Arcane workaround to fix a flaky test

For an inexplicable reason, the first time the selection
occurs, the value is incorrect. We often miss this error
in our tests if the expectation is reached before the
selection changed event fires.

It seems that the _second_ time the selection changed
event fires, the value is correct.

This change ensures we wait for the second selection change.
And we avoid running expectations until then.e

Author: aeisenberg

extensions/ql-vscode/src/vscode-tests/no-workspace/query-history.test.ts

@@ -402,14 +402,29 @@ describe('query-history', () => {
       });
     });
 
-    it('should get the selection from the treeView when both selections are empty', async () => {
+    it('should get the selection from the treeView when both selections are empty', async function() {
+      this.timeout(999999999);
       queryHistoryManager = await createMockQueryHistory(allHistory);
-      await queryHistoryManager.treeView.reveal(allHistory[1], { select: true });
-      const selection = (queryHistoryManager as any).determineSelection(undefined, undefined);
-      expect(selection).to.deep.eq({
-        finalSingleItem: allHistory[1],
-        finalMultiSelect: [allHistory[1]]
+      const p = new Promise<void>(done => {
+        queryHistoryManager!.treeView.onDidChangeSelection(s => {
+          if (s.selection[0] !== allHistory[1]) {
+            return;
+          }
+          const selection = (queryHistoryManager as any).determineSelection(undefined, undefined);
+          expect(selection).to.deep.eq({
+            finalSingleItem: allHistory[1],
+            finalMultiSelect: [allHistory[1]]
+          });
+          done();
+        });
       });
+
+      // I can't explain why, but the first time the onDidChangeSelection event fires, the selection is
+      // not correct (it is inexplicably allHistory[2]). So we fire the event a second time to get the
+      // correct selection.
+      await queryHistoryManager.treeView.reveal(allHistory[0], { select: true });
+      await queryHistoryManager.treeView.reveal(allHistory[1], { select: true });
+      await p;
     });
 
     it('should get the selection from the treeDataProvider when both selections and the treeView are empty', async () => {