Add tests for OrganisationNameChangesController actions

spec/controllers/organisation_name_changes_controller_spec.rb

@@ -0,0 +1,46 @@
+require "rails_helper"
+
+RSpec.describe OrganisationNameChangesController, type: :controller do
+  let(:organisation) { create(:organisation) }
+
+  describe "GET #change_name" do
+    it "assigns previous name changes" do
+      create(:organisation_name_change, organisation:, name: "Old Name", startdate: 1.day.ago)
+      get :change_name, params: { id: organisation.id }
+      expect(controller.instance_variable_get(:@previous_name_changes)).to eq(organisation.name_changes_with_dates)
+    end
+  end
+
+  describe "POST #create" do
+    let(:params) do
+      {
+        organisation_name_change: {
+          name: "New Name",
+          startdate: 1.day.from_now,
+          immediate_change: false,
+        },
+      }
+    end
+
+    it "creates a new organisation name change with valid params" do
+      expect {
+        post :create, params: { id: organisation.id }.merge(params)
+      }.to change(OrganisationNameChange, :count).by(1)
+
+      expect(response).to redirect_to(organisation_path(organisation))
+      expect(flash[:notice]).to eq("Name change scheduled for #{1.day.from_now.to_date.to_formatted_s(:govuk_date)}.")
+    end
+
+    it "creates an immediate name change when immediate_change is true" do
+      params[:organisation_name_change][:immediate_change] = true
+      params[:organisation_name_change].delete(:startdate)
+
+      expect {
+        post :create, params: { id: organisation.id }.merge(params)
+      }.to change(OrganisationNameChange, :count).by(1)
+
+      expect(response).to redirect_to(organisation_path(organisation))
+      expect(flash[:notice]).to eq("Name change saved successfully.")
+    end
+  end
+end