public function testNormalizeKey()
 {
     $h = new Headers();
     $this->assertEquals('foo-bar', $h->normalizeKey('HTTP_FOO_BAR'));
     $this->assertEquals('foo-bar', $h->normalizeKey('HTTP-FOO-BAR'));
     $this->assertEquals('foo-bar', $h->normalizeKey('Http-Foo-Bar'));
     $this->assertEquals('foo-bar', $h->normalizeKey('Http_Foo_Bar'));
     $this->assertEquals('foo-bar', $h->normalizeKey('http_foo_bar'));
     $this->assertEquals('foo-bar', $h->normalizeKey('http-foo-bar'));
 }