UnhandledPromiseRejectionWarning: browser disconnected. This problem may appear when a browser hangs or is closed, or due to network issues.

[gyopiazza]

Are you requesting a feature or reporting a bug?

Bug

What is the current behavior?

TestCafe randomly stops execution while running tests with this error:

(node:8659) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: The HeadlessChrome 0.0.0 / Mac OS X 10.12.5 browser disconnected. This problem may appear when a browser hangs or is closed, or due to network issues.
(node:8659) [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.

Sometimes I also get this error:

(node:5426) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): TypeError: First argument must be a string or Buffer

What is the expected behavior?

The tests should run (and pass or fail).

How would you reproduce the current behavior (if this is a bug)?

Try running many tests at once with some concurrency. I tried running them in many different combinations of concurrency and amount of tests but the errors still randomly appear.

Specify your

• operating system: macOS 10.12.5
• testcafe version: 0.17.2
• node.js version: 8.4.0

As a sidenote, the error doesn't seem related with the moment problem as mentioned in other tickets, I also tried following the solution from #1769 but it didn't help. What else could I try? Thanks!

[AndreyBelym]

Hello @gyopiazza!

How do you start TestCafe? It seems like you're using TestCafe API, do you? Could you provide a code that runs TestCafe please?

This error means that a browser stopped responding in the testing process. There is a lot of reasons why it can happen, so sharing your tests and the test page would be really helpful, can you afford this?

BTW, if we can't figure the actual reason why browsers hangs, at least we can restart the browser (#1815), or if it's concurrency mode, just we can just keep using another instances that stayed alive. I think it will be not so hard to implement it \cc @AlexanderMoskovkin

[gyopiazza]

Hey @AndreyBelym!

Thanks for the fast response, and you guessed right, I'm using the TestCafe API. The tests are just simple click/type/waitFor actions which I don't think it's related to the problem because it happens randomly. Please let me know if an example of the tests I run could give you more hints and I'll share it too. This is how I instantiate TestCafe:

const tests = ['test1.js', 'test2.js' /*...*/];
createTestCafe('localhost', 9918, 9919)
        .then(tc => {
           const testcafe = tc;
           const runner = testcafe.createRunner();

           return runner
              .src(tests)
              .browsers('chrome:headless')
              .concurrency(10)
              .run({
                 skipJsErrors: true,
                 quarantineMode: true
               });
        })
        .then(failedCount => {
            console.log('Tests failed: ' + failedCount);
        })
        .catch(function(error) {
            throw(error);
        });

I expected the "quarantine" mode to take care of these situations but I guess it only kicks-in when the actual tests fail, and not for other errors. At first I thought it could be a "computer resources bottleneck" so I tried with a very low concurrency of 2 and even 1 (no concurrency) but the error still randomly appears. However, it didn't happen in the old version of TestCafe (>15.1.317053) but we could really benefit of the concurrency and other new features.

Your idea of restarting the browser or use another available instance sounds exactly what we need here. Basically when the browser is not responding TestCafe could kill the process and spawn a new one, without crashing the whole tests suite.

[AlexanderMoskovkin]

@AndreyBelym, @gyopiazza I agree with you, the #1815 proposal looks good. I think we can do this in the next releases.

[AlexanderMoskovkin]

closed in favor of #1815

[lock]

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