Repository: scipy/scipy
File: scipy/signal/tests/test_signaltools.py (Python)

Code before:
        b = np.arange(-6, 0).reshape((3, 2))

        assert_raises(ValueError, signal.correlate2d, *(a, b), **{'mode': 'valid'})
        assert_raises(ValueError, signal.correlate2d, *(b, a), **{'mode': 'valid'})

    @make_xp_test_case(signal.correlate2d)
    def test_complex_input(self, xp):
        xp_assert_equal(signal.correlate2d(xp.asarray([[1]]), xp.asarray([[2j]])),
                        xp.asarray([-2j]), check_shape=False, check_dtype=False)
        xp_assert_equal(signal.correlate2d(xp.asarray([[2j]]), xp.asarray([[3j]])),
                        xp.asarray([6+0j]), check_shape=False, check_dtype=False)
        xp_assert_equal(signal.correlate2d(xp.asarray([[3j]]), xp.asarray([[4]])),
                        xp.asarray([12j]), check_shape=False, check_dtype=False)


@make_xp_test_case(lfilter_zi)
class TestLFilterZI:

    def test_exceptions(self, xp):
        """Raise all exceptions in `lfilter_zi`. """
        with pytest.raises(ValueError, match="^Numerator `b` and Denominator `a` must"):
             lfilter_zi(b=xp.eye(3), a=1)  # b must be 1-d array
        with pytest.raises(ValueError, match="^Numerator `b` and Denominator `a` must"):
             lfilter_zi(b=1, a=xp.eye(3))  # a must be 1-d array
        with pytest.raises(ValueError, match="^First coefficient of parameter `a` "):
            lfilter_zi(b=1, a=[0, 0, 0])
        with pytest.raises(ValueError, match="^Filter not stable due to sum"):
            lfilter_zi(b=1, a=[-1, 1, -2, 2])

    @skip_xp_backends(np_only=True, reason='list inputs are numpy specific')
    def test_array_like(self, xp):
        zi_expected = xp.asarray([5.0, -1.0])
        zi = lfilter_zi([1.0, 0.0, 2.0], [1.0, -1.0, 0.5])
        assert_array_almost_equal(zi, zi_expected)

    @skip_xp_backends("dask.array", reason="FutureWarning emitted")
    @pytest.mark.parametrize('b, a, zi_expected,',[
        ([1., 0., 2.],     [1., -1., 0.5],   [5., -1.]),
        ([1., 2., 3., 4.], [1.,],            [9.,  7.,  4.]),
        ([1., 9.],         [1., 2., 3., 4.], [0. ,-7., -4.])])
    def test_basic(self, b, a, zi_expected, xp):
        b, a, zi_expected = (xp.asarray(v_) for v_ in (b, a, zi_expected))

        zi = lfilter_zi(b, a)
        assert_array_almost_equal(zi, zi_expected)

        y = lfilter(b, a, xp.ones(9), zi=zi)[0]  # test for constant filter response
        y_expected = xp.full_like(y, fill_value=sum(b)/sum(a))
        assert_array_almost_equal(y, y_expected)

    def test_scale_invariance(self, xp):

Review comment (suggestion):
```suggestion
            lfilter_zi(b=1, a=xp.asarray([0, 0, 0]))
```

Code after:
        b = np.arange(-6, 0).reshape((3, 2))

        assert_raises(ValueError, signal.correlate2d, *(a, b), **{'mode': 'valid'})
        assert_raises(ValueError, signal.correlate2d, *(b, a), **{'mode': 'valid'})

    @make_xp_test_case(signal.correlate2d)
    def test_complex_input(self, xp):
        xp_assert_equal(signal.correlate2d(xp.asarray([[1]]), xp.asarray([[2j]])),
                        xp.asarray([-2j]), check_shape=False, check_dtype=False)
        xp_assert_equal(signal.correlate2d(xp.asarray([[2j]]), xp.asarray([[3j]])),
                        xp.asarray([6+0j]), check_shape=False, check_dtype=False)
        xp_assert_equal(signal.correlate2d(xp.asarray([[3j]]), xp.asarray([[4]])),
                        xp.asarray([12j]), check_shape=False, check_dtype=False)


@make_xp_test_case(lfilter_zi)
class TestLFilterZI:

    def test_exceptions(self, xp):
        """Raise all exceptions in `lfilter_zi`. """
        with pytest.raises(ValueError, match="^Numerator `b` and Denominator `a` must"):
             lfilter_zi(b=xp.eye(3), a=1)  # b must be 1-d array
        with pytest.raises(ValueError, match="^Numerator `b` and Denominator `a` must"):
             lfilter_zi(b=1, a=xp.eye(3))  # a must be 1-d array
        with pytest.raises(ValueError, match="^First coefficient of parameter `a` "):
            lfilter_zi(b=1, a=xp.asarray([0, 0, 0]))
        with pytest.raises(ValueError, match="^Filter not stable due to sum"):
            lfilter_zi(b=1, a=xp.asarray([-1, 1, -2, 2]))

    @skip_xp_backends(np_only=True, reason='list inputs are numpy specific')
    def test_array_like(self, xp):
        zi_expected = xp.asarray([5.0, -1.0])
        zi = lfilter_zi([1.0, 0.0, 2.0], [1.0, -1.0, 0.5])
        assert_array_almost_equal(zi, zi_expected)

    @skip_xp_backends("dask.array", reason="FutureWarning emitted")
    @pytest.mark.parametrize('b, a, zi_expected,',[
        ([1., 0., 2.],     [1., -1., 0.5],   [5., -1.]),
        ([1., 2., 3., 4.], [1.,],            [9.,  7.,  4.]),
        ([1., 9.],         [1., 2., 3., 4.], [0. ,-7., -4.])])
    def test_basic(self, b, a, zi_expected, xp):
        b, a, zi_expected = (xp.asarray(v_) for v_ in (b, a, zi_expected))

        zi = lfilter_zi(b, a)
        assert_array_almost_equal(zi, zi_expected)

        y = lfilter(b, a, xp.ones(9), zi=zi)[0]  # test for constant filter response
        y_expected = xp.full_like(y, fill_value=sum(b)/sum(a))
        assert_array_almost_equal(y, y_expected)

    def test_scale_invariance(self, xp):