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+# DevTools node tests
+
+In addition to mochitests and xpcshell tests, some panels in DevTools are using node test libraries to run unit tests. For instance, several panels are using [Jest](https://jestjs.io/) to run React component unit tests.
+
+## Find the node tests on Try
+
+The DevTools node tests are split in two different test suites on try:
+- `node(devtools)`: all the DevTools node tests, except the ones for the debugger
+- `node(debugger)`: only the Debugger node tests
+
+They are running on the `Linux 64 opt` platform. They are both tier 1 jobs, which means that any failure will lead to a backout.
+
+## Run Tests On Try
+
+To run the DevTools node tests on try, you can use `./mach try fuzzy` and look for the jobs named `source-test-node-debugger-tests` and `source-test-node-devtools-tests`.
+
+They are also run when using the "devtools" preset: `./mach try --preset devtools`.
+
+### Node tests try job definition
+
+The definition of those try jobs can be found at [taskcluster/ci/source-test/node.yml](https://searchfox.org/mozilla-central/source/taskcluster/ci/source-test/node.yml).
+
+The definition also contains the list of files that will trigger the node test jobs. Currently the debugger tests run when any file is modified under `devtools/client/debugger`, the devtools tests run when any file is modified under `devtools/client` or `devtools/shared`.
+
+## Run Tests Locally
+
+### Prerequisite: yarn
+
+You will need yarn to be installed in order to run both the debugger and the DevTools tests. See https://yarnpkg.com/docs/install/.
+
+### Debugger
+
+To run the debugger node tests:
+```
+> cd devtools/client/debugger/
+> yarn && node bin/try-runner.js
+```
+
+Note that the debugger is running other tasks than just unit tests: `flow`, `eslint`, `stylelint` etc...
+Using `yarn && yarn test` would only run the Jest tests, while `node bin/try-runner` will run the same tests and scripts as the ones used on try.
+
+### DevTools
+
+To run the other (non-debugger) DevTools tests, the easiest is to rely on the same script as the one used to run the tests on try:
+```
+> node devtools/client/bin/devtools-node-test-runner.js --suite={suitename}
+```
+
+At the moment of writing, the supported suites for this script are:
+- `aboutdebugging`
+- `accessibility`
+- `application`
+- `compatibility`
+- `framework`
+- `netmonitor`
+- `performance`
+- `shared_components`
+- `webconsole`
+
+(You can see the full list and the associated configuration in devtools/client/bin/devtools-node-test-runner.js)
+
+Alternatively, you can also locate the `package.json` corresponding to a given suite, and run `yarn && yarn test`.
+
+## Updating snapshots
+
+Some of the node tests are snapshot tests, which means they compare the output of a given component to a previous text snapshot. They might break if you are legitimately modifying a component and it means the snapshots need to be updated.
+
+A snapshot failure will show up as follows:
+```
+› 1 snapshot failed from 1 test suite
+```
+
+It should also mention the command you can run to update the snapshots:
+```
+Inspect your code changes or run `yarn run test-ci -u` to update them.
+```
+
+For example, if you need to update snapshots in a specific panel, first locate the package.json corresponding to the node test folder of the panel. In theory it should be under `devtools/client/{panelname}/test/node/` but it might be slightly different depending on each panel. Then run `yarn run test-ci -u` in this folder and add the snapshot changes to your commit.
+
+## TypeScript
+
+The "performance" suite performs TypeScript checks. The TypeScript usage in the performance panel is documented at [devtools/client/performance-new/typescript.md](https://searchfox.org/mozilla-central/source/devtools/client/performance-new/typescript.md) ([see rendered version on GitHub](https://github.com/mozilla/gecko-dev/blob/master/devtools/client/performance-new/typescript.md)).