retry tests

src/utils/retry.test.ts

+import { retry } from './retry'
+
+describe('retry', () => {
+  function makeFn<T>(fails: number, result: T): () => Promise<T> {
+    return async () => {
+      if (fails > 0) {
+        fails--
+        throw new Error('failure')
+      }
+      return result
+    }
+  }
+
+  it('works after one fail', async () => {
+    await expect(retry(makeFn(1, 'abc'), { n: 3, maxWait: 0, minWait: 0 })).resolves.toEqual('abc')
+  })
+
+  it('works after two fails', async () => {
+    await expect(retry(makeFn(2, 'abc'), { n: 3, maxWait: 0, minWait: 0 })).resolves.toEqual('abc')
+  })
+
+  it('throws if too many fails', async () => {
+    await expect(retry(makeFn(4, 'abc'), { n: 3, maxWait: 0, minWait: 0 })).rejects.toThrow('failure')
+  })
+
+  async function checkTime(fn: () => Promise<any>, min: number, max: number) {
+    const time = new Date().getTime()
+    await fn()
+    const diff = new Date().getTime() - time
+    expect(diff).toBeGreaterThanOrEqual(min)
+    expect(diff).toBeLessThanOrEqual(max)
+  }
+
+  it('waits random amount of time between min and max', async () => {
+    const promises = []
+    for (let i = 0; i < 10; i++) {
+      promises.push(
+        checkTime(
+          () => expect(retry(makeFn(4, 'abc'), { n: 3, maxWait: 100, minWait: 50 })).rejects.toThrow('failure'),
+          150,
+          305
+        )
+      )
+    }
+    await Promise.all(promises)
+  })
+})

src/utils/retry.ts

@@ -3,7 +3,7 @@ function wait(ms: number): Promise<void> {
 }
 
 function waitRandom(min: number, max: number): Promise<void> {
-  return wait(min + Math.round(Math.random() * (max - min)))
+  return wait(min + Math.round(Math.random() * Math.max(0, max - min)))
 }
 
 /**