def test_default_headers_case_insensitive(httpbin):
    """
    <https://github.com/httpie/cli/issues/644>
    """
    r = http(
        '--debug',
        '--print=H',
        httpbin + '/post',
        'CONTENT-TYPE:application/json-patch+json',
        'a=b',
    )
    assert 'CONTENT-TYPE: application/json-patch+json' in r
    assert 'Content-Type' not in r

    <https://github.com/httpie/cli/issues/644>
    
tests/test_defaults.py