Return 404 if deploy key cannot be found in Projects::DeployKeysController#disable

app/controllers/projects/deploy_keys_controller.rb

@@ -31,8 +31,10 @@ class Projects::DeployKeysController < Projects::ApplicationController
   end
 
   def disable
-    @project.deploy_keys_projects.find_by(deploy_key_id: params[:id]).destroy
+    deploy_key_project = @project.deploy_keys_projects.find_by(deploy_key_id: params[:id])
+    return render_404 unless deploy_key_project
 
+    deploy_key_project.destroy!
     redirect_to_repository_settings(@project)
   end
 

spec/features/projects/deploy_keys_spec.rb

+require 'spec_helper'
+
+describe 'Project deploy keys', feature: true do
+  let(:user) { create(:user) }
+  let(:project) { create(:project_empty_repo) }
+
+  before do
+    project.team << [user, :master]
+    login_as(user)
+  end
+
+  describe 'removing key' do
+    before do
+      create(:deploy_keys_project, project: project)
+    end
+
+    it 'removes association between project and deploy key' do
+      visit namespace_project_settings_repository_path(project.namespace, project)
+
+      page.within '.deploy-keys' do
+        expect { click_on 'Remove' }
+          .to change { project.deploy_keys.count }.by(-1)
+      end
+    end
+  end
+end