WIP: Move test to cypress.io

This is mostly just a PoC to see if our CI infrastructure is able to run
cypress.io tests.

Changing language currently triggers a "500 Parse Error" in cypress,
which needs to be fixed in Cockpit.

cypress/plugins/index.js

@@ -0,0 +1,69 @@
+const child_process = require("child_process");
+
+var vm_proc, ssh_args, cockpit_url;
+
+// poor man's polling implementation
+function waitpid(pid) {
+    return new Promise((resolve, reject) => {
+        function check() {
+            try {
+                process.kill(pid);
+                // succeeds → process still exists, poll again
+                setTimeout(check, 50);
+            } catch(e) {
+                // ESRCH → process is gone
+                if (e.code == "ESRCH")
+                    resolve(null);
+                else
+                    throw e;
+            }
+        }
+
+        check();
+    });
+}
+
+module.exports = (on, config) => {
+    on("task", {
+        startVM: image => {
+            if (!image)
+                image = process.env.TEST_OS || "fedora-29";
+            // already running? happens when cypress restarts the test after visiting a baseUrl the first time
+            if (vm_proc)
+                return cockpit_url;
+
+            // no, start a new VM
+            return new Promise((resolve, reject) => {
+                let proc = child_process.spawn("bots/machine/testvm.py", [image],
+                                               { stdio: ["pipe", "pipe", "inherit"] });
+                let buf = "";
+                vm_proc = proc.pid;
+                proc.stdout.on("data", data => {
+                    buf += data.toString();
+                    if (buf.indexOf("\nRUNNING\n") > 0) {
+                        let lines = buf.split("\n");
+                        ssh_args = lines[0].split(" ").slice(1);
+                        cockpit_url = lines[1];
+                        resolve(cockpit_url);
+                    }
+                });
+                proc.on("error", err => reject (err));
+            });
+        },
+
+        stopVM: () => {
+            process.kill(vm_proc);
+            let p = waitpid(vm_proc);
+            p.then(() => { vm_proc = null; });
+            return p;
+        },
+
+        runVM: command => {
+            res = child_process.spawnSync("ssh", ssh_args.concat(command),
+                                          { stdio: ["pipe", "pipe", "inherit"], encoding: "UTF-8" });
+            if (res.status)
+                throw new Error(`Command "${command} failed with code ${res.status}`);
+            return res.stdout;
+        }
+    });
+}