add tests for controllers and ActionCable channels; improve main backend docs

main-server/spec/requests/api/registrations_spec.rb

@@ -0,0 +1,52 @@
+require "rails_helper"
+
+RSpec.describe "Registrations API", type: :request do
+  describe "POST /api/register" do
+    let(:valid_attributes) do
+      {
+        user: {
+          nickname: "Sinbad",
+          password: "password123"
+        }
+      }
+    end
+
+    context "with valid parameters" do
+      it "registers a new user and returns 201 Created with token" do
+        expect {
+          post "/api/register", params: valid_attributes, as: :json
+        }.to change(User, :count).by(1)
+
+        expect(response).to have_http_status(:created)
+        json = JSON.parse(response.body)
+
+        expect(json["token"]).to be_present
+        expect(json["user"]["nickname"]).to eq("Sinbad")
+        expect(json["user"]["id"]).to eq(User.last.id)
+        expect(json["user"]["avatar_url"]).to be_nil
+        expect(json["user"]["created_at"]).to be_present
+      end
+    end
+
+    context "with invalid parameters" do
+      it "returns 422 Unprocessable Content when nickname is taken" do
+        User.create!(nickname: "Sinbad", password: "password123")
+
+        post "/api/register", params: valid_attributes, as: :json
+
+        expect(response).to have_http_status(422)
+        json = JSON.parse(response.body)
+        expect(json["errors"]).to include("Nickname has already been taken")
+      end
+
+      it "returns 422 Unprocessable Content when password is too short" do
+        invalid_attrs = { user: { nickname: "Sinbad", password: "123" } }
+        post "/api/register", params: invalid_attrs, as: :json
+
+        expect(response).to have_http_status(422)
+        json = JSON.parse(response.body)
+        expect(json["errors"]).to include("Password is too short (minimum is 6 characters)")
+      end
+    end
+  end
+end