it('converts the name to lowercase', function () {
   const rawRes = {headers: {hello: 'world'}};
   const res = new SyntheticResponse(rawRes, {});
   expect(res.getHeader('Hello')).to.equal(res.getHeader('hello'));
 });
 it('intercepts content-type headers', function () {
   const rawRes = {contentType: 'application/x-meow'};
   const res = new SyntheticResponse(rawRes, {});
   expect(res.getHeader('content-type')).to.equal(rawRes.contentType);
 });
 it('returns the header by name', function () {
   const rawRes = {headers: {hello: 'world'}};
   const res = new SyntheticResponse(rawRes, {});
   expect(res.getHeader('hello')).to.equal('world');
 });