'The keyword portion of an RVKC should still be case-insensitive, but
the field-specifier portion should be case-sensitive.'

def test_field_specifier_case_senstivity(self):

    header = fits.Header()
    header.set('abc.def', 1)
    header.set('abc.DEF', 2)
    assert (header['abc.def'] == 1)
    assert (header['ABC.def'] == 1)
    assert (header['aBc.def'] == 1)
    assert (header['ABC.DEF'] == 2)
    assert ('ABC.dEf' not in header)
