Adding end-to-end tests

The first test is testing a tricky cache scenario with the back when testing variables.
The end-to-end package used is testcafe.

tests/package.json

@@ -0,0 +1,8 @@
+{
+  "devDependencies": {
+    "testcafe": "^1.17.1"
+  },
+  "scripts": {
+    "test": "testcafe"
+  }
+}