Tests fail with UnhandledPromiseRejectionWarning

[nicokaiser]

There seems to be some kind of concurrency problem with the tests. When running npm test, an UnhandledPromiseRejectionWarning occurs and a test fails. When calling all the tests independently, all of them work.

  Limiter with ioredis
    .total
      ✓ should represent the total limit per reset period
    .remaining
      ✓ should represent the number of requests remaining in the reset period
    .reset
      ✓ should represent the next reset time in UTC epoch seconds
    when the limit is exceeded
      ✓ should retain .remaining at 0
      ✓ should return an increasing reset time after each call (2009ms)
    when the duration is exceeded
      ✓ should reset (3006ms)
    when multiple successive calls are made
      ✓ the next calls should not create again the limiter in Redis
      ✓ updating the count should keep all TTLs in sync
    when trying to decrease before setting value
      ✓ should create with ttl when trying to decrease
    when multiple concurrent clients modify the limit
(node:95644) UnhandledPromiseRejectionWarning: AssertionError: expected 2 to be 0
    at Assertion.fail (/Users/nkaiser/Code/github/async-ratelimiter/node_modules/should/cjs/should.js:275:17)
    at Assertion.value (/Users/nkaiser/Code/github/async-ratelimiter/node_modules/should/cjs/should.js:356:19)
    at /Users/nkaiser/Code/github/async-ratelimiter/test/index.js:181:33
    at process._tickCallback (internal/process/next_tick.js:68:7)
(node:95644) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:95644) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
      1) should prevent race condition and properly set the expected value

  9 passing (5s)
  1 failing

  1) Limiter with ioredis
       when multiple concurrent clients modify the limit
         should prevent race condition and properly set the expected value:

      AssertionError: expected 4 to be 5
      + expected - actual

      -4
      +5

      at Assertion.fail (node_modules/should/cjs/should.js:275:17)
      at Assertion.value (node_modules/should/cjs/should.js:356:19)
      at Context.<anonymous> (test/index.js:235:31)
      at process._tickCallback (internal/process/next_tick.js:68:7)

[Kikobeats]

Looks like tests are non-deterministic in some situations 🤔