docs: add "Debug Tests"

CONTRIBUTING.md

@@ -80,4 +80,20 @@ A detailed explanation can be found in this [document](https://docs.google.com/d
 
 Don't edit wiki directly. Instead, edit files in the `/docs`.
 
-`/docs` is synced to wiki using git subtree merge when `next` release is marked as `latest` and available for all users.
+`/docs` is synced to wiki using git subtree merge when `next` release is marked as `latest` and available for all users.
+
+# Debug Tests
+
+Only IntelliJ Platform IDEs (IntelliJ IDEA, WebStorm) support debug. [Forked version of AVA](https://github.com/avajs/ava/pull/874) is used. Please see [AVA debug in the WebStorm](https://www.youtube.com/watch?v=C75UwuZXI98&feature=youtu.be).
+
+Use one of the shared run configurations as a template and:
+
+* Set `Node interpreter` to NodeJS 7. Yes — NodeJS 7 is required to debug. Download [nightly build](https://nodejs.org/download/nightly/).
+* Set `Node parameters` to `--inspect`.
+* Set `Application Parameters` to `--match="test name" relative-test-file-name` if you want to debug particular test. E.g.
+  ```
+  --match="extraResources - one-package" test/out/globTest.js
+  ```
+* Set `Environment Variables`:
+  * `NODE_PATH` to `.`.
+  * Optionally, `TEST_APP_TMP_DIR` to some directory (e.g. `/tmp/electron-builder-test`) to inspect output if test uses temporary directory (only if `--match` is used). Specified directory will be used instead of random temporary directory and *cleared* on each run.