Adds a wait for FXEvents to try to fix tests on appveyor

Author: JLLeitschuh

ui/src/test/java/edu/wpi/grip/ui/MainWindowTest.java

@@ -9,6 +9,7 @@
 import org.junit.Test;
 import org.testfx.framework.junit.ApplicationTest;
 import org.testfx.matcher.base.NodeMatchers;
+import org.testfx.util.WaitForAsyncUtils;
 
 import static org.testfx.api.FxAssert.verifyThat;
 
@@ -40,6 +41,8 @@ public void testShouldCreateNewOperationInPipelineView() {
         // Given:
         clickOn("#add-operation");
 
+        WaitForAsyncUtils.waitForFxEvents();
+
         // Then:
         verifyThat(".pipeline", NodeMatchers.hasChild(".add-step"));
     }