Add snowplow to e2e docs (#47765)

* add snowplow mention to e2e docs

* tweak new snowplow doc page to be more in line with old section

* Update docs/developers-guide/e2e-tests.md

Co-authored-by: Uladzimir Havenchyk <125459446+uladzimirdev@users.noreply.github.com>

---------

Co-authored-by: Uladzimir Havenchyk <125459446+uladzimirdev@users.noreply.github.com>

docs/developers-guide/e2e-tests.md

@@ -149,9 +149,24 @@ yarn test-cypress-open-qa
 
 Tests that depend on Snowplow expect a running server. To run them, you need to:
 
-- run Snowplow locally: `docker-compose -f ./snowplow/docker-compose.yml up -d`
 - pass env variables to the test run: `MB_SNOWPLOW_AVAILABLE=true MB_SNOWPLOW_URL=http://localhost:9090 yarn test-cypress-open`
 
+## Testing with Snowplow
+Our end-to-end testing environment has been configured to run Snowplow Micro alongside the application.
+
+To run Snowplow locally use the following commands:
+
+```
+docker-compose -f ./snowplow/docker-compose.yml up -d
+export MB_SNOWPLOW_AVAILABLE=true
+export MB_SNOWPLOW_URL=http://localhost:9090
+```
+
+1. You can use `describeWithSnowplow` (or `describeWithSnowplowEE` for EE edition) method to define tests that only run when a Snowplow instance is running
+2. Use `resetSnowplow()` test helper before each test to clear the queue of processed events.
+3. Use `expectGoodSnowplowEvents(count)` to assert that events have been sent and processed correctly. Use `expectGoodSnowPlowEvent({ ...payload})` to assert on the content of a snowplow event
+4. Use `expectNoBadSnowplowEvents()` after each test to assert that no invalid events have been sent.
+
 ### Running tests that require SMTP server
 
 Some of our tests, that depend on the email being set up, require a local SMTP server. We use `maildev` Docker image for that purpose. At the time of this writing the image we use is `maildev/maildev:2.1.0`. It should be safe to always use the `:latest` image in your local development. Run this command: