append some cleaning stuff

app/build.gradle

@@ -103,9 +103,9 @@ task pack(type: io.github.fvarrui.javapackager.gradle.PackageTask, dependsOn: bu
     }
 }
 
-tasks.named('test') {
-    // Use JUnit Platform for unit tests.
-    useJUnitPlatform()
+clean.doFirst {
+  delete "${rootDir}/app/bin"
+  delete "${rootDir}/build"
 }
 
 javafx {
@@ -113,3 +113,7 @@ javafx {
     modules = ['javafx.controls', 'javafx.fxml', 'javafx.graphics']
 }
 
+tasks.named('test') {
+    // Use JUnit Platform for unit tests.
+    useJUnitPlatform()
+}