Merge pull request ReactiveX#1816 from tklever/fix-switch-test

test(switch): update test case to use correct operator

spec/operators/switch-spec.ts

@@ -38,7 +38,7 @@ describe('Observable.prototype.switch', () => {
           unsubbed.push(x);
         };
       }))
-    .mergeAll()
+    .switch()
     .subscribe();
 
     expect(unsubbed).to.deep.equal(['a', 'b']);