Convert ActionCable tests from CoffeeScript to ES2015 and replace Blade with Karma and Rollup (#34440)

* Rename .coffee files in ActionCable test suite in prep for decaffeination

* Decaffeinate ActionCable tests

* Replace Blade with Karma and Rollup to run ActionCable JS tests

- Add karma and qunit devDependencies

- Add test script to ActionCable package

- Use rollup to bundle ActionCable tests

- Use karma as the ActionCable JS test runner

* Replace vendored mock-socket with package devDependency in ActionCable

* Move ActionCable yarn install to TravisCI before_install config

* Clean up decaffeinated ActionCable tests to use consistent formatting

1 files changed, 10 insertions, 0 deletions

diff --git a/actioncable/test/javascript/src/test_helpers/index.js b/actioncable/test/javascript/src/test_helpers/index.js
new file mode 100644
index 0000000000..5fa46c21ae
--- /dev/null
+++ b/actioncable/test/javascript/src/test_helpers/index.js
@@ -0,0 +1,10 @@
+import ActionCable from "../../../../app/javascript/action_cable/index"
+
+export const testURL = "ws://cable.example.com/"
+
+export function defer(callback) {
+  setTimeout(callback, 1)
+}
+
+const originalWebSocket = ActionCable.WebSocket
+QUnit.testDone(() => ActionCable.WebSocket = originalWebSocket)