def test_string_types(self):
        """
        Test from_dtype() and as_dtype() with the character string types.
        """
        def check(typestring, numba_type):
            # Only native ordering and alignment is supported
            dtype = np.dtype(typestring)
            self.assertEqual(numpy_support.from_dtype(dtype), numba_type)
            self.assertEqual(dtype, numpy_support.as_dtype(numba_type))

        check('S10', types.CharSeq(10))
        check('a11', types.CharSeq(11))
        check('U12', types.UnicodeCharSeq(12))

        Test from_dtype() and as_dtype() with the character string types.
        
numba/tests/test_numpy_support.py