Add basic feature test for problem browsing (#300)

This page relies on a lot of ApplicationPresenter / StrongPresenter
features which I am trying to write out, so seemed worthwhile having a
small test for faster iterate.

Author: bagedevimo

spec/features/problem_browsing_spec.rb

@@ -0,0 +1,19 @@
+require "spec_helper"
+
+feature "Problem browsing" do
+  let(:user) { FactoryBot.create(:superadmin) }
+  let!(:problem) { FactoryBot.create(:problem) }
+
+  scenario "Admin browses and view problems" do
+    login_as user, scope: :user
+
+    visit "/problems"
+
+    headers = find(".main_table > thead > tr").all("th").map(&:text)
+    rows = find(".main_table > tbody").all("tr").map { |r| r.all("td").map(&:text) }
+    expect(headers).to eq(["", "Name", "Input", "Output", "Memory Limt", "Time Limit", "Owner", "Progress", "", ""])
+    expect(rows.length).to eq(Problem.count)
+
+    expect(rows[0]).to eq(["", problem.name, problem.input, problem.output, "1 MB", "1.0 s", "System", "", "Edit", "Destroy"])
+  end
+end