Add local config instructions to README.

README.md

@@ -7,6 +7,7 @@
   - [Background](#background)
   - [Install](#install)
   - [Usage](#usage)
+    - [Testing Locally](#testing-locally)
   - [Implementation](#implementation)
   - [Docker Integration (TODO)](#docker-integration-todo)
   - [Contribute](#contribute)
@@ -29,6 +30,45 @@ npm i
 npm test
 ```
 
+### Testing Locally
+
+If you want to test your implementations for endpoints running locally, you can
+create a configuration file `.localImplementationsConfig.cjs` in the root
+directory of the test suite.
+
+This file must be a CommonJS module that exports an array of implementations:
+
+```js
+// .localImplementationsConfig.cjs defining local implementations
+// you can specify a BASE_URL before running the tests such as:
+// BASE_URL=http://localhost:40443/zDdfsdfs npm test
+const baseURL = process.env.BASE_URL || 'https://localhost:40443/id'
+module.exports = [{
+  "name": "My Company",
+  "implementation": "My Implementation Name",
+  "issuers": [{
+    "id": "did:myMethod:implementation:issuer:id",
+    "endpoint": `${baseUrl}/credentials/issue`,
+    "tags": ["eddsa-rdfc-2022", "localhost"]
+  }],
+  "verifiers": [{
+    "id": "did:myMethod:implementation:verifier:id",
+    "endpoint": `${baseURL}/credentials/verify`,
+    "tags": ["eddsa-rdfc-2022", "localhost"]
+  }]
+}];
+```
+
+After adding the config file, both the localhost implementations and other
+non-localhost implementations will be included in the test run.
+
+To specifically test only the localhost implementation, modify the test suite to
+filter implementations based on a specific tag in your local configuration file.
+
+For instance, if your `.localImplementationsConfig.cjs` config file looks like
+above in the `di-eddsa-2022-test-suite`, you can adjust the tag used in each test
+file of the test suite to filter the implementations by `localhost` instead of `eddsa-rdfc-2022`.
+
 ## Implementation
 
 You will need an issuer and verifier that are compatible with [VC API](https://w3c-ccg.github.io/vc-api/)