Prevent possibility to launch same job multiple times simultaneously (#1

)

lib/engines/simple-interval/SimpleIntervalJob.ts

@@ -18,6 +18,11 @@ export class SimpleIntervalJob extends Job {
   start(): void {
     const time = toMsecs(this.schedule)
 
+    // Avoid starting duplicates and leaking previous timers
+    if (this.timer) {
+      this.stop()
+    }
+
     this.timer = setInterval(() => {
       this.task.execute()
     }, time)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "toad-scheduler",
-  "version": "1.0.1",
+  "version": "1.0.2",
   "license": "MIT",
   "description": "In-memory Node.js job scheduler",
   "maintainers": [

test/toadScheduler.spec.ts

@@ -69,6 +69,29 @@ describe('ToadScheduler', () => {
       scheduler.stop()
     })
 
+    it('correctly handles adding job twice', () => {
+      let counter = 0
+      const scheduler = new ToadScheduler()
+      const task = new Task('simple task', () => {
+        counter++
+      })
+      const job = new SimpleIntervalJob(
+        {
+          milliseconds: 10,
+        },
+        task
+      )
+
+      scheduler.addSimpleIntervalJob(job)
+      scheduler.addSimpleIntervalJob(job)
+
+      expect(counter).toBe(0)
+      jest.advanceTimersByTime(20)
+      expect(counter).toBe(2)
+
+      scheduler.stop()
+    })
+
     it('correctly stops jobs', () => {
       let counter = 0
       const scheduler = new ToadScheduler()