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- By default, Jest imposes a
maximum timeout of 5 seconds

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for a test to complete.

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Which is reasonable for most tests

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in a unit-test environment.

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On the other hand, if you do
have a test that takes longer

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than 5 seconds, you have
configure Jest to wait longer

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so that it doesn't give up the ghost.

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So we're going to see how
to do that in this lesson,

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in this section.

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If you go into the
TestingCallbacks_Timeouts folder,

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this is what it looks
like, in the code listings.

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If you open up that
folder in the code editor,

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you'll see we have test code here.

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The code we're gonna actually test here,

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let's look at that function first.

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Here is a very slow operation.

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It waits 8 seconds, and
then after 8 seconds,

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it calls the callback function.

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So, if I try to test that
function, it's gonna blow up.

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Jest is gonna give up after 5 seconds.

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It can't bother to wait beyond that time.

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So, we're gonna see how to
configure Jest to wait longer.

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Okay, so, here's the
function we just looked at,

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verySlowOperation, it
has an 8-second time span

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before it completes.

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Okay, and here's my test,
as you can see here.

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By default, Jest will allow 5 seconds

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for this to complete.

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So, I've got the done prompter here,

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I seem to be doing things correctly.

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When this test executes, it
calls that slow operation.

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Ideally, after 8 seconds,
the testResult callback will

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be evoked with the return value.

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And at that point, I will
tell Jest, "I'm done here."

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The problem is that it's going
to take more than 5 seconds

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for this callback to occur,

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and Jest doesn't wait that long.

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So, let's see what happens
if we run this test

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as it stands.

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If I run the test using
the default timeout,

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that's the name of the
function I just showed you,

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this is the error that you'll get back.

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Basically, it shows that
Jest did not exit one second

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after the test run completed.

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It ran all test suites with
test matching that timer,

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but it failed, okay.

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It says that there was
an exceeded timeout,

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there was a 5 a second
timeout of 5000 milliseconds,

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due in which that test didn't complete.

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You could actually run that test,

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so you can see the 5 seconds elapse

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before the error message actually appears.

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Here's my command window.

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So I'll run Jest,

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and as an option,

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I'll pass in the name of my test:

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"test using default timeout."

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Okay, so, it'll call my test.

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It'll give my test up to 5 seconds,

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thinking "surely, that's
going to be long enough."

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And, well, it isn't long enough,

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and "stop calling me Shirley,"

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as they say in the airplane movie.

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There we go.

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So, it exceeded the timeout
of 5000 milliseconds

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for that test to complete.

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Okay, so, now the problem is

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if the function takes
longer than 5 seconds,

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then it takes longer than 5 seconds.

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We have to tell Jest to wait longer.

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So, the way you can do that,

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is you can actually pass
in a third parameter

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to the test function.

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The first parameter is
the name of the test,

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and the second parameter
is basically your lambda,

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you know, the function
that defines your test,

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and here's an extra third parameter,

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we haven't seen this before.

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This is the number of milliseconds

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that for this particular test

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that Jest will allow for it to complete.

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Okay, so, this test here
"test using specific timeout,"

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it'll allow 10 seconds
for that test to complete,

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and that should be enough.

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So, if I ran that test function now,

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"testing using specific timeout,"

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then it should complete successfully.

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I'm just gonna actually do that live,

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just to prove the point.

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Okay, so, "test using," this
test function was called

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"test using specific timeout."

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So, it'll allow up to 10 seconds.

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My function actually takes 8 seconds,

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at which point, it calls back,

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and then I tell Jest, "we're done now."

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So, in 8 seconds, I'm in
the process of transpiring,

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and then it finished.

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Okay, so, there we are on a
function-by-function basis,

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you can specify the timeout you want

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for an individual function to occur.

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Now, if you have lots of tests,

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and they all need to
have an extended timeout,

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then you can define kind
of like a global timeout,

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like this.

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In some kind of setup code,
you'd call "jest.setTimeout,"

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and this would then
apply for all functions,

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all test functions by default.

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This is the new default
for all my test functions.

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Okay, so, make that
function call somewhere

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in your test code.

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I put in the file called "setupTests.js,"

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there's nothing special
about that file name,

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you do have to tell Jest
about that file name,

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and we've seen before,

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in your Jest config
file- that is important,

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that file name- you say:

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"this is the code I want
to run to configure Jest."

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So, you give it the name
of your setupTests file-

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or multiple files if you want to-

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it'll then configure that test,
that timeout for all tests,

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and we're in business.

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When I have done that, in the demos,

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you might be wondering why

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that test timeout didn't actually kick in.

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I do have a setupTests,
but it's commented out.

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For the purposes of the demo,
that statement was commented.

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So I'll uncomment it.

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Okay, so, that now applies by default

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for all tests.

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Don't forget you have to
tell Jest about that file.

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So in your Jest config,

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you do have to point it to that file,

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like I've done.

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And now, all tests will
be subjected to set

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10-second timeout.

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So, in my tests, this first test,

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that didn't have timeout,

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will now default to ten.

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Okay.

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And that one has 10 specified anyway.

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And this test here
doesn't specify a timeout,

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it will also default to 10 seconds.

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All tests, now, will have
a default of 10 seconds.

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So, I can run all the tests,

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and they should all work.

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That's the theory, so I run
all the tests like this,

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and we should find that all
of those 3 tests work fine.

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The proof of the pudding
is in the eating, so,

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let's actually try that.

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So, "jest."

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So, it's going to run, it's
going to allow 10 seconds

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for each test by default,
so this is gonna take

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probably around 24 seconds,

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by the time it allows 8
seconds for the first test,

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8 seconds for the second one,

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8 seconds for the third one,

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and then after 24 seconds, it should say,

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"everything's worked fine."

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Okay, so, I think we
must getting quite close

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to the 24 seconds now,
the excitement is growing.

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24 seconds seems like an awful long time

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when you're waiting for the finish.

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Oh, there we go.

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Okay, so, you can either
set a global timeout,

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or you can set a timeout
on a test-by-test basis.

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You might find that
some tests need longer,

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and some tests need shorter.

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So, either pass in a third
parameter -t test function

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on a case-by-case basis,
or set a global timeout

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like we've seen in this last example.