fix(tests): fix flaky TestRunGameTask tests (#614)

* chore(tests): set spf4j-slf4j-test version to 8.8.5
* chore(spellcheck): `spdx` isn't exactly a word, but `SPDX` *is* expected in the copyright header
* fix(tests): make additions to `actualHistory` all happen on the Fx application thread.

Otherwise the entries from the test thread and the application thread are subject to race conditions, making for flaky tests.

build.gradle

@@ -118,7 +118,7 @@ dependencies {
     }
     testImplementation "org.mockito:mockito-junit-jupiter:3.3.+"
 
-    testImplementation('org.spf4j:spf4j-slf4j-test:8.8.+') {
+    testImplementation('org.spf4j:spf4j-slf4j-test:8.8.5') {
         because "testable logging"
     }
     testImplementation("org.slf4j:slf4j-api:1.7.+!!") {

src/test/java/org/terasology/launcher/game/TestRunGameTask.java

@@ -4,6 +4,7 @@
 package org.terasology.launcher.game;
 
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
+import javafx.application.Platform;
 import javafx.concurrent.WorkerStateEvent;
 import javafx.util.Pair;
 import org.junit.jupiter.api.AfterEach;
@@ -223,7 +224,8 @@ public void testSuccessEvent() throws Exception {
                 Happenings.TASK_COMPLETED.val()
         );
 
-        final Runnable handleLineSent = () -> actualHistory.add(Happenings.PROCESS_OUTPUT_LINE.val());
+        final Runnable handleLineSent = () -> Platform.runLater(
+                () -> actualHistory.add(Happenings.PROCESS_OUTPUT_LINE.val()));
 
         // This makes our "process," which streams out its lines and runs the callback after each.
         final Process lineAtATimeProcess = new MockProcesses.OneLineAtATimeProcess(
@@ -245,11 +247,10 @@ public void testSuccessEvent() throws Exception {
         // Act!
         executor.submit(gameTask);
 
-        WaitForAsyncUtils.waitForFxEvents();
-
         var actualReturnValue = gameTask.get();  // task.get blocks until it has run to completion
 
         // Assert!
+        WaitForAsyncUtils.waitForFxEvents();
         assertTrue(actualReturnValue);
 
         assertIterableEquals(expectedHistory, actualHistory, renderColumns(actualHistory, expectedHistory));
@@ -271,7 +272,8 @@ public void testFastExitDoesNotResultInSuccess() {
                 Happenings.TASK_FAILED.val()
         );
 
-        final Runnable handleLineSent = () -> actualHistory.add(Happenings.PROCESS_OUTPUT_LINE.val());
+        final Runnable handleLineSent = () -> Platform.runLater(
+                () -> actualHistory.add(Happenings.PROCESS_OUTPUT_LINE.val()));
 
         // This makes our "process," which streams out its lines and runs the callback after each.
         final Process lineAtATimeProcess = new MockProcesses.OneLineAtATimeProcess(
@@ -297,9 +299,9 @@ public void testFastExitDoesNotResultInSuccess() {
         // Act!
         executor.submit(gameTask);
 
-        WaitForAsyncUtils.waitForFxEvents();
-
         var thrown = assertThrows(ExecutionException.class, gameTask::get);
+
+        WaitForAsyncUtils.waitForFxEvents();
         assertThat(thrown.getCause(), instanceOf(RunGameTask.GameExitTooSoon.class));
 
         assertIterableEquals(expectedHistory, actualHistory, renderColumns(actualHistory, expectedHistory));