'Test appending a new card with just the keyword, and no value or
comment given.'

def test_header_append_keyword_only(self):

    header = fits.Header([('A', 'B'), ('C', 'D')])
    header.append('E')
    assert (len(header) == 3)
    assert (list(header)[(-1)] == 'E')
    assert (header[(-1)] == '')
    assert (header.comments['E'] == '')
    header.append('')
    assert (len(header) == 4)
    assert (list(header)[(-1)] == '')
    assert (header[''] == '')
    assert (header.comments[''] == '')
