <java.awt.headless>false</java.awt.headless>
      <awt.toolkit>com.github.caciocavallosilano.cacio.ctc.CTCToolkit</awt.toolkit>
      <java.awt.graphicsenv>com.github.caciocavallosilano.cacio.ctc.CTCGraphicsEnvironment</java.awt.graphicsenv>
    </systemPropertyVariables>
    <argLine>
      --add-exports=java.desktop/java.awt=ALL-UNNAMED
      --add-exports=java.desktop/java.awt.peer=ALL-UNNAMED
      --add-exports=java.desktop/sun.awt.image=ALL-UNNAMED
      --add-exports=java.desktop/sun.java2d=ALL-UNNAMED
      --add-exports=java.desktop/java.awt.dnd.peer=ALL-UNNAMED
      --add-exports=java.desktop/sun.awt=ALL-UNNAMED
      --add-exports=java.desktop/sun.awt.event=ALL-UNNAMED
      --add-exports=java.desktop/sun.awt.datatransfer=ALL-UNNAMED
      --add-exports=java.base/sun.security.action=ALL-UNNAMED
      --add-opens=java.base/java.util=ALL-UNNAMED
      --add-opens=java.desktop/java.awt=ALL-UNNAMED
      --add-opens=java.desktop/sun.java2d=ALL-UNNAMED
      --add-opens=java.base/java.lang.reflect=ALL-UNNAMED
    </argLine>
  </configuration>
</plugin>

Using JUnit you need to annotate your class with

@RunWith(CacioAssertJRunner.class)