public void Expires_ReadAndWriteProperty_ValueMatchesPriorSetValue()
{
Assert.Null(_headers.Expires);
DateTimeOffset expected = DateTimeOffset.Now;
_headers.Expires = expected;
Assert.Equal(expected, _headers.Expires);
_headers.Expires = null;
Assert.Null(_headers.Expires);
Assert.False(_headers.Contains("Expires"));
}