Added test documentation to README

no issue

ghost/admin/.gitignore

@@ -38,6 +38,7 @@ Session.vim
 
 # compiled output
 /dist
+/dist-test
 /tmp
 
 # dependencies

ghost/admin/README.md

@@ -8,6 +8,57 @@ This is the home of Ember.js based admin app that ships with [Ghost](https://git
 
 **Do you want to modify or contribute to Ghost-Admin?** Please read how to [install from source](https://ghost.org/docs/install/source/) and swing by our [forum](https://forum.ghost.org) if you need any help 😄
 
+## Running tests
+
+Build and run tests once:
+
+```bash
+TZ=UTC yarn test
+```
+_Note the `TZ=UTC` environment variable which is currently required to get tests working if your system timezone doesn't match UTC._
+
+If you are serving the admin app (e.g., when running `yarn serve`, or when running `yarn dev` in the main Ghost project),  you can also run the tests in your browser by going to http://localhost:4200/tests. 
+
+This has the additional benefit that you can use `await this.pauseTest()` in your tests to temporarily pause tests. This allows you to inspect the DOM in your browser to debug tests. You can resume tests by running `resumeTest()` in your browser console.
+
+[More information](https://guides.emberjs.com/v3.28.0/testing/testing-application/#toc_debugging-your-tests)
+
+
+### Writing tests
+
+When writing tests and not using the `http://localhost:4200/tests` browser tests, it can be easier to have a separate watching build that builds the project for the test environment (this drastically reduces the time you have to wait when running tests):
+
+```bash
+yarn build --environment=test -w -o="dist-test"
+```
+
+After that, you can easily run tests locally:
+
+Run all tests:
+
+```bash
+TZ=UTC yarn test 1 --path="dist-test"
+```
+
+To have a cleaner output:
+
+```bash
+TZ=UTC yarn test 1 --reporter dot  --path="dist-test"
+```
+
+This shows a dot (`.`) for every successful test, and `F` for every failed test. At the end, it will only show the output of the failed tests.
+
+To run a specific test file:
+```bash
+TZ=UTC yarn test 1 --reporter dot  --path="dist-test" -mp=tests/acceptance/settings/newsletters-test.js
+```
+_Hint: you can easily copy the path of a test in VSCode by right clicking on the test file and choosing `Copy Relative Path`._
+
+To have a full list of the available options, run
+```bash
+ember exam --help
+```
+
 ## Have a bug or issue?
 
 Bugs and issues (even if they only affect the admin app) should be opened on the core [Ghost](https://github.com/tryghost/ghost/issues) repository.