Make the dry_run action accept an event payload

app/controllers/agents_controller.rb

@@ -50,7 +50,13 @@ class AgentsController < ApplicationController
     agent.name ||= '(Untitled)'
 
     if agent.valid?
-      results = agent.dry_run!
+      if event_payload = params[:event]
+        dummy_agent = Agent.build_for_type('ManualEventAgent', current_user, name: 'Dry-Runner')
+        dummy_agent.readonly!
+        event = dummy_agent.events.build(user: current_user, payload: event_payload)
+      end
+
+      results = agent.dry_run!(event)
 
       render json: {
         log: results[:log],

spec/controllers/agents_controller_spec.rb

@@ -377,6 +377,19 @@ describe AgentsController do
         [users(:bob).agents.count, users(:bob).events.count, users(:bob).logs.count, agent.name, agent.updated_at]
       }
     end
+
+    it "accepts an event" do
+      sign_in users(:bob)
+      agent = agents(:bob_website_agent)
+      url_from_event = "http://xkcd.com/?from_event=1".freeze
+      expect {
+        post :dry_run, id: agent, event: { url: url_from_event }
+      }.not_to change {
+        [users(:bob).agents.count, users(:bob).events.count, users(:bob).logs.count, agent.name, agent.updated_at]
+      }
+      json = JSON.parse(response.body)
+      expect(json['log']).to match(/^I, .* : Fetching #{Regexp.quote(url_from_event)}$/)
+    end
   end
 
   describe "DELETE memory" do