Add test

spec/post_spec.rb

@@ -8,6 +8,7 @@
   let(:timestamp) { Time.now.strftime(Jekyll::Compose::DEFAULT_TIMESTAMP_FORMAT) }
   let(:filename) { "#{datestamp}-a-test-post.md" }
   let(:path) { posts_dir.join(filename) }
+  let(:jekyll_config) { YAML.load_file('../fixtures/_config.yml') }
 
   before(:all) do
     FileUtils.mkdir_p source_dir unless File.directory? source_dir
@@ -49,6 +50,13 @@
     expect(File.read(path)).to match(%r!layout: other-layout!)
   end
 
+  it 'creates a new page with the specified config' do
+    expect(Jekyll).to receive(:configuration).and_return(jekyll_config)
+    capture_stdout { described_class.process(args) }
+    expect(File.read(path)).to match(/description: my description/)
+    expect(File.read(path)).to match(/category: /)
+  end
+
   it "should write a helpful message when successful" do
     output = capture_stdout { described_class.process(args) }
     expect(output).to include("New post created at _posts/#{filename}.")