Original implementation to allow users to subscribe to labels

1. Allow subscribing (the current user) to a label

- Refactor the `Subscription` coffeescript class
  - The main change is that it accepts a container, and conducts all
    DOM queries within its scope. We need this because the labels
    page has multiple instances of `Subscription` on the same page.

2. Creating an issue or MR with labels notifies users subscribed to those labels

- Label `has_many` subscribers through subscriptions.

3. Adding a label to an issue or MR notifies users subscribed to those labels

- This only applies to subscribers of the label that has just been
  added, not all labels for the issue.

1 files changed, 16 insertions, 0 deletions

diff --git a/spec/models/concerns/subscribable_spec.rb b/spec/models/concerns/subscribable_spec.rb
new file mode 100644
index 00000000000..9ee60426a5d
--- /dev/null
+++ b/spec/models/concerns/subscribable_spec.rb
@@ -0,0 +1,16 @@
+require "spec_helper"
+
+describe Subscribable, "Subscribable" do
+  let(:resource) { create(:issue) }
+  let(:user) { create(:user) }
+
+  describe "#subscribed?" do
+    it do
+      expect(resource.subscribed?(user)).to be_falsey
+      resource.toggle_subscription(user)
+      expect(resource.subscribed?(user)).to be_truthy
+      resource.toggle_subscription(user)
+      expect(resource.subscribed?(user)).to be_falsey
+    end
+  end
+end