Update CONTRIBUTING.md (#49)

* Update CONTRIBUTING.md

* fmt

CONTRIBUTING.md

@@ -12,7 +12,15 @@ A suite of test-helpers exists to run `terraform apply` on modules with variable
 
 Reference existing `*.test.ts` files for implementation.
 
-```sh
+```shell
 # Run tests for a specific module!
 $ bun test -t '<module>'
 ```
+
+You can test a module locally by updating the source as follows
+
+```hcl
+source = "git::https://github.com/<USERNAME>/<REPO>.git//<MODULE-NAME>?ref=<BRANCH-NAME>"
+```
+
+> **Note:** This is the responsibility of the module author to implement tests for their module. and test the module locally before submitting a PR.