Attempt alternate workaround for CI race

Editor.Tests/Extensions/CommandServiceExtensions.cs

@@ -70,9 +70,30 @@ public static void CheckAndExecute<T> (
 						LogTrace ("Session open");
 						RegisterTraceHandlers (session);
 					}
+					// If we have a session, but it hasn't started yet, wait for it to start.
+					// We previously only called session.GetComputedItems to wait for the completion
+					// to be updated, but on slow machines, e.g. on CI, this could cause completion
+					// to be dismissed (TryDismissSafelyAsync) before it was even shown.
+					if (session is IAsyncCompletionSessionOperations sessionOperations) {
+						if (!sessionOperations.IsStarted) {
+							if (EnableDebugTrace) {
+								LogTrace ("Session is not started");
+							}
+							// wait up to 2.5 seconds in 25ms intervals
+							for (int i = 0; i < 100; i++) {
+								if (sessionOperations.IsStarted) {
+									if (EnableDebugTrace) {
+										LogTrace ("Session started after {i * 25}ms");
+									}
+									break;
+								}
+								Thread.Sleep (25);
+							}
+						}
+					}
+
 					//ensure the computation is completed before we continue typing
 					session.GetComputedItems (CancellationToken.None);
-					LogTrace ("Session open");
 				}
 			} else{
 				LogTrace ("Session not open");