add one view test

spec/views/map_activity_mailer/daily_summary.html.erb_spec.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'map_activity_mailer/daily_summary.html.erb' do
+  it 'displays messages sent' do
+    assign(:user, create(:user))
+    assign(:map, create(:map))
+    assign(:summary_data, stats: {
+             messages_sent: 5
+           })
+
+    render
+
+    expect(rendered).to match(/5 messages/)
+  end
+end