Add Heroku CI smoke test (#238)

Author: Malax

test/spec/heroku_ci_spec.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require_relative 'spec_helper'
+
+RSpec.describe 'Maven buildpack' do
+  it 'runs tests on Heroku CI' do
+    app = Hatchet::Runner.new('simple-http-service')
+
+    app.run_ci do |test_run|
+      expect(clean_output(test_run.output)).to match(Regexp.new(<<~REGEX, Regexp::MULTILINE))
+        \\[INFO\\] -------------------------------------------------------
+        \\[INFO\\]  T E S T S
+        \\[INFO\\] -------------------------------------------------------
+        \\[INFO\\] Running com.heroku.AppTest
+        \\[INFO\\] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: [0-9\\.]+ s - in com.heroku.AppTest
+        \\[INFO\\] 
+        \\[INFO\\] Results:
+        \\[INFO\\] 
+        \\[INFO\\] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
+      REGEX
+    end
+  end
+end