add: unit and integration testing

app/node_modules/collect-v8-coverage/README.md

@@ -0,0 +1,15 @@
+# collect-v8-coverage
+
+Use this module to start and stop the V8 inspector manually and collect precise coverage.
+
+```js
+const {CoverageInstrumenter} = require('collect-v8-coverage');
+
+const instrumenter = new CoverageInstrumenter();
+
+await instrumenter.startInstrumenting();
+
+// require some modules, run some code
+
+const coverage = await instrumenter.stopInstrumenting();
+```