Add breaking-changes section to changelog (#530)

* add breaking-changes section to changelog

* Clean up parse_by_sections

* Thank you bastelfreak and ekohl!

spec/unit/generator/generator_generation_spec.rb

@@ -13,5 +13,61 @@ module GitHubChangelogGenerator
         end.not_to raise_error
       end
     end
+
+    describe "#parse_by_sections" do
+      def label(name)
+        { "name" => name }
+      end
+
+      def issue(title, labels)
+        { "title" => "issue #{title}", "labels" => labels.map { |l| label(l) } }
+      end
+
+      def pr(title, labels)
+        { "title" => "pr #{title}", "labels" => labels.map { |l| label(l) } }
+      end
+
+      def get_titles(issues)
+        issues.map { |issue| issue["title"] }
+      end
+
+      let(:options) do
+        {
+          bug_labels: ["bug"],
+          enhancement_labels: ["enhancement"],
+          breaking_labels: ["breaking"]
+        }
+      end
+
+      let(:issues) do
+        [
+          issue("no labels", []),
+          issue("enhancement", ["enhancement"]),
+          issue("bug", ["bug"]),
+          issue("breaking", ["breaking"]),
+          issue("all the labels", %w[enhancement bug breaking])
+        ]
+      end
+
+      let(:pull_requests) do
+        [
+          pr("no labels", []),
+          pr("enhancement", ["enhancement"]),
+          pr("bug", ["bug"]),
+          pr("breaking", ["breaking"]),
+          pr("all the labels", %w[enhancement bug breaking])
+        ]
+      end
+
+      it "works" do
+        sections = described_class.new(options).parse_by_sections(issues, pull_requests)
+
+        expect(get_titles(sections[:issues])).to eq(["issue no labels"])
+        expect(get_titles(sections[:enhancements])).to eq(["issue enhancement", "issue all the labels", "pr enhancement", "pr all the labels"])
+        expect(get_titles(sections[:bugs])).to eq(["issue bug", "pr bug"])
+        expect(get_titles(sections[:breaking])).to eq(["issue breaking", "pr breaking"])
+        expect(get_titles(pull_requests)).to eq(["pr no labels"])
+      end
+    end
   end
 end