diff --git a/docs/abra/hack.md b/docs/abra/hack.md
index fa0e47fb..904e11fa 100644
--- a/docs/abra/hack.md
+++ b/docs/abra/hack.md
@@ -59,6 +59,23 @@ It's advised that you re-use the same server and therefore the same Traefik
 deployment for running your integration tests. The test suite does not deploy
 Traefik for you. Then you'll have more stable results.
 
+### Tagging tests
+
+When a test actually deploys something to a server, we tag it with the following:
+
+```
+# bats test_tags=slow
+@test "..." {
+  ...
+}
+```
+
+Then we can use [filters](#filter-tests) (see below) to pick out a subset of
+tests which do/do not use a live server. Feel free to come up with your own
+tags. See the `bats-core`
+[docs](https://bats-core.readthedocs.io/en/stable/writing-tests.html#tagging-tests)
+for more.
+
 ### Filter tests
 
 You can filter on test names to run specific kinds of tests.