Globals
In your test files, Jest puts each of these methods and objects into the global environment. You don't have to require or import anything to use them. However, if you prefer explicit imports, you can do import {describe, expect, test} from '@jest/globals'
.
#
MethodsafterAll(fn, timeout)
afterEach(fn, timeout)
beforeAll(fn, timeout)
beforeEach(fn, timeout)
describe(name, fn)
describe.each(table)(name, fn, timeout)
describe.only(name, fn)
describe.only.each(table)(name, fn)
describe.skip(name, fn)
describe.skip.each(table)(name, fn)
test(name, fn, timeout)
test.concurrent(name, fn, timeout)
test.concurrent.each(table)(name, fn, timeout)
test.concurrent.only.each(table)(name, fn)
test.concurrent.skip.each(table)(name, fn)
test.each(table)(name, fn, timeout)
test.only(name, fn, timeout)
test.only.each(table)(name, fn)
test.skip(name, fn)
test.skip.each(table)(name, fn)
test.todo(name)
#
ReferenceafterAll(fn, timeout)
#
Runs a function after all the tests in this file have completed. If the function returns a promise or is a generator, Jest waits for that promise to resolve before continuing.
Optionally, you can provide a timeout
(in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.
This is often useful if you want to clean up some global setup state that is shared across tests.
For example:
Here the afterAll
ensures that cleanUpDatabase
is called after all tests run.
If afterAll
is inside a describe
block, it runs at the end of the describe block.
If you want to run some cleanup after every test instead of after all tests, use afterEach
instead.
afterEach(fn, timeout)
#
Runs a function after each one of the tests in this file completes. If the function returns a promise or is a generator, Jest waits for that promise to resolve before continuing.
Optionally, you can provide a timeout
(in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.
This is often useful if you want to clean up some temporary state that is created by each test.
For example:
Here the afterEach
ensures that cleanUpDatabase
is called after each test runs.
If afterEach
is inside a describe
block, it only runs after the tests that are inside this describe block.
If you want to run some cleanup just once, after all of the tests run, use afterAll
instead.
beforeAll(fn, timeout)
#
Runs a function before any of the tests in this file run. If the function returns a promise or is a generator, Jest waits for that promise to resolve before running tests.
Optionally, you can provide a timeout
(in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.
This is often useful if you want to set up some global state that will be used by many tests.
For example:
Here the beforeAll
ensures that the database is set up before tests run. If setup was synchronous, you could do this without beforeAll
. The key is that Jest will wait for a promise to resolve, so you can have asynchronous setup as well.
If beforeAll
is inside a describe
block, it runs at the beginning of the describe block.
If you want to run something before every test instead of before any test runs, use beforeEach
instead.
beforeEach(fn, timeout)
#
Runs a function before each of the tests in this file runs. If the function returns a promise or is a generator, Jest waits for that promise to resolve before running the test.
Optionally, you can provide a timeout
(in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.
This is often useful if you want to reset some global state that will be used by many tests.
For example:
Here the beforeEach
ensures that the database is reset for each test.
If beforeEach
is inside a describe
block, it runs for each test in the describe block.
If you only need to run some setup code once, before any tests run, use beforeAll
instead.
describe(name, fn)
#
describe(name, fn)
creates a block that groups together several related tests. For example, if you have a myBeverage
object that is supposed to be delicious but not sour, you could test it with:
This isn't required - you can write the test
blocks directly at the top level. But this can be handy if you prefer your tests to be organized into groups.
You can also nest describe
blocks if you have a hierarchy of tests:
describe.each(table)(name, fn, timeout)
#
Use describe.each
if you keep duplicating the same test suites with different data. describe.each
allows you to write the test suite once and pass data in.
describe.each
is available with two APIs:
describe.each(table)(name, fn, timeout)
#
1. table
:Array
of Arrays with the arguments that are passed into thefn
for each row.- Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e.
[1, 2, 3] -> [[1], [2], [3]]
- Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e.
name
:String
the title of the test suite.- Generate unique test titles by positionally injecting parameters with
printf
formatting:%p
- pretty-format.%s
- String.%d
- Number.%i
- Integer.%f
- Floating point value.%j
- JSON.%o
- Object.%#
- Index of the test case.%%
- single percent sign ('%'). This does not consume an argument.
- Or generate unique test titles by injecting properties of test case object with
$variable
- To inject nested object values use you can supply a keyPath i.e.
$variable.path.to.value
- You can use
$#
to inject the index of the test case - You cannot use
$variable
with theprintf
formatting except for%%
- To inject nested object values use you can supply a keyPath i.e.
- Generate unique test titles by positionally injecting parameters with
fn
:Function
the suite of tests to be ran, this is the function that will receive the parameters in each row as function arguments.- Optionally, you can provide a
timeout
(in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.
Example:
describe.each`table`(name, fn, timeout)
#
2. table
:Tagged Template Literal
- First row of variable name column headings separated with
|
- One or more subsequent rows of data supplied as template literal expressions using
${value}
syntax.
- First row of variable name column headings separated with
name
:String
the title of the test suite, use$variable
to inject test data into the suite title from the tagged template expressions, and$#
for the index of the row.- To inject nested object values use you can supply a keyPath i.e.
$variable.path.to.value
- To inject nested object values use you can supply a keyPath i.e.
fn
:Function
the suite of tests to be ran, this is the function that will receive the test data object.- Optionally, you can provide a
timeout
(in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.
Example:
describe.only(name, fn)
#
Also under the alias: fdescribe(name, fn)
You can use describe.only
if you want to run only one describe block:
describe.only.each(table)(name, fn)
#
Also under the aliases: fdescribe.each(table)(name, fn)
and fdescribe.each`table`(name, fn)
Use describe.only.each
if you want to only run specific tests suites of data driven tests.
describe.only.each
is available with two APIs:
describe.only.each(table)(name, fn)
#
describe.only.each`table`(name, fn)
#
describe.skip(name, fn)
#
Also under the alias: xdescribe(name, fn)
You can use describe.skip
if you do not want to run a particular describe block:
Using describe.skip
is often a cleaner alternative to temporarily commenting out a chunk of tests.
describe.skip.each(table)(name, fn)
#
Also under the aliases: xdescribe.each(table)(name, fn)
and xdescribe.each`table`(name, fn)
Use describe.skip.each
if you want to stop running a suite of data driven tests.
describe.skip.each
is available with two APIs:
describe.skip.each(table)(name, fn)
#
describe.skip.each`table`(name, fn)
#
test(name, fn, timeout)
#
Also under the alias: it(name, fn, timeout)
All you need in a test file is the test
method which runs a test. For example, let's say there's a function inchesOfRain()
that should be zero. Your whole test could be:
The first argument is the test name; the second argument is a function that contains the expectations to test. The third argument (optional) is timeout
(in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.
Note: If a promise is returned from
test
, Jest will wait for the promise to resolve before letting the test complete. Jest will also wait if you provide an argument to the test function, usually calleddone
. This could be handy when you want to test callbacks. See how to test async code here.
For example, let's say fetchBeverageList()
returns a promise that is supposed to resolve to a list that has lemon
in it. You can test this with:
Even though the call to test
will return right away, the test doesn't complete until the promise resolves as well.
test.concurrent(name, fn, timeout)
#
Also under the alias: it.concurrent(name, fn, timeout)
Use test.concurrent
if you want the test to run concurrently.
Note:
test.concurrent
is considered experimental - see here for details on missing features and other issues
The first argument is the test name; the second argument is an asynchronous function that contains the expectations to test. The third argument (optional) is timeout
(in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.
Note: Use
maxConcurrency
in configuration to prevents Jest from executing more than the specified amount of tests at the same time
test.concurrent.each(table)(name, fn, timeout)
#
Also under the alias: it.concurrent.each(table)(name, fn, timeout)
Use test.concurrent.each
if you keep duplicating the same test with different data. test.each
allows you to write the test once and pass data in, the tests are all run asynchronously.
test.concurrent.each
is available with two APIs:
test.concurrent.each(table)(name, fn, timeout)
#
1. table
:Array
of Arrays with the arguments that are passed into the testfn
for each row.- Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e.
[1, 2, 3] -> [[1], [2], [3]]
- Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e.
name
:String
the title of the test block.- Generate unique test titles by positionally injecting parameters with
printf
formatting:%p
- pretty-format.%s
- String.%d
- Number.%i
- Integer.%f
- Floating point value.%j
- JSON.%o
- Object.%#
- Index of the test case.%%
- single percent sign ('%'). This does not consume an argument.
- Generate unique test titles by positionally injecting parameters with
fn
:Function
the test to be ran, this is the function that will receive the parameters in each row as function arguments, this will have to be an asynchronous function.- Optionally, you can provide a
timeout
(in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.
Example:
test.concurrent.each`table`(name, fn, timeout)
#
2. table
:Tagged Template Literal
- First row of variable name column headings separated with
|
- One or more subsequent rows of data supplied as template literal expressions using
${value}
syntax.
- First row of variable name column headings separated with
name
:String
the title of the test, use$variable
to inject test data into the test title from the tagged template expressions.- To inject nested object values use you can supply a keyPath i.e.
$variable.path.to.value
- To inject nested object values use you can supply a keyPath i.e.
fn
:Function
the test to be ran, this is the function that will receive the test data object, this will have to be an asynchronous function.- Optionally, you can provide a
timeout
(in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.
Example:
test.concurrent.only.each(table)(name, fn)
#
Also under the alias: it.concurrent.only.each(table)(name, fn)
Use test.concurrent.only.each
if you want to only run specific tests with different test data concurrently.
test.concurrent.only.each
is available with two APIs:
test.concurrent.only.each(table)(name, fn)
#
test.only.each`table`(name, fn)
#
test.concurrent.skip.each(table)(name, fn)
#
Also under the alias: it.concurrent.skip.each(table)(name, fn)
Use test.concurrent.skip.each
if you want to stop running a collection of asynchronous data driven tests.
test.concurrent.skip.each
is available with two APIs:
test.concurrent.skip.each(table)(name, fn)
#
test.concurrent.skip.each`table`(name, fn)
#
test.each(table)(name, fn, timeout)
#
Also under the alias: it.each(table)(name, fn)
and it.each`table`(name, fn)
Use test.each
if you keep duplicating the same test with different data. test.each
allows you to write the test once and pass data in.
test.each
is available with two APIs:
test.each(table)(name, fn, timeout)
#
1. table
:Array
of Arrays with the arguments that are passed into the testfn
for each row.- Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e.
[1, 2, 3] -> [[1], [2], [3]]
- Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e.
name
:String
the title of the test block.- Generate unique test titles by positionally injecting parameters with
printf
formatting:%p
- pretty-format.%s
- String.%d
- Number.%i
- Integer.%f
- Floating point value.%j
- JSON.%o
- Object.%#
- Index of the test case.%%
- single percent sign ('%'). This does not consume an argument.
- Or generate unique test titles by injecting properties of test case object with
$variable
- To inject nested object values use you can supply a keyPath i.e.
$variable.path.to.value
- You can use
$#
to inject the index of the test case - You cannot use
$variable
with theprintf
formatting except for%%
- To inject nested object values use you can supply a keyPath i.e.
- Generate unique test titles by positionally injecting parameters with
fn
:Function
the test to be ran, this is the function that will receive the parameters in each row as function arguments.- Optionally, you can provide a
timeout
(in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.
Example:
test.each`table`(name, fn, timeout)
#
2. table
:Tagged Template Literal
- First row of variable name column headings separated with
|
- One or more subsequent rows of data supplied as template literal expressions using
${value}
syntax.
- First row of variable name column headings separated with
name
:String
the title of the test, use$variable
to inject test data into the test title from the tagged template expressions.- To inject nested object values use you can supply a keyPath i.e.
$variable.path.to.value
- To inject nested object values use you can supply a keyPath i.e.
fn
:Function
the test to be ran, this is the function that will receive the test data object.- Optionally, you can provide a
timeout
(in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.
Example:
test.only(name, fn, timeout)
#
Also under the aliases: it.only(name, fn, timeout)
, and fit(name, fn, timeout)
When you are debugging a large test file, you will often only want to run a subset of tests. You can use .only
to specify which tests are the only ones you want to run in that test file.
Optionally, you can provide a timeout
(in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.
For example, let's say you had these tests:
Only the "it is raining" test will run in that test file, since it is run with test.only
.
Usually you wouldn't check code using test.only
into source control - you would use it for debugging, and remove it once you have fixed the broken tests.
test.only.each(table)(name, fn)
#
Also under the aliases: it.only.each(table)(name, fn)
, fit.each(table)(name, fn)
, it.only.each`table`(name, fn)
and fit.each`table`(name, fn)
Use test.only.each
if you want to only run specific tests with different test data.
test.only.each
is available with two APIs:
test.only.each(table)(name, fn)
#
test.only.each`table`(name, fn)
#
test.skip(name, fn)
#
Also under the aliases: it.skip(name, fn)
, xit(name, fn)
, and xtest(name, fn)
When you are maintaining a large codebase, you may sometimes find a test that is temporarily broken for some reason. If you want to skip running this test, but you don't want to delete this code, you can use test.skip
to specify some tests to skip.
For example, let's say you had these tests:
Only the "it is raining" test will run, since the other test is run with test.skip
.
You could comment the test out, but it's often a bit nicer to use test.skip
because it will maintain indentation and syntax highlighting.
test.skip.each(table)(name, fn)
#
Also under the aliases: it.skip.each(table)(name, fn)
, xit.each(table)(name, fn)
, xtest.each(table)(name, fn)
, it.skip.each`table`(name, fn)
, xit.each`table`(name, fn)
and xtest.each`table`(name, fn)
Use test.skip.each
if you want to stop running a collection of data driven tests.
test.skip.each
is available with two APIs:
test.skip.each(table)(name, fn)
#
test.skip.each`table`(name, fn)
#
test.todo(name)
#
Also under the alias: it.todo(name)
Use test.todo
when you are planning on writing tests. These tests will be highlighted in the summary output at the end so you know how many tests you still need todo.
Note: If you supply a test callback function then the test.todo
will throw an error. If you have already implemented the test and it is broken and you do not want it to run, then use test.skip
instead.
#
APIname
:String
the title of the test plan.
Example: