There are a few moments in the life of a test where you might want to attach some setup or teardown logic. Node-tap implements these using the following interfaces.
--before=before-tests.js
, --after=after-tests.js
To run a script before any tests are executed, specify it as a --before
config value. To run a script after all tests are done executing, specify
it as an --after
config value.
These can be set either on the CLI, in a .taprc
file, or package.json
file. (See Configuring Tap.)
--before
and --after
file's output will be sent to the parent's
terminal, and outside of any reporters. It's generally not a great idea
to have them output TAP, since that can cause the test
run to generate invalid output.
If the script exits in error (either via a status code or being killed by a
signal), then the test run will be aborted and exit in error. An --after
script will run even if the test run bails out.
A defined --before
or --after
script will be omitted if it would have
been included as a test file. So, it's fine to do something like tap
--before=test/setup.js --after=test/teardown.js test/*.js
.
There is no provided way to communicate context from a --before
or
--after
program, since they run in separate processes from the test
scripts, but since they are guaranteed to be run before or after any
parallel testing, it is safe to have them write data to files that can be
read by test scripts.
The other functions referenced below are for use within a test program.
t.beforeEach(fn(childTest))
Before any child test (or any children of any child tests, etc.) the supplied function is called with the test object that it's prefixing.
If the function returns a Promise, then that is used as the indication of
doneness. Thus, async
functions automatically end when all of their awaited
Promises are complete.
If the function does not return a Promise, then it is assumed to be completed synchronously.
Prior to v15, tap would call t.beforeEach()
functions with a done
callback to indicate completion. As of v15, Promises are the only way to
use these functions asynchronously.
t.afterEach(fn(childTest))
This is called after each child test (or any children of any child tests, on
down the tree). Like beforeEach
, it's called with the child test object,
and can return a Promise to perform asynchronous operations.
Prior to v15, tap would call t.afterEach()
functions with a done
callback to indicate completion. As of v15, Promises are the only way to
use these functions asynchronously.
t.before(fn())
t.before()
is a way to perform some actions before any subsequent tests
are run. If the function returns a Promise, then that Promise will be
awaited for completion before any subsequent t.test()
child tests are
executed.
The t.before()
method will never be filtered out by setting --only
or
--grep
configurations, so it is useful in cases where you might have a
lot of tests in a given file, but all of them depend on some initial
setup to be performed.
t.teardown(fn())
When the test is completely finished, the teardown functions are called. They
may return a Promise
to perform asynchronous actions.
t.on('end')
The end
event fires when the test is completely finished, and all of its
teardown functions have completed.
This is just a normal EventEmitter
event, so it doesn't support any sort of
async actions.
t.context
You can use the t.context
object to track details specific to a test. For
example, a beforeEach
function might create a database connection, and then
an afterEach
function might shut it down cleanly.
const myDataBase = require('my-special-db-thingie')
t.beforeEach(async t => {
t.context.connection = await myDataBase.connect()
})
t.afterEach(t => {
t.context.connection.disconnect()
})
t.test('read and write', t => {
const conn = t.context.connection
conn.write('foo', 'bar')
t.equal(conn.read('foo'), 'bar')
t.end()
})