added specs for #content_type

spec/unit/request/content_type_spec.rb

@@ -0,0 +1,16 @@
+require 'spec_helper'
+
+describe Zero::Request, '#content_type' do
+  subject { Zero::Request.new(env) }
+
+  context 'returns nil with no content type' do
+    let(:env) { EnvGenerator.get('/foo') }
+    its('content_type') { should be(nil) }
+  end
+
+  context 'returns the set content type' do
+    let(:content_type) { 'bogus/type' }
+    let(:env) { EnvGenerator.post('/foo', {'CONTENT_TYPE' => content_type}) }
+    its('content_type') { should be(content_type) }
+  end
+end