docs: moar moar integration suite docs

docs/abra/hack.md

@@ -33,13 +33,31 @@ apt install bats bats-file bats-assert bats-support jq make git
 Then you can run the integration test suite with the following:
 
 ```
-export TEST_DOMAIN="test.example.com"
+export ABRA_TEST_DOMAIN="test.example.com"
 export ABRA_DIR="$HOME/.abra_test"
 bats tests/integration
 ```
 
-`TEST_DOMAIN` should also have a DNS A record for `*.test.example.com` which
+`ABRA_TEST_DOMAIN` should also have a DNS A record for `*.test.example.com`
-points to the same server so that the test suite can deploy apps freely.
+which points to the same server so that the test suite can deploy apps freely.
+
+If you're hacking on the tests, you can speed things up with the following.
+
+```
+export ABRA_SKIP_TEARDOWN=1
+```
+
+This will avoid nuking `$ABRA_DIR` for each test which avoids the costly `git
+clone` of the catalogue on each test run. For the actual CI testing, we
+probably want this clean slate on each test to avoid confusion.
+
+You can filter on test names and/or tags to run specific kinds of tests.
+
+```
+bats tests/integration \
+  --filter "validate app argument" \
+  --filter-tags "app_backup,\!slow"
+```
 
 ## Using the `abra` public API