docs: add guidance around Go tests (#9380)

* docs: add guidance around go tests

* docs: tweak instruction

* add instruction to run tests with make

* suggest deleteing artifacts directory

* settle on foundry update route

CONTRIBUTING.md

@@ -164,7 +164,7 @@ docker compose logs --follow <service name>
 
 Before running tests: **follow the above instructions to get everything built.**
 
-#### Running unit tests
+#### Running unit tests (typescript)
 
 Run unit tests for all packages in parallel via:
 
@@ -179,6 +179,16 @@ cd packages/package-to-test
 pnpm test
 ```
 
+#### Running unit tests (Go)
+
+Change directory to the package you want to run tests for. Then:
+```shell
+go test ./...
+```
+
+#### Running e2e tests (Go)
+See [this document](./op-e2e/README.md)
+
 #### Running contract static analysis
 
 We perform static analysis with [`slither`](https://github.com/crytic/slither).

op-e2e/README.md

@@ -19,3 +19,16 @@ runtime, but others cannot be changed or else it will result in
 broken tests. Any changes to `devnetL1.json` should result in
 rebuilding the `.devnet` artifacts before the new values will
 be present in the `op-e2e` tests.
+
+## Running tests
+Consult the [Makefile](./Makefile) in this directory. Run, e.g.:
+
+```bash
+make test-http
+```
+
+### Troubleshooting
+If you encounter errors:
+* ensure you have the latest version of foundry installed: `pnpm update:foundry`
+* try deleting the `packages/contracts-bedrock/forge-artifacts` directory
+* if the above step doesn't fix the error, try `pnpm clean`