ESM HMR Spec

A test suite to explore the behaviour of esm-hmr flavours.

The far cry hope is that an objective and verifiable set of rules might help with aligning behind a standard API. For the greater good of ESM adapters implementers and, ultimately, the users of your tool.

Install

git clone git@github.com:rixo/esm-hmr-spec.git
cd esm-hmr-spec
yarn

Usage

yarn test --snowpack

yarn test --vite

Development

esm-hmr-spec is powered by test-hmr v0.2+, itself powered by poorly lightly documented zoar test runner, and zorax extensions (themselves built upon the great zora essentialist testing library).

Here are a few tips about the most useful commands you can use...

NOTE thc (test-hmr cli) is aliased as test in package.json, but all the following commands are really just running thc itself... You could just as well use yarn thc or node_modules/.bin/thc.

Watch mode

yarn test --watch

In watch mode, pressing Enter will rerun the tests.

Also, further options can be passed / changed interactively, without the need to restart the test runner. The available options are essentially the same as the argument accepted by the cli (see bellow for a curated selection).

The interactive console accepts options in long (e.g. --filter) or shortcut form (e.g. -f), with or without the leading -- / -.

Adding ? after the option name will display the current option value. Adding ! will reset the option to false / empty.

Entering just !! (or pressing Esc) will reset all options to their initial value (that is, the value that have been passed to the cli command).

So you can do something like this ($ is the term, > is zoar's interactive console):

$ zoar -w -f sanity
...
> f? # show the current filter
> f! # reset the filter
...
> ls # print matched files (switches to ls mode)
> f single # change the filter (and rerun ls)
> run #  run the tests (switches back to run mode)
...
> ib # debug the test in Node (short for --inspect-brk)
...
> ib! # stop debugging in Node
...
> e OPEN # open the browser while running test (allowing for in-browser debugging)
...
> e? # display current env variables that are passed to the test process
> e! # stop opening browser while running test
...
> !! # reset to initial options (`-f sanity`, in this example)

In default interactive (watch) console, entering any command will rerun the tests immediately. When you want to change several options at once, this might not be desirable. You can switch to deferred interactive mode by pressing :. In this mode, options are changed without rerunning the tests. Go back to fully interactive mode by pressing Enter or Ctrl+C.

Useful options

Help:

yarn test --help # -h

Run test process with --inspect-brk (allow debugging Snowpack code):

yarn test --inspect-brk # --ib

Open Playwright browser while running tests (with slowmo and also cancelling tests timeout -- allow debugging the JS running in the browser, by adding debugger in the fixtures' JS):

yarn test --open # -o

Display browser console output:

yarn test --console # -c

Filter tests by file name:

yarn test --filter sanity # -f sanity

Show the files matched by your filter:

yarn test --ls

Filter tests by test name:

yarn test --grep serve # -g serve

Print all the tests matched by the filters (instead of running them):

yarn test --print # -p

Modifier options can all be mixed and matched:

yarn test --filter sanity --grep serve --ls
yarn test --filter sanity --grep serve --print