document standalone testrig

CONTRIBUTING.md

@@ -56,6 +56,41 @@ docker run -d --user postgres --network host sosedoff/pgweb
 
 This will launch a pgweb at `http://localhost:8081`.
 
+### Standalone Testrig
+
+You can also launch a testrig as a standalone server running at localhost, which you can connect to using something like [Pinafore](https://github.com/nolanlawson/pinafore).
+
+To do this, first build the gotosocial binary with `go build ./cmd/gotosocial`.
+
+Then launch a clean Postgres container on localhost:
+
+```bash
+docker run -d --user postgres --network host -e POSTGRES_PASSWORD=postgres postgres
+```
+
+Then, launch the testrig by invoking the binary as follows:
+
+```bash
+./gotosocial --host localhost:8080 testrig start
+```
+
+To run Pinafore locally in dev mode, first clone the Pinafore repository, and run the following command in the cloned directory:
+
+```bash
+yarn run dev
+```
+
+The Pinafore instance will start running on `localhost:4002`.
+
+To connect to the testrig, navigate to `https://localhost:4002` and enter your instance name as `localhost:8080`.
+
+At the login screen, enter the email address `zork@example.org` and password `password`.
+
+Note the following constraints:
+
+- The testrig data will be destroyed when the testrig is destroyed. It does this by dropping all tables in Postgres on shutdown. As such, you should **NEVER RUN THE TESTRIG AGAINST A DATABASE WITH REAL DATA IN IT** because it will be destroyed. Be especially careful if you're forwarding database ports from a remote instance to your local machine, because you can easily and irreversibly nuke that data if you run the testrig against it.
+- The testrig does not make any actual external http calls, so federation will (obviously) not work from a testrig.
+
 ## Running tests
 
 Because the tests use a real Postgres under the hood, you can't run them in parallel, so you need to run tests with the following command: