test: integration tests (#40)

Co-authored-by: Gregor Martynus <39992+gr2m@users.noreply.github.com>

tests/README.md

@@ -0,0 +1,19 @@
+# Tests
+
+Add one test file per scenario. You can run them in isolation with:
+
+```bash
+node tests/post-token-set.test.js
+```
+
+All tests are run together in [tests/index.js](index.js), which can be execauted with ava
+
+```
+npx ava tests/index.js
+```
+
+or with npm
+
+```
+npm test
+```