Guarantee idempotence of CountdownElement#start

18F · Mar 15, 2022 · 4258680 · 4258680
1 parent 8492b80
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diff --git a/app/javascript/packages/countdown-element/index.spec.ts b/app/javascript/packages/countdown-element/index.spec.ts
@@ -102,4 +102,17 @@ describe('CountdownElement', () => {
 
     expect(element.textContent).to.equal('0 minutes and 2 seconds');
   });
+
+  describe('#start', () => {
+    it('is idempotent', () => {
+      const element = createElement({ startImmediately: 'false' });
+
+      sinon.spy(element, 'setTimeRemaining');
+
+      element.start();
+      element.start();
+
+      expect(clock.countTimers()).to.equal(1);
+    });
+  });
 });
diff --git a/app/javascript/packages/countdown-element/index.ts b/app/javascript/packages/countdown-element/index.ts
@@ -42,6 +42,7 @@ export class CountdownElement extends HTMLElement {
   }
 
   start(): void {
+    this.stop();
     this.setTimeRemaining();
     this.#pollIntervalId = window.setInterval(() => this.setTimeRemaining(), this.updateInterval);
   }