Fix billing page regression when trial ends

Fixes a regression which appeared since august 16, 2019.
Users on trial can't access their personal or group billing pages
after their trials expire. Adds tests for the trial views.
Added view tests as trial flow is business critical

changelogs/unreleased/31364-error-when-attempting-to-view-gitlab-com-group-billing-page.yml

+---
+title: Fix error when viewing group billing page
+merge_request: 18740
+author:
+type: fixed

ee/app/views/shared/billings/_trial_status.html.haml

 - faq_link          = link_to s_("BillingPlans|frequently asked questions"), "https://about.gitlab.com/gitlab-com/#faq"
 - pricing_page_link = link_to s_("BillingPlans|Pricing page"), "https://about.gitlab.com/pricing"
 - features_link     = link_to s_("BillingPlans|features"), "https://about.gitlab.com/features"
+- learn_more_text = s_("BillingPlans|Learn more about each plan by reading our %{faq_link}.").html_safe % { faq_link: faq_link }
 
 - if namespace.eligible_for_trial?
   = s_("BillingPlans|Learn more about each plan by reading our %{faq_link}, or start a free 30-day trial of GitLab.com Gold.").html_safe % { faq_link: faq_link }

ee/spec/views/shared/billings/_trial_status.html.haml_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'shared/billings/_trial_status.html.haml' do
+  include ApplicationHelper
+
+  let(:group) { create(:group) }
+  let(:gitlab_subscription) { create(:gitlab_subscription, namespace: group) }
+  let(:plan) { nil }
+  let(:trial_ends_on) { nil }
+  let(:trial) { false }
+
+  before do
+    gitlab_subscription.update(
+      hosted_plan: plan,
+      trial_ends_on: trial_ends_on,
+      trial: trial
+    )
+  end
+
+  context 'when not eligible for trial' do
+    it 'offers to learn more about plans' do
+      render 'shared/billings/trial_status', namespace: group
+      expect(rendered).to have_content("Learn more about each plan by visiting our")
+    end
+  end
+
+  context 'when trial active' do
+    let(:plan) { create(:bronze_plan) }
+    let(:trial_ends_on) { Date.tomorrow }
+    let(:trial) { true }
+
+    it 'displays expiry date' do
+      render 'shared/billings/trial_status', namespace: group
+      expect(rendered).to have_content("Your GitLab.com trial will expire after #{trial_ends_on}")
+    end
+  end
+
+  context 'when trial expired' do
+    let(:plan) { create(:free_plan) }
+    let(:trial_ends_on) { Date.yesterday }
+
+    it 'displays the date is expired' do
+      render 'shared/billings/trial_status', namespace: group
+      expect(rendered).to have_content("Your GitLab.com trial expired on #{trial_ends_on}")
+    end
+  end
+
+  context 'when eligible for trial' do
+    before do
+      allow(::Gitlab).to receive(:com?).and_return(true)
+    end
+
+    it 'offers a trial' do
+      render 'shared/billings/trial_status', namespace: group
+      expect(rendered).to have_content("start a free 30-day trial of GitLab.com Gold")
+    end
+  end
+end

locale/gitlab.pot

@@ -2415,6 +2415,9 @@ msgstr ""
 msgid "BillingPlans|Learn more about each plan by reading our %{faq_link}, or start a free 30-day trial of GitLab.com Gold."
 msgstr ""
 
+msgid "BillingPlans|Learn more about each plan by reading our %{faq_link}."
+msgstr ""
+
 msgid "BillingPlans|Learn more about each plan by visiting our %{pricing_page_link}."
 msgstr ""