test(TestScheduler): add test for subscription marbles parser (#5867)

spec/schedulers/TestScheduler-spec.ts

@@ -125,12 +125,20 @@ describe('TestScheduler', () => {
       expect(result.unsubscribedFrame).to.equal(70);
     });
 
-    it('should suppport time progression syntax when runMode=true', () => {
+    it('should support time progression syntax when runMode=true', () => {
       const runMode = true;
       const result = TestScheduler.parseMarblesAsSubscriptions('10.2ms ^ 1.2s - 1m !', runMode);
       expect(result.subscribedFrame).to.equal(10.2);
       expect(result.unsubscribedFrame).to.equal(10.2 + 10 + (1.2 * 1000) + 10 + (1000 * 60));
     });
+
+    it('should throw if found more than one subscription point', () => {
+      expect(() => TestScheduler.parseMarblesAsSubscriptions('---^-^-!-')).to.throw();
+    });
+
+    it('should throw if found more than one unsubscription point', () => {
+      expect(() => TestScheduler.parseMarblesAsSubscriptions('---^---!-!')).to.throw();
+    });
   });
 
   describe('createTime()', () => {

src/internal/testing/TestScheduler.ts

@@ -243,7 +243,7 @@ export class TestScheduler extends VirtualTimeScheduler {
           break;
         case '!':
           if (unsubscriptionFrame !== Infinity) {
-            throw new Error('found a second subscription point \'^\' in a ' +
+            throw new Error('found a second unsubscription point \'!\' in a ' +
               'subscription marble diagram. There can only be one.');
           }
           unsubscriptionFrame = groupStart > -1 ? groupStart : frame;