Run tests with an X virtual framebuffer (1024x768)

The GitHub-hosted runner is a virtual machine hosted by GitHub.

Xvfb on that setup defaults to a virtual screen size of 640x480
(XVFBARGS='-screen 0 640x480x16') which in turn makes the Arduino user
interface tests fail with exceptions like this:

    [junit] org.fest.swing.exception.ActionFailedException: The component to click is out of the boundaries of the screen
    [junit] 	at org.fest.swing.exception.ActionFailedException.actionFailure(ActionFailedException.java:33)
    [junit] 	at org.fest.swing.core.RobotEventGenerator.pressMouse(RobotEventGenerator.java:74)

Setting the xvfb screen size to 1024x768 solves this error.

Author: tlk

.github/workflows/ant.yml

@@ -18,6 +18,10 @@ jobs:
       run: |
         sed -i 's#<input .*/>##' build.xml
         ant clean dist
+    - name: Install X virtual framebuffer
+      run: sudo apt-get install -y xvfb
     - name: Run tests
       working-directory: ./app
-      run: ant test
+      run: xvfb-run --auto-servernum --server-args "-screen 0 1024x768x24" ant test
+    - name: Cleanup xvfb
+      uses: bcomnes/cleanup-xvfb@v1