chore: add to readme a guide how to update snaphots

router-tests/README.md

@@ -11,3 +11,18 @@ go test -race -v ./...
 ```
 
 It can take a while until the tests finish.
+
+## Updating fixtures
+
+Some of the tests uses the [goldie](https://github.com/sebdah/goldie) based snaphots
+
+In case you need to update all snaphots, you can run the following command:
+
+```bash
+go test -update ./...
+```
+
+Be aware that this will overwrite all snaphots with the current output of the tests.
+Use this command with caution.
+
+Alternatively you can update a single snaphot by temporarily replacing call to `g.Assert` with `g.Update` in the test and running the test.