migrate the negotiation example from koajs/koa and add test, refs koa…

…js#3.

negotiation/app.js

@@ -0,0 +1,82 @@
+
+var koa = require('koa');
+var app = module.exports = koa();
+
+var tobi = {
+  _id: '123',
+  name: 'tobi',
+  species: 'ferret'
+};
+
+var loki = {
+  _id: '321',
+  name: 'loki',
+  species: 'ferret'
+};
+
+var users = {
+  tobi: tobi,
+  loki: loki
+};
+
+// content negotiation middleware.
+// note that you should always check for
+// presence of a body, and sometimes you
+// may want to check the type, as it may
+// be a stream, buffer, string, etc.
+
+app.use(function *(next){
+  yield next;
+
+  // responses vary on accepted type
+  this.vary('Accept');
+  this.status = 'bad request';
+
+  // no body? nothing to format, early return
+  if (!this.body) return;
+
+  // accepts json, koa handles this for us,
+  // so just return
+  if (this.accepts('json')) return;
+
+  // accepts xml
+  if (this.accepts('xml')) {
+    this.type = 'xml';
+    this.body = '<name>' + this.body.name + '</name>';
+    return;
+  }
+
+  // accepts html
+  if (this.accepts('html')) {
+    this.type = 'html';
+    this.body = '<h1>' + this.body.name + '</h1>';
+    return;
+  }
+
+  // default to text
+  this.type = 'text';
+  this.body = this.body.name;
+});
+
+// filter responses, in this case remove ._id
+// since it's private
+
+app.use(function *(next){
+  yield next;
+
+  if (!this.body) return;
+
+  delete this.body._id;
+});
+
+// try $ GET /tobi
+// try $ GET /loki
+
+app.use(function *(){
+  var name = this.path.slice(1);
+  var user = users[name];
+  this.body = user;
+});
+
+if (!module.parent) app.listen(3000);
+

negotiation/test.js

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+var app = require('./app');
+var request = require('supertest').agent(app.listen());
+
+describe('negotiation', function() {
+  describe('json', function() {
+    it('should respond with json', function(done) {
+      request
+      .get('/tobi')
+      .set('Accept', 'application/json')
+      .expect(400)
+      .expect('vary', 'Accept')
+      .expect('Content-Type', /json/)
+      .expect({ name: 'tobi', species: 'ferret' }, done);
+    });
+  });
+
+  describe('xml', function() {
+    it('should respond with xml', function(done) {
+      request
+      .get('/tobi')
+      .set('Accept', 'application/xml')
+      .expect(400)
+      .expect('Content-Type', /xml/)
+      .expect('<name>tobi</name>', done);
+    });
+  });
+
+  describe('html', function() {
+    it('should respond with html', function(done) {
+      request
+      .get('/tobi')
+      .set('Accept', 'text/html')
+      .expect(400)
+      .expect('Content-Type', /html/)
+      .expect('<h1>tobi</h1>', done);
+    });
+  });
+
+  describe('text', function() {
+    it('should respond with html', function(done) {
+      request
+      .get('/tobi')
+      .set('Accept', 'text/plaino')
+      .expect(400)
+      .expect('Content-Type', /plain/)
+      .expect('tobi', done);
+    });
+  });
+});