Add documentation for updating test snapshots

README.md

@@ -32,6 +32,16 @@ require_once(Netflex\SDK::bootstrap);
 composer run-script tests
 ```
 
+## Updating snapshots
+
+When an existing snapshot test has been updated, or its behaviour has been modified, the snapshot will have to be updated to prevent the tests from failing.
+
+To update the snapshots, run the following command.
+
+```bash
+composer run-script tests:update-snapshots
+```
+
 <hr>
 
 Copyright &copy; 2019 **[Apility AS](https://apility.no)**

composer.json

@@ -67,6 +67,7 @@
     "spatie/phpunit-snapshot-assertions": "^2.1"
   },
   "scripts": {
-    "tests": "vendor/bin/phpunit --testdox --colors=always"
+    "tests": "vendor/bin/phpunit --testdox --colors=always",
+    "tests:update-snapshots": "vendor/bin/phpunit --colors=always -d --update-snapshots"
   }
 }