add missing test helper fn

test/lib/departures.js

@@ -0,0 +1,21 @@
+'use strict'
+
+const co = require('./co')
+
+const testDepartures = co(function* (cfg) {
+	const {test: t, departures: deps, validate, id} = cfg
+
+	validate(t, deps, 'departures', 'departures')
+	t.ok(deps.length > 0, 'must be >0 departures')
+	for (let i = 0; i < deps.length; i++) {
+		const dep = deps[i]
+		const name = `deps[${i}]`
+
+		t.equal(dep.station.id, id, name + '.station.id is invalid')
+	}
+
+	// todo: move into deps validator
+	t.deepEqual(deps, deps.sort((a, b) => t.when > b.when))
+})
+
+module.exports = testDepartures