From #21995 (comment), @seberg writes

Way too long, but test_multiarray.py with TestCreation might be an option. Otherwise test_array_coercion.py has somewhat related tests so you could just add it in that file. The only real problem here is that it doesn't belong under array_api/tests, but core/tests

... test_array_coercion.py has somewhat related tests so you could just add it in that file.

If you think test_array_coercion.py is appropriate, that looks like the best fit to me.

Will do.

Interesting, the windows RuntimeWarning heisenbug seems to be affecting the Linux 32bit full-with-asserts runner here:

_________________ TestMatmulOperator.test_vector_matrix_values _________________

self = <numpy.core.tests.test_multiarray.TestMatmulOperator object at 0xe7991bc8>

    def test_vector_matrix_values(self):
        vec = np.array([1, 2])
        mat1 = np.array([[1, 2], [3, 4]])
        mat2 = np.stack([mat1]*2, axis=0)
        tgt1 = np.array([7, 10])
        tgt2 = np.stack([tgt1]*2, axis=0)
        for dt in self.types[1:]:
            v = vec.astype(dt)
            m1 = mat1.astype(dt)
            m2 = mat2.astype(dt)
>           res = self.matmul(v, m1)
E           RuntimeWarning: invalid value encountered in matmul

Not a worry for this, but might be interesting and make debugging easier, eventually?

Thanks @eirrgang, somehow I thought I had a closer look at this during SciPy already... Could in principle split up the test into smaller ones, but it doesn't matter much and the test looks very thorough.