Adds ExportCsvWorker spec

spec/workers/export_csv_worker_spec.rb

+require 'spec_helper'
+
+describe ExportCsvWorker do
+  let(:user) { create(:user) }
+  let(:project) { create(:empty_project, creator: user) }
+
+  def perform(params = {})
+    described_class.new.perform(user.id, project.id, params)
+  end
+
+  it 'emails a CSV' do
+    expect{perform}.to change(ActionMailer::Base.deliveries, :size).by(1)
+  end
+
+  it 'ensures that project_id is passed to issues_finder' do
+    expect(IssuesFinder).to receive(:new).with(anything, hash_including(project_id: project.id)).and_call_original
+
+    perform
+  end
+
+  it 'converts controller string keys to symbol keys for IssuesFinder' do
+    expect(IssuesFinder).to receive(:new).with(anything, hash_including(test_key: true)).and_call_original
+
+    perform('test_key' => true)
+  end
+end