Merge pull request atom#11541 from BrainCrumbz/doc-win-apm-path

📝 [ci skip] add notes on 'apm' path in Windows

docs/build-instructions/windows.md

@@ -36,6 +36,19 @@ To also install the newly built application, use `script\build --create-windows-
 * `--create-windows-installer`: creates an `.msi`, an `.exe` and a `.nupkg` installer in the `out/` directory.
 * `--install`: installs the application in `%LOCALAPPDATA%\Atom\app-dev\`.
 
+### Running tests
+
+In order to run tests from command line you need `apm`, available after you install Atom or after you build from source. If you installed it, run the following commands (assuming `C:\atom` is the root of your Atom repository):
+
+```bash
+cd C:\atom
+apm test
+```
+
+When building Atom from source, the `apm` command is not added to the system path by default. In this case, you can either add it yourself or explicitly list the complete path in previous commands. Anyway, its default location on a Win 64-bit installation is `"C:\Program Files (x86)\Atom\resources\cli\"`.
+
+**NOTE**: Please keep in mind that there are still some Windows tests that don't pass.
+
 ## Troubleshooting
 
 ### Common Errors