# The purpose of these tests are to ensure that calling ufuncs with quantities
# returns quantities with the right units, or raises exceptions.

import concurrent.futures
import dataclasses
import warnings
from collections import namedtuple

import numpy as np
import pytest
from erfa import ufunc as erfa_ufunc
from numpy.testing import assert_allclose, assert_array_equal

from astropy import units as u
from astropy.units import quantity_helper as qh
from astropy.units.quantity_helper.converters import UfuncHelpers
from astropy.units.quantity_helper.helpers import helper_sqrt
from astropy.utils.compat.optional_deps import HAS_SCIPY

testcase = namedtuple("testcase", ["f", "q_in", "q_out"])
testexc = namedtuple("testexc", ["f", "q_in", "exc", "msg"])
testwarn = namedtuple("testwarn", ["f", "q_in", "wfilter"])


@pytest.mark.skip
def test_testcase(tc):
    results = tc.f(*tc.q_in)
    # careful of the following line, would break on a function returning
    # a single tuple (as opposed to tuple of return values)
    results = (results,) if not isinstance(results, tuple) else results
    for result, expected in zip(results, tc.q_out):
        assert result.unit == expected.unit
        assert_allclose(result.value, expected.value, atol=1.0e-15)


@pytest.mark.skip
def test_testexc(te):
    with pytest.raises(te.exc) as exc:
        te.f(*te.q_in)
    if te.msg is not None:
        assert te.msg in exc.value.args[0]


@pytest.mark.skip
def test_testwarn(tw):
    with warnings.catch_warnings():
        warnings.filterwarnings(tw.wfilter)
        tw.f(*tw.q_in)


class TestUfuncHelpers:
    # Note that this test should work even if scipy is present, since
    # the scipy.special ufuncs are only loaded on demand.
    # The test passes independently of whether erfa is already loaded
    # (which will be the case for a full test, since coordinates uses it).
    def test_coverage(self):
        """Test that we cover all ufunc's"""

        all_np_ufuncs = {
            ufunc
            for ufunc in np.core.umath.__dict__.values()
            if isinstance(ufunc, np.ufunc)
        }

        all_q_ufuncs = qh.UNSUPPORTED_UFUNCS | set(qh.UFUNC_HELPERS.keys())
        # Check that every numpy ufunc is covered.
        assert all_np_ufuncs - all_q_ufuncs == set()
        # Check that all ufuncs we cover come from numpy or erfa.
        # (Since coverage for erfa is incomplete, we do not check
        # this the other way).
        all_erfa_ufuncs = {
            ufunc
            for ufunc in erfa_ufunc.__dict__.values()
            if isinstance(ufunc, np.ufunc)
        }
        assert all_q_ufuncs - all_np_ufuncs - all_erfa_ufuncs == set()

    def test_scipy_registered(self):
        # Should be registered as existing even if scipy is not available.
        assert "scipy.special" in qh.UFUNC_HELPERS.modules

    def test_removal_addition(self):
        assert np.add in qh.UFUNC_HELPERS
        assert np.add not in qh.UNSUPPORTED_UFUNCS
        qh.UFUNC_HELPERS[np.add] = None
        assert np.add not in qh.UFUNC_HELPERS
        assert np.add in qh.UNSUPPORTED_UFUNCS
        qh.UFUNC_HELPERS[np.add] = qh.UFUNC_HELPERS[np.subtract]
        assert np.add in qh.UFUNC_HELPERS
        assert np.add not in qh.UNSUPPORTED_UFUNCS

    @pytest.mark.slow
    def test_thread_safety(self, fast_thread_switching):
        def dummy_ufunc(*args, **kwargs):
            return np.sqrt(*args, **kwargs)

        def register():
            return {dummy_ufunc: helper_sqrt}

        workers = 8
        with concurrent.futures.ThreadPoolExecutor(max_workers=workers) as executor:
            for p in range(10000):
                helpers = UfuncHelpers()
                helpers.register_module(
                    "astropy.units.tests.test_quantity_ufuncs",
                    ["dummy_ufunc"],
                    register,
                )
                futures = [
                    executor.submit(lambda: helpers[dummy_ufunc])
                    for i in range(workers)
                ]
                values = [future.result() for future in futures]
                assert values == [helper_sqrt] * workers


class TestQuantityTrigonometricFuncs:
    """
    Test trigonometric functions
    """

    @pytest.mark.parametrize(
        "tc",
        (
            testcase(
                f=np.sin,
                q_in=(30.0 * u.degree,),
                q_out=(0.5 * u.dimensionless_unscaled,),
            ),
            testcase(
                f=np.sin,
                q_in=(np.array([0.0, np.pi / 4.0, np.pi / 2.0]) * u.radian,),
                q_out=(np.array([0.0, 1.0 / np.sqrt(2.0), 1.0]) * u.one,),
            ),
            testcase(
                f=np.arcsin,
                q_in=(np.sin(30.0 * u.degree),),
                q_out=(np.radians(30.0) * u.radian,),
            ),
            testcase(
                f=np.arcsin,
                q_in=(np.sin(np.array([0.0, np.pi / 4.0, np.pi / 2.0]) * u.radian),),
                q_out=(np.array([0.0, np.pi / 4.0, np.pi / 2.0]) * u.radian,),
            ),
            testcase(
                f=np.cos,
                q_in=(np.pi / 3.0 * u.radian,),
                q_out=(0.5 * u.dimensionless_unscaled,),
            ),
            testcase(
                f=np.cos,
                q_in=(np.array([0.0, np.pi / 4.0, np.pi / 2.0]) * u.radian,),
                q_out=(np.array([1.0, 1.0 / np.sqrt(2.0), 0.0]) * u.one,),
            ),
            testcase(
                f=np.arccos,
                q_in=(np.cos(np.pi / 3.0 * u.radian),),
                q_out=(np.pi / 3.0 * u.radian,),
            ),
            testcase(
                f=np.arccos,
                q_in=(np.cos(np.array([0.0, np.pi / 4.0, np.pi / 2.0]) * u.radian),),
                q_out=(np.array([0.0, np.pi / 4.0, np.pi / 2.0]) * u.radian,),
            ),
            testcase(
                f=np.tan,
                q_in=(np.pi / 3.0 * u.radian,),
                q_out=(np.sqrt(3.0) * u.dimensionless_unscaled,),
            ),
            testcase(
                f=np.tan,
                q_in=(np.array([0.0, 45.0, 135.0, 180.0]) * u.degree,),
                q_out=(np.array([0.0, 1.0, -1.0, 0.0]) * u.dimensionless_unscaled,),
            ),
            testcase(
                f=np.arctan,
                q_in=(np.tan(np.pi / 3.0 * u.radian),),
                q_out=(np.pi / 3.0 * u.radian,),
            ),
            testcase(
                f=np.arctan,
                q_in=(np.tan(np.array([10.0, 30.0, 70.0, 80.0]) * u.degree),),
                q_out=(np.radians(np.array([10.0, 30.0, 70.0, 80.0]) * u.degree),),
            ),
            testcase(
                f=np.arctan2,
                q_in=(np.array([10.0, 30.0, 70.0, 80.0]) * u.m, 2.0 * u.km),
                q_out=(
                    np.arctan2(np.array([10.0, 30.0, 70.0, 80.0]), 2000.0) * u.radian,
                ),
            ),
            testcase(
                f=np.arctan2,
                q_in=((np.array([10.0, 80.0]) * u.m / (2.0 * u.km)).to(u.one), 1.0),
                q_out=(np.arctan2(np.array([10.0, 80.0]) / 2000.0, 1.0) * u.radian,),
            ),
            testcase(f=np.deg2rad, q_in=(180.0 * u.degree,), q_out=(np.pi * u.radian,)),
            testcase(f=np.radians, q_in=(180.0 * u.degree,), q_out=(np.pi * u.radian,)),
            testcase(f=np.deg2rad, q_in=(3.0 * u.radian,), q_out=(3.0 * u.radian,)),
            testcase(f=np.radians, q_in=(3.0 * u.radian,), q_out=(3.0 * u.radian,)),
            testcase(f=np.rad2deg, q_in=(60.0 * u.degree,), q_out=(60.0 * u.degree,)),
            testcase(f=np.degrees, q_in=(60.0 * u.degree,), q_out=(60.0 * u.degree,)),
            testcase(f=np.rad2deg, q_in=(np.pi * u.radian,), q_out=(180.0 * u.degree,)),
            testcase(f=np.degrees, q_in=(np.pi * u.radian,), q_out=(180.0 * u.degree,)),
        ),
    )
    def test_testcases(self, tc):
        return test_testcase(tc)

    @pytest.mark.parametrize(
        "te",
        (
            testexc(f=np.deg2rad, q_in=(3.0 * u.m,), exc=TypeError, msg=None),
            testexc(f=np.radians, q_in=(3.0 * u.m,), exc=TypeError, msg=None),
            testexc(f=np.rad2deg, q_in=(3.0 * u.m), exc=TypeError, msg=None),
            testexc(f=np.degrees, q_in=(3.0 * u.m), exc=TypeError, msg=None),
            testexc(
                f=np.sin,
                q_in=(3.0 * u.m,),
                exc=TypeError,
                msg="Can only apply 'sin' function to quantities with angle units",
            ),
            testexc(
                f=np.arcsin,
                q_in=(3.0 * u.m,),
                exc=TypeError,
                msg="Can only apply 'arcsin' function to dimensionless quantities",
            ),
            testexc(
                f=np.cos,
                q_in=(3.0 * u.s,),
                exc=TypeError,
                msg="Can only apply 'cos' function to quantities with angle units",
            ),
            testexc(
                f=np.arccos,
                q_in=(3.0 * u.s,),
                exc=TypeError,
                msg="Can only apply 'arccos' function to dimensionless quantities",
            ),
            testexc(
                f=np.tan,
                q_in=(np.array([1, 2, 3]) * u.N,),
                exc=TypeError,
                msg="Can only apply 'tan' function to quantities with angle units",
            ),
            testexc(
                f=np.arctan,
                q_in=(np.array([1, 2, 3]) * u.N,),
                exc=TypeError,
                msg="Can only apply 'arctan' function to dimensionless quantities",
            ),
            testexc(
                f=np.arctan2,
                q_in=(np.array([1, 2, 3]) * u.N, 1.0 * u.s),
                exc=u.UnitsError,
                msg="compatible dimensions",
            ),
            testexc(
                f=np.arctan2,
                q_in=(np.array([1, 2, 3]) * u.N, 1.0),
                exc=u.UnitsError,
                msg="dimensionless quantities when other arg",
            ),
        ),
    )
    def test_testexcs(self, te):
        return test_testexc(te)

    @pytest.mark.parametrize(
        "tw",
        (testwarn(f=np.arcsin, q_in=(27.0 * u.pc / (15 * u.kpc),), wfilter="error"),),
    )
    def test_testwarns(self, tw):
        return test_testwarn(tw)


class TestQuantityMathFuncs:
    """
    Test other mathematical functions
    """

    def test_multiply_scalar(self):
        assert np.multiply(4.0 * u.m, 2.0 / u.s) == 8.0 * u.m / u.s
        assert np.multiply(4.0 * u.m, 2.0) == 8.0 * u.m
        assert np.multiply(4.0, 2.0 / u.s) == 8.0 / u.s

    def test_multiply_array(self):
        assert np.all(
            np.multiply(np.arange(3.0) * u.m, 2.0 / u.s)
            == np.arange(0, 6.0, 2.0) * u.m / u.s
        )

    @pytest.mark.skipif(
        not isinstance(getattr(np, "matmul", None), np.ufunc),
        reason="np.matmul is not yet a gufunc",
    )
    def test_matmul(self):
        q = np.arange(3.0) * u.m
        r = np.matmul(q, q)
        assert r == 5.0 * u.m**2
        # less trivial case.
        q1 = np.eye(3) * u.m
        q2 = np.array(
            [[[1., 0., 0.],
              [0., 1., 0.],
              [0., 0., 1.]],
             [[0., 1., 0.],
              [0., 0., 1.],
              [1., 0., 0.]],
             [[0., 0., 1.],
              [1., 0., 0.],
              [0., 1., 0.]]]
        ) / u.s  # fmt: skip
        r2 = np.matmul(q1, q2)
        assert np.all(r2 == np.matmul(q1.value, q2.value) * q1.unit * q2.unit)

    @pytest.mark.parametrize("function", (np.divide, np.true_divide))
    def test_divide_scalar(self, function):
        assert function(4.0 * u.m, 2.0 * u.s) == function(4.0, 2.0) * u.m / u.s
        assert function(4.0 * u.m, 2.0) == function(4.0, 2.0) * u.m
        assert function(4.0, 2.0 * u.s) == function(4.0, 2.0) / u.s

    @pytest.mark.parametrize("function", (np.divide, np.true_divide))
    def test_divide_array(self, function):
        assert np.all(
            function(np.arange(3.0) * u.m, 2.0 * u.s)
            == function(np.arange(3.0), 2.0) * u.m / u.s
        )

    def test_floor_divide_remainder_and_divmod(self):
        inch = u.Unit(0.0254 * u.m)
        dividend = np.array([1.0, 2.0, 3.0]) * u.m
        divisor = np.array([3.0, 4.0, 5.0]) * inch
        quotient = dividend // divisor
        remainder = dividend % divisor
        assert_allclose(quotient.value, [13.0, 19.0, 23.0])
        assert quotient.unit == u.dimensionless_unscaled
        assert_allclose(remainder.value, [0.0094, 0.0696, 0.079])
        assert remainder.unit == dividend.unit
        quotient2 = np.floor_divide(dividend, divisor)
        remainder2 = np.remainder(dividend, divisor)
        assert np.all(quotient2 == quotient)
        assert np.all(remainder2 == remainder)
        quotient3, remainder3 = divmod(dividend, divisor)
        assert np.all(quotient3 == quotient)
        assert np.all(remainder3 == remainder)

        with pytest.raises(TypeError):
            divmod(dividend, u.km)

        with pytest.raises(TypeError):
            dividend // u.km

        with pytest.raises(TypeError):
            dividend % u.km

        quotient4, remainder4 = np.divmod(dividend, divisor)
        assert np.all(quotient4 == quotient)
        assert np.all(remainder4 == remainder)
        with pytest.raises(TypeError):
            np.divmod(dividend, u.km)

    def test_sqrt_scalar(self):
        assert np.sqrt(4.0 * u.m) == 2.0 * u.m**0.5

    def test_sqrt_array(self):
        assert np.all(
            np.sqrt(np.array([1.0, 4.0, 9.0]) * u.m)
            == np.array([1.0, 2.0, 3.0]) * u.m**0.5
        )

    def test_square_scalar(self):
        assert np.square(4.0 * u.m) == 16.0 * u.m**2

    def test_square_array(self):
        assert np.all(
            np.square(np.array([1.0, 2.0, 3.0]) * u.m)
            == np.array([1.0, 4.0, 9.0]) * u.m**2
        )

    def test_reciprocal_scalar(self):
        assert np.reciprocal(4.0 * u.m) == 0.25 / u.m

    def test_reciprocal_array(self):
        assert np.all(
            np.reciprocal(np.array([1.0, 2.0, 4.0]) * u.m)
            == np.array([1.0, 0.5, 0.25]) / u.m
        )

    def test_heaviside_scalar(self):
        assert np.heaviside(0.0 * u.m, 0.5) == 0.5 * u.dimensionless_unscaled
        assert (
            np.heaviside(0.0 * u.s, 25 * u.percent) == 0.25 * u.dimensionless_unscaled
        )
        assert np.heaviside(2.0 * u.J, 0.25) == 1.0 * u.dimensionless_unscaled

    def test_heaviside_array(self):
        values = np.array([-1.0, 0.0, 0.0, +1.0])
        halfway = np.array([0.75, 0.25, 0.75, 0.25]) * u.dimensionless_unscaled
        assert np.all(
            np.heaviside(values * u.m, halfway * u.dimensionless_unscaled)
            == [0, 0.25, 0.75, +1.0] * u.dimensionless_unscaled
        )

    @pytest.mark.parametrize("function", (np.cbrt,))
    def test_cbrt_scalar(self, function):
        assert function(8.0 * u.m**3) == 2.0 * u.m

    @pytest.mark.parametrize("function", (np.cbrt,))
    def test_cbrt_array(self, function):
        # Calculate cbrt on both sides since on Windows the cube root of 64
        # does not exactly equal 4.  See 4388.
        values = np.array([1.0, 8.0, 64.0])
        assert np.all(function(values * u.m**3) == function(values) * u.m)

    def test_power_scalar(self):
        assert np.power(4.0 * u.m, 2.0) == 16.0 * u.m**2
        assert np.power(4.0, 200.0 * u.cm / u.m) == u.Quantity(
            16.0, u.dimensionless_unscaled
        )
        # regression check on #1696
        assert np.power(4.0 * u.m, 0.0) == 1.0 * u.dimensionless_unscaled

    def test_power_array(self):
        assert np.all(
            np.power(np.array([1.0, 2.0, 3.0]) * u.m, 3.0)
            == np.array([1.0, 8.0, 27.0]) * u.m**3
        )
        # regression check on #1696
        assert np.all(
            np.power(np.arange(4.0) * u.m, 0.0) == 1.0 * u.dimensionless_unscaled
        )

    def test_float_power_array(self):
        assert np.all(
            np.float_power(np.array([1.0, 2.0, 3.0]) * u.m, 3.0)
            == np.array([1.0, 8.0, 27.0]) * u.m**3
        )
        # regression check on #1696
        assert np.all(
            np.float_power(np.arange(4.0) * u.m, 0.0) == 1.0 * u.dimensionless_unscaled
        )

    def test_power_array_array(self):
        with pytest.raises(ValueError):
            np.power(4.0 * u.m, [2.0, 4.0])

    def test_power_array_array2(self):
        with pytest.raises(ValueError):
            np.power([2.0, 4.0] * u.m, [2.0, 4.0])

    def test_power_array_array3(self):
        # Identical unit fractions are converted automatically to dimensionless
        # and should be allowed as base for np.power: #4764
        q = [2.0, 4.0] * u.m / u.m
        powers = [2.0, 4.0]
        res = np.power(q, powers)
        assert np.all(res.value == q.value**powers)
        assert res.unit == u.dimensionless_unscaled
        # The same holds for unit fractions that are scaled dimensionless.
        q2 = [2.0, 4.0] * u.m / u.cm
        # Test also against different types of exponent
        for cls in (list, tuple, np.array, np.ma.array, u.Quantity):
            res2 = np.power(q2, cls(powers))
            assert np.all(res2.value == q2.to_value(1) ** powers)
            assert res2.unit == u.dimensionless_unscaled
        # Though for single powers, we keep the composite unit.
        res3 = q2**2
        assert np.all(res3.value == q2.value**2)
        assert res3.unit == q2.unit**2
        assert np.all(res3 == q2 ** [2, 2])

    def test_power_invalid(self):
        with pytest.raises(TypeError, match="raise something to a dimensionless"):
            np.power(3.0, 4.0 * u.m)

    def test_copysign_scalar(self):
        assert np.copysign(3 * u.m, 1.0) == 3.0 * u.m
        assert np.copysign(3 * u.m, 1.0 * u.s) == 3.0 * u.m
        assert np.copysign(3 * u.m, -1.0) == -3.0 * u.m
        assert np.copysign(3 * u.m, -1.0 * u.s) == -3.0 * u.m

    def test_copysign_array(self):
        assert np.all(
            np.copysign(np.array([1.0, 2.0, 3.0]) * u.s, -1.0)
            == -np.array([1.0, 2.0, 3.0]) * u.s
        )
        assert np.all(
            np.copysign(np.array([1.0, 2.0, 3.0]) * u.s, -1.0 * u.m)
            == -np.array([1.0, 2.0, 3.0]) * u.s
        )
        assert np.all(
            np.copysign(
                np.array([1.0, 2.0, 3.0]) * u.s, np.array([-2.0, 2.0, -4.0]) * u.m
            )
            == np.array([-1.0, 2.0, -3.0]) * u.s
        )

        q = np.copysign(np.array([1.0, 2.0, 3.0]), -3 * u.m)
        assert np.all(q == np.array([-1.0, -2.0, -3.0]))
        assert not isinstance(q, u.Quantity)

    def test_ldexp_scalar(self):
        assert np.ldexp(4.0 * u.m, 2) == 16.0 * u.m

    def test_ldexp_array(self):
        assert np.all(
            np.ldexp(np.array([1.0, 2.0, 3.0]) * u.m, [3, 2, 1])
            == np.array([8.0, 8.0, 6.0]) * u.m
        )

    def test_ldexp_invalid(self):
        with pytest.raises(TypeError):
            np.ldexp(3.0 * u.m, 4.0)

        with pytest.raises(TypeError):
            np.ldexp(3.0, u.Quantity(4, u.m, dtype=int))

    @pytest.mark.parametrize(
        "function", (np.exp, np.expm1, np.exp2, np.log, np.log2, np.log10, np.log1p)
    )
    def test_exp_scalar(self, function):
        q = function(3.0 * u.m / (6.0 * u.m))
        assert q.unit == u.dimensionless_unscaled
        assert q.value == function(0.5)

    @pytest.mark.parametrize(
        "function", (np.exp, np.expm1, np.exp2, np.log, np.log2, np.log10, np.log1p)
    )
    def test_exp_array(self, function):
        q = function(np.array([2.0, 3.0, 6.0]) * u.m / (6.0 * u.m))
        assert q.unit == u.dimensionless_unscaled
        assert np.all(q.value == function(np.array([1.0 / 3.0, 1.0 / 2.0, 1.0])))
        # should also work on quantities that can be made dimensionless
        q2 = function(np.array([2.0, 3.0, 6.0]) * u.m / (6.0 * u.cm))
        assert q2.unit == u.dimensionless_unscaled
        assert_allclose(q2.value, function(np.array([100.0 / 3.0, 100.0 / 2.0, 100.0])))

    @pytest.mark.parametrize(
        "function", (np.exp, np.expm1, np.exp2, np.log, np.log2, np.log10, np.log1p)
    )
    def test_exp_invalid_units(self, function):
        # Can't use exp() with non-dimensionless quantities
        with pytest.raises(
            TypeError,
            match=(
                f"Can only apply '{function.__name__}' function "
                "to dimensionless quantities"
            ),
        ):
            function(3.0 * u.m / u.s)

    def test_modf_scalar(self):
        q = np.modf(9.0 * u.m / (600.0 * u.cm))
        assert q == (0.5 * u.dimensionless_unscaled, 1.0 * u.dimensionless_unscaled)

    def test_modf_array(self):
        v = np.arange(10.0) * u.m / (500.0 * u.cm)
        q = np.modf(v)
        n = np.modf(v.to_value(u.dimensionless_unscaled))
        assert q[0].unit == u.dimensionless_unscaled
        assert q[1].unit == u.dimensionless_unscaled
        assert all(q[0].value == n[0])
        assert all(q[1].value == n[1])

    def test_frexp_scalar(self):
        q = np.frexp(3.0 * u.m / (6.0 * u.m))
        assert q == (np.array(0.5), np.array(0.0))

    def test_frexp_array(self):
        q = np.frexp(np.array([2.0, 3.0, 6.0]) * u.m / (6.0 * u.m))
        assert all(
            (_q0, _q1) == np.frexp(_d)
            for _q0, _q1, _d in zip(q[0], q[1], [1.0 / 3.0, 1.0 / 2.0, 1.0])
        )

    def test_frexp_invalid_units(self):
        # Can't use prod() with non-dimensionless quantities
        with pytest.raises(
            TypeError,
            match=(
                "Can only apply 'frexp' function to unscaled dimensionless quantities"
            ),
        ):
            np.frexp(3.0 * u.m / u.s)

        # also does not work on quantities that can be made dimensionless
        with pytest.raises(
            TypeError,
            match=(
                "Can only apply 'frexp' function to unscaled dimensionless quantities"
            ),
        ):
            np.frexp(np.array([2.0, 3.0, 6.0]) * u.m / (6.0 * u.cm))

    @pytest.mark.parametrize("function", (np.logaddexp, np.logaddexp2))
    def test_dimensionless_twoarg_array(self, function):
        q = function(np.array([2.0, 3.0, 6.0]) * u.m / (6.0 * u.cm), 1.0)
        assert q.unit == u.dimensionless_unscaled
        assert_allclose(
            q.value, function(np.array([100.0 / 3.0, 100.0 / 2.0, 100.0]), 1.0)
        )

    @pytest.mark.parametrize("function", (np.logaddexp, np.logaddexp2))
    def test_dimensionless_twoarg_invalid_units(self, function):
        with pytest.raises(
            TypeError,
            match=(
                f"Can only apply '{function.__name__}' function to dimensionless"
                " quantities"
            ),
        ):
            function(1.0 * u.km / u.s, 3.0 * u.m / u.s)


class TestInvariantUfuncs:
    @pytest.mark.parametrize(
        "ufunc",
        [
            np.absolute,
            np.fabs,
            np.conj,
            np.conjugate,
            np.negative,
            np.spacing,
            np.rint,
            np.floor,
            np.ceil,
            np.positive,
        ],
    )
    def test_invariant_scalar(self, ufunc):
        q_i = 4.7 * u.m
        q_o = ufunc(q_i)
        assert isinstance(q_o, u.Quantity)
        assert q_o.unit == q_i.unit
        assert q_o.value == ufunc(q_i.value)

    @pytest.mark.parametrize(
        "ufunc", [np.absolute, np.conjugate, np.negative, np.rint, np.floor, np.ceil]
    )
    def test_invariant_array(self, ufunc):
        q_i = np.array([-3.3, 2.1, 10.2]) * u.kg / u.s
        q_o = ufunc(q_i)
        assert isinstance(q_o, u.Quantity)
        assert q_o.unit == q_i.unit
        assert np.all(q_o.value == ufunc(q_i.value))

    @pytest.mark.parametrize(
        "ufunc",
        [
            np.add,
            np.subtract,
            np.hypot,
            np.maximum,
            np.minimum,
            np.nextafter,
            np.remainder,
            np.mod,
            np.fmod,
        ],
    )
    def test_invariant_twoarg_scalar(self, ufunc):
        q_i1 = 4.7 * u.m
        q_i2 = 9.4 * u.km
        q_o = ufunc(q_i1, q_i2)
        assert isinstance(q_o, u.Quantity)
        assert q_o.unit == q_i1.unit
        assert_allclose(q_o.value, ufunc(q_i1.value, q_i2.to_value(q_i1.unit)))

    @pytest.mark.parametrize(
        "ufunc",
        [
            np.add,
            np.subtract,
            np.hypot,
            np.maximum,
            np.minimum,
            np.nextafter,
            np.remainder,
            np.mod,
            np.fmod,
        ],
    )
    def test_invariant_twoarg_array(self, ufunc):
        q_i1 = np.array([-3.3, 2.1, 10.2]) * u.kg / u.s
        q_i2 = np.array([10.0, -5.0, 1.0e6]) * u.g / u.us
        q_o = ufunc(q_i1, q_i2)
        assert isinstance(q_o, u.Quantity)
        assert q_o.unit == q_i1.unit
        assert_allclose(q_o.value, ufunc(q_i1.value, q_i2.to_value(q_i1.unit)))

    @pytest.mark.parametrize(
        ("ufunc", "arbitrary"),
        [
            (np.add, 0.0),
            (np.subtract, 0.0),
            (np.hypot, 0.0),
            (np.maximum, 0.0),
            (np.minimum, 0.0),
            (np.nextafter, 0.0),
            (np.remainder, np.inf),
            (np.mod, np.inf),
            (np.fmod, np.inf),
        ],
    )
    def test_invariant_twoarg_one_arbitrary(self, ufunc, arbitrary):
        q_i1 = np.array([-3.3, 2.1, 10.2]) * u.kg / u.s
        q_o = ufunc(q_i1, arbitrary)
        assert isinstance(q_o, u.Quantity)
        assert q_o.unit == q_i1.unit
        assert_allclose(q_o.value, ufunc(q_i1.value, arbitrary))

    @pytest.mark.parametrize(
        "ufunc",
        [
            np.add,
            np.subtract,
            np.hypot,
            np.maximum,
            np.minimum,
            np.nextafter,
            np.remainder,
            np.mod,
            np.fmod,
        ],
    )
    def test_invariant_twoarg_invalid_units(self, ufunc):
        q_i1 = 4.7 * u.m
        q_i2 = 9.4 * u.s
        with pytest.raises(u.UnitsError, match="compatible dimensions"):
            ufunc(q_i1, q_i2)


class TestComparisonUfuncs:
    @pytest.mark.parametrize(
        "ufunc",
        [np.greater, np.greater_equal, np.less, np.less_equal, np.not_equal, np.equal],
    )
    def test_comparison_valid_units(self, ufunc):
        q_i1 = np.array([-3.3, 2.1, 10.2]) * u.kg / u.s
        q_i2 = np.array([10.0, -5.0, 1.0e6]) * u.g / u.Ms
        q_o = ufunc(q_i1, q_i2)
        assert not isinstance(q_o, u.Quantity)
        assert q_o.dtype == bool
        assert np.all(q_o == ufunc(q_i1.value, q_i2.to_value(q_i1.unit)))
        q_o2 = ufunc(q_i1 / q_i2, 2.0)
        assert not isinstance(q_o2, u.Quantity)
        assert q_o2.dtype == bool
        assert np.all(
            q_o2 == ufunc((q_i1 / q_i2).to_value(u.dimensionless_unscaled), 2.0)
        )
        # comparison with 0., inf, nan is OK even for dimensional quantities
        # (though ignore numpy runtime warnings for comparisons with nan).
        with warnings.catch_warnings():
            warnings.filterwarnings("ignore", category=RuntimeWarning)
            for arbitrary_unit_value in (0.0, np.inf, np.nan):
                ufunc(q_i1, arbitrary_unit_value)
                ufunc(q_i1, arbitrary_unit_value * np.ones(len(q_i1)))
            # and just for completeness
            ufunc(q_i1, np.array([0.0, np.inf, np.nan]))

    @pytest.mark.parametrize(
        "ufunc",
        [np.greater, np.greater_equal, np.less, np.less_equal, np.not_equal, np.equal],
    )
    def test_comparison_invalid_units(self, ufunc):
        q_i1 = 4.7 * u.m
        q_i2 = 9.4 * u.s
        with pytest.raises(u.UnitsError, match="compatible dimensions"):
            ufunc(q_i1, q_i2)

    @pytest.mark.parametrize("ufunc", (np.isfinite, np.isinf, np.isnan, np.signbit))
    def test_onearg_test_ufuncs(self, ufunc):
        q = [1.0, np.inf, -np.inf, np.nan, -1.0, 0.0] * u.m
        out = ufunc(q)
        assert not isinstance(out, u.Quantity)
        assert out.dtype == bool
        assert np.all(out == ufunc(q.value))

    # Ignore RuntimeWarning raised on Windows and s390.
    @pytest.mark.filterwarnings("ignore:.*invalid value encountered in sign")
    def test_sign(self):
        q = [1.0, np.inf, -np.inf, np.nan, -1.0, 0.0] * u.m

        out = np.sign(q)
        assert not isinstance(out, u.Quantity)
        assert out.dtype == q.dtype
        assert np.all((out == np.sign(q.value)) | (np.isnan(out) & np.isnan(q.value)))


class TestInplaceUfuncs:
    @pytest.mark.parametrize("value", [1.0, np.arange(10.0)])
    def test_one_argument_ufunc_inplace(self, value):
        # without scaling
        s = value * u.rad
        check = s
        np.sin(s, out=s)
        assert check is s
        assert check.unit == u.dimensionless_unscaled
        # with scaling
        s2 = (value * u.rad).to(u.deg)
        check2 = s2
        np.sin(s2, out=s2)
        assert check2 is s2
        assert check2.unit == u.dimensionless_unscaled
        assert_allclose(s.value, s2.value)

    @pytest.mark.parametrize("value", [1.0, np.arange(10.0)])
    def test_one_argument_ufunc_inplace_2(self, value):
        """Check inplace works with non-quantity input and quantity output"""
        s = value * u.m
        check = s
        np.absolute(value, out=s)
        assert check is s
        assert np.all(check.value == np.absolute(value))
        assert check.unit is u.dimensionless_unscaled
        np.sqrt(value, out=s)
        assert check is s
        assert np.all(check.value == np.sqrt(value))
        assert check.unit is u.dimensionless_unscaled
        np.exp(value, out=s)
        assert check is s
        assert np.all(check.value == np.exp(value))
        assert check.unit is u.dimensionless_unscaled
        np.arcsin(value / 10.0, out=s)
        assert check is s
        assert np.all(check.value == np.arcsin(value / 10.0))
        assert check.unit is u.radian

    @pytest.mark.parametrize("value", [1.0, np.arange(10.0)])
    def test_one_argument_two_output_ufunc_inplace(self, value):
        v = 100.0 * value * u.cm / u.m
        v_copy = v.copy()
        tmp = v.copy()
        check = v
        np.modf(v, tmp, v)
        assert check is v
        assert check.unit == u.dimensionless_unscaled
        v2 = v_copy.to(u.dimensionless_unscaled)
        check2 = v2
        np.modf(v2, tmp, v2)
        assert check2 is v2
        assert check2.unit == u.dimensionless_unscaled
        # can also replace in last position if no scaling is needed
        v3 = v_copy.to(u.dimensionless_unscaled)
        check3 = v3
        np.modf(v3, v3, tmp)
        assert check3 is v3
        assert check3.unit == u.dimensionless_unscaled
        # can also replace input with first output when scaling
        v4 = v_copy.copy()
        check4 = v4
        np.modf(v4, v4, tmp)
        assert check4 is v4
        assert check4.unit == u.dimensionless_unscaled

    @pytest.mark.parametrize("value", [1.0, np.arange(10.0)])
    def test_two_argument_ufunc_inplace_1(self, value):
        s = value * u.cycle
        check = s
        s /= 2.0
        assert check is s
        assert np.all(check.value == value / 2.0)
        s /= u.s
        assert check is s
        assert check.unit == u.cycle / u.s
        s *= 2.0 * u.s
        assert check is s
        assert np.all(check == value * u.cycle)

    @pytest.mark.parametrize("value", [1.0, np.arange(10.0)])
    def test_two_argument_ufunc_inplace_2(self, value):
        s = value * u.cycle
        check = s
        np.arctan2(s, s, out=s)
        assert check is s
        assert check.unit == u.radian
        with pytest.raises(u.UnitsError):
            s += 1.0 * u.m
        assert check is s
        assert check.unit == u.radian
        np.arctan2(1.0 * u.deg, s, out=s)
        assert check is s
        assert check.unit == u.radian
        np.add(1.0 * u.deg, s, out=s)
        assert check is s
        assert check.unit == u.deg
        np.multiply(2.0 / u.s, s, out=s)
        assert check is s
        assert check.unit == u.deg / u.s

    def test_two_argument_ufunc_inplace_3(self):
        s = np.array([1.0, 2.0, 3.0]) * u.dimensionless_unscaled
        np.add(np.array([1.0, 2.0, 3.0]), np.array([1.0, 2.0, 3.0]) * 2.0, out=s)
        assert np.all(s.value == np.array([3.0, 6.0, 9.0]))
        assert s.unit is u.dimensionless_unscaled
        np.arctan2(np.array([1.0, 2.0, 3.0]), np.array([1.0, 2.0, 3.0]) * 2.0, out=s)
        assert_allclose(s.value, np.arctan2(1.0, 2.0))
        assert s.unit is u.radian

    @pytest.mark.parametrize("value", [1.0, np.arange(10.0)])
    def test_two_argument_two_output_ufunc_inplace(self, value):
        v = value * u.m
        divisor = 70.0 * u.cm
        v1 = v.copy()
        tmp = v.copy()
        check = np.divmod(v1, divisor, out=(tmp, v1))
        assert check[0] is tmp and check[1] is v1
        assert tmp.unit == u.dimensionless_unscaled
        assert v1.unit == v.unit
        v2 = v.copy()
        check2 = np.divmod(v2, divisor, out=(v2, tmp))
        assert check2[0] is v2 and check2[1] is tmp
        assert v2.unit == u.dimensionless_unscaled
        assert tmp.unit == v.unit
        v3a = v.copy()
        v3b = v.copy()
        check3 = np.divmod(v3a, divisor, out=(v3a, v3b))
        assert check3[0] is v3a and check3[1] is v3b
        assert v3a.unit == u.dimensionless_unscaled
        assert v3b.unit == v.unit

    def test_ufunc_inplace_non_contiguous_data(self):
        # ensure inplace works also for non-contiguous data (closes #1834)
        s = np.arange(10.0) * u.m
        s_copy = s.copy()
        s2 = s[::2]
        s2 += 1.0 * u.cm
        assert np.all(s[::2] > s_copy[::2])
        assert np.all(s[1::2] == s_copy[1::2])

    def test_ufunc_inplace_non_standard_dtype(self):
        """Check that inplace operations check properly for casting.

        First two tests that check that float32 is kept close #3976.
        """
        a1 = u.Quantity([1, 2, 3, 4], u.m, dtype=np.float32)
        a1 *= np.float32(10)
        assert a1.unit is u.m
        assert a1.dtype == np.float32
        a2 = u.Quantity([1, 2, 3, 4], u.m, dtype=np.float32)
        a2 += 20.0 * u.km
        assert a2.unit is u.m
        assert a2.dtype == np.float32
        # For integer, in-place only works if no conversion is done.
        a3 = u.Quantity([1, 2, 3, 4], u.m, dtype=np.int32)
        a3 += u.Quantity(10, u.m, dtype=np.int64)
        assert a3.unit is u.m
        assert a3.dtype == np.int32
        a4 = u.Quantity([1, 2, 3, 4], u.m, dtype=np.int32)
        with pytest.raises(TypeError):
            a4 += u.Quantity(10, u.mm, dtype=np.int64)

    @pytest.mark.parametrize("ufunc", (np.equal, np.greater))
    def test_comparison_ufuncs_inplace(self, ufunc):
        q_i1 = np.array([-3.3, 2.1, 10.2]) * u.kg / u.s
        q_i2 = np.array([10.0, -5.0, 1.0e6]) * u.g / u.Ms
        check = np.empty(q_i1.shape, bool)
        ufunc(q_i1.value, q_i2.to_value(q_i1.unit), out=check)

        result = np.empty(q_i1.shape, bool)
        q_o = ufunc(q_i1, q_i2, out=result)
        assert q_o is result
        assert type(q_o) is np.ndarray
        assert q_o.dtype == bool
        assert np.all(q_o == check)

    @pytest.mark.parametrize("ufunc", (np.isfinite, np.signbit))
    def test_onearg_test_ufuncs_inplace(self, ufunc):
        q = [1.0, np.inf, -np.inf, np.nan, -1.0, 0.0] * u.m
        check = np.empty(q.shape, bool)
        ufunc(q.value, out=check)

        result = np.empty(q.shape, bool)
        out = ufunc(q, out=result)
        assert out is result
        assert type(out) is np.ndarray
        assert out.dtype == bool
        assert np.all(out == ufunc(q.value))

    # Ignore RuntimeWarning raised on Windows and s390.
    @pytest.mark.filterwarnings("ignore:.*invalid value encountered in sign")
    def test_sign_inplace(self):
        q = [1.0, np.inf, -np.inf, np.nan, -1.0, 0.0] * u.m
        check = np.empty(q.shape, q.dtype)

        np.sign(q.value, out=check)

        result = np.empty(q.shape, q.dtype)
        out = np.sign(q, out=result)
        assert out is result
        assert type(out) is np.ndarray
        assert out.dtype == q.dtype
        assert np.all((out == np.sign(q.value)) | (np.isnan(out) & np.isnan(q.value)))

    def test_ndarray_inplace_op_with_quantity(self):
        """Regression test for gh-13911."""
        a = np.arange(3.0)
        q = u.Quantity([12.5, 25.0], u.percent)
        a[:2] += q  # This used to fail
        assert_array_equal(a, np.array([0.125, 1.25, 2.0]))


@pytest.mark.skipif(
    not hasattr(np.core.umath, "clip"), reason="no clip ufunc available"
)
class TestClip:
    """Test the clip ufunc.

    In numpy, this is hidden behind a function that does not backwards
    compatibility checks.  We explicitly test the ufunc here.
    """

    def setup_method(self):
        self.clip = np.core.umath.clip

    def test_clip_simple(self):
        q = np.arange(-1.0, 10.0) * u.m
        q_min = 125 * u.cm
        q_max = 0.0055 * u.km
        result = self.clip(q, q_min, q_max)
        assert result.unit == q.unit
        expected = (
            self.clip(q.value, q_min.to_value(q.unit), q_max.to_value(q.unit)) * q.unit
        )
        assert np.all(result == expected)

    def test_clip_unitless_parts(self):
        q = np.arange(-1.0, 10.0) * u.m
        qlim = 0.0055 * u.km
        # one-sided
        result1 = self.clip(q, -np.inf, qlim)
        expected1 = self.clip(q.value, -np.inf, qlim.to_value(q.unit)) * q.unit
        assert np.all(result1 == expected1)
        result2 = self.clip(q, qlim, np.inf)
        expected2 = self.clip(q.value, qlim.to_value(q.unit), np.inf) * q.unit
        assert np.all(result2 == expected2)
        # Zero
        result3 = self.clip(q, np.zeros(q.shape), qlim)
        expected3 = self.clip(q.value, 0, qlim.to_value(q.unit)) * q.unit
        assert np.all(result3 == expected3)
        # Two unitless parts, array-shaped.
        result4 = self.clip(q, np.zeros(q.shape), np.full(q.shape, np.inf))
        expected4 = self.clip(q.value, 0, np.inf) * q.unit
        assert np.all(result4 == expected4)

    def test_clip_dimensionless(self):
        q = np.arange(-1.0, 10.0) * u.dimensionless_unscaled
        result = self.clip(q, 200 * u.percent, 5.0)
        expected = self.clip(q, 2.0, 5.0)
        assert result.unit == u.dimensionless_unscaled
        assert np.all(result == expected)

    def test_clip_ndarray(self):
        a = np.arange(-1.0, 10.0)
        result = self.clip(a, 200 * u.percent, 5.0 * u.dimensionless_unscaled)
        assert isinstance(result, u.Quantity)
        expected = self.clip(a, 2.0, 5.0) * u.dimensionless_unscaled
        assert np.all(result == expected)

    def test_clip_quantity_inplace(self):
        q = np.arange(-1.0, 10.0) * u.m
        q_min = 125 * u.cm
        q_max = 0.0055 * u.km
        expected = (
            self.clip(q.value, q_min.to_value(q.unit), q_max.to_value(q.unit)) * q.unit
        )
        result = self.clip(q, q_min, q_max, out=q)
        assert result is q
        assert np.all(result == expected)

    def test_clip_ndarray_dimensionless_output(self):
        a = np.arange(-1.0, 10.0)
        q = np.zeros_like(a) * u.m
        expected = self.clip(a, 2.0, 5.0) * u.dimensionless_unscaled
        result = self.clip(a, 200 * u.percent, 5.0 * u.dimensionless_unscaled, out=q)
        assert result is q
        assert result.unit == u.dimensionless_unscaled
        assert np.all(result == expected)

    def test_clip_errors(self):
        q = np.arange(-1.0, 10.0) * u.m
        with pytest.raises(u.UnitsError):
            self.clip(q, 0, 1 * u.s)
        with pytest.raises(u.UnitsError):
            self.clip(q.value, 0, 1 * u.s)
        with pytest.raises(u.UnitsError):
            self.clip(q, -1, 0.0)
        with pytest.raises(u.UnitsError):
            self.clip(q, 0.0, 1.0)


class TestUfuncAt:
    """Test that 'at' method for ufuncs (calculates in-place at given indices)

    For Quantities, since calculations are in-place, it makes sense only
    if the result is still a quantity, and if the unit does not have to change
    """

    def test_one_argument_ufunc_at(self):
        q = np.arange(10.0) * u.m
        i = np.array([1, 2])
        qv = q.value.copy()
        np.negative.at(q, i)
        np.negative.at(qv, i)
        assert np.all(q.value == qv)
        assert q.unit is u.m

        # cannot change from quantity to bool array
        with pytest.raises(TypeError):
            np.isfinite.at(q, i)

        # for selective in-place, cannot change the unit
        with pytest.raises(u.UnitsError):
            np.square.at(q, i)

        # except if the unit does not change (i.e., dimensionless)
        d = np.arange(10.0) * u.dimensionless_unscaled
        dv = d.value.copy()
        np.square.at(d, i)
        np.square.at(dv, i)
        assert np.all(d.value == dv)
        assert d.unit is u.dimensionless_unscaled

        d = np.arange(10.0) * u.dimensionless_unscaled
        dv = d.value.copy()
        np.log.at(d, i)
        np.log.at(dv, i)
        assert np.all(d.value == dv)
        assert d.unit is u.dimensionless_unscaled

        # also for sine it doesn't work, even if given an angle
        a = np.arange(10.0) * u.radian
        with pytest.raises(u.UnitsError):
            np.sin.at(a, i)

        # except, for consistency, if we have made radian equivalent to
        # dimensionless (though hopefully it will never be needed)
        av = a.value.copy()
        with u.add_enabled_equivalencies(u.dimensionless_angles()):
            np.sin.at(a, i)
            np.sin.at(av, i)
            assert_allclose(a.value, av)

            # but we won't do double conversion
            ad = np.arange(10.0) * u.degree
            with pytest.raises(u.UnitsError):
                np.sin.at(ad, i)

    def test_two_argument_ufunc_at(self):
        s = np.arange(10.0) * u.m
        i = np.array([1, 2])
        check = s.value.copy()
        np.add.at(s, i, 1.0 * u.km)
        np.add.at(check, i, 1000.0)
        assert np.all(s.value == check)
        assert s.unit is u.m

        with pytest.raises(u.UnitsError):
            np.add.at(s, i, 1.0 * u.s)

        # also raise UnitsError if unit would have to be changed
        with pytest.raises(u.UnitsError):
            np.multiply.at(s, i, 1 * u.s)

        # but be fine if it does not
        s = np.arange(10.0) * u.m
        check = s.value.copy()
        np.multiply.at(s, i, 2.0 * u.dimensionless_unscaled)
        np.multiply.at(check, i, 2)
        assert np.all(s.value == check)
        s = np.arange(10.0) * u.m
        np.multiply.at(s, i, 2.0)
        assert np.all(s.value == check)

        # of course cannot change class of data either
        with pytest.raises(TypeError):
            np.greater.at(s, i, 1.0 * u.km)


class TestUfuncReduceReduceatAccumulate:
    """Test 'reduce', 'reduceat' and 'accumulate' methods for ufuncs

    For Quantities, it makes sense only if the unit does not have to change
    """

    def test_one_argument_ufunc_reduce_accumulate(self):
        # one argument cannot be used
        s = np.arange(10.0) * u.radian
        i = np.array([0, 5, 1, 6])
        with pytest.raises(ValueError):
            np.sin.reduce(s)
        with pytest.raises(ValueError):
            np.sin.accumulate(s)
        with pytest.raises(ValueError):
            np.sin.reduceat(s, i)

    def test_two_argument_ufunc_reduce_accumulate(self):
        s = np.arange(10.0) * u.m
        i = np.array([0, 5, 1, 6])
        check = s.value.copy()
        s_add_reduce = np.add.reduce(s)
        check_add_reduce = np.add.reduce(check)
        assert s_add_reduce.value == check_add_reduce
        assert s_add_reduce.unit is u.m

        s_add_accumulate = np.add.accumulate(s)
        check_add_accumulate = np.add.accumulate(check)
        assert np.all(s_add_accumulate.value == check_add_accumulate)
        assert s_add_accumulate.unit is u.m

        s_add_reduceat = np.add.reduceat(s, i)
        check_add_reduceat = np.add.reduceat(check, i)
        assert np.all(s_add_reduceat.value == check_add_reduceat)
        assert s_add_reduceat.unit is u.m

        # reduce(at) or accumulate on comparisons makes no sense,
        # as intermediate result is not even a Quantity
        with pytest.raises(TypeError):
            np.greater.reduce(s)

        with pytest.raises(TypeError):
            np.greater.accumulate(s)

        with pytest.raises(TypeError):
            np.greater.reduceat(s, i)

        # raise UnitsError if unit would have to be changed
        with pytest.raises(u.UnitsError):
            np.multiply.reduce(s)

        with pytest.raises(u.UnitsError):
            np.multiply.accumulate(s)

        with pytest.raises(u.UnitsError):
            np.multiply.reduceat(s, i)

        # but be fine if it does not
        s = np.arange(10.0) * u.dimensionless_unscaled
        check = s.value.copy()
        s_multiply_reduce = np.multiply.reduce(s)
        check_multiply_reduce = np.multiply.reduce(check)
        assert s_multiply_reduce.value == check_multiply_reduce
        assert s_multiply_reduce.unit is u.dimensionless_unscaled
        s_multiply_accumulate = np.multiply.accumulate(s)
        check_multiply_accumulate = np.multiply.accumulate(check)
        assert np.all(s_multiply_accumulate.value == check_multiply_accumulate)
        assert s_multiply_accumulate.unit is u.dimensionless_unscaled
        s_multiply_reduceat = np.multiply.reduceat(s, i)
        check_multiply_reduceat = np.multiply.reduceat(check, i)
        assert np.all(s_multiply_reduceat.value == check_multiply_reduceat)
        assert s_multiply_reduceat.unit is u.dimensionless_unscaled


class TestUfuncOuter:
    """Test 'outer' methods for ufuncs

    Just a few spot checks, since it uses the same code as the regular
    ufunc call
    """

    def test_one_argument_ufunc_outer(self):
        # one argument cannot be used
        s = np.arange(10.0) * u.radian
        with pytest.raises(ValueError):
            np.sin.outer(s)

    def test_two_argument_ufunc_outer(self):
        s1 = np.arange(10.0) * u.m
        s2 = np.arange(2.0) * u.s
        check1 = s1.value
        check2 = s2.value
        s12_multiply_outer = np.multiply.outer(s1, s2)
        check12_multiply_outer = np.multiply.outer(check1, check2)
        assert np.all(s12_multiply_outer.value == check12_multiply_outer)
        assert s12_multiply_outer.unit == s1.unit * s2.unit

        # raise UnitsError if appropriate
        with pytest.raises(u.UnitsError):
            np.add.outer(s1, s2)

        # but be fine if it does not
        s3 = np.arange(2.0) * s1.unit
        check3 = s3.value
        s13_add_outer = np.add.outer(s1, s3)
        check13_add_outer = np.add.outer(check1, check3)
        assert np.all(s13_add_outer.value == check13_add_outer)
        assert s13_add_outer.unit is s1.unit

        s13_greater_outer = np.greater.outer(s1, s3)
        check13_greater_outer = np.greater.outer(check1, check3)
        assert type(s13_greater_outer) is np.ndarray
        assert np.all(s13_greater_outer == check13_greater_outer)


@dataclasses.dataclass
class DuckQuantity1:
    data: u.Quantity


@dataclasses.dataclass
class DuckQuantity2(DuckQuantity1):
    @property
    def unit(self) -> u.UnitBase:
        return self.data.unit


@dataclasses.dataclass(eq=False)
class DuckQuantity3(DuckQuantity2):
    def __array_ufunc__(self, function, method, *inputs, **kwargs):

        inputs = [inp.data if isinstance(inp, type(self)) else inp for inp in inputs]

        out = kwargs.get("out", None)

        kwargs_copy = {}
        for k in kwargs:
            kwarg = kwargs[k]
            if isinstance(kwarg, type(self)):
                kwargs_copy[k] = kwarg.data
            elif isinstance(kwarg, (list, tuple)):
                kwargs_copy[k] = type(kwarg)(
                    item.data if isinstance(item, type(self)) else item
                    for item in kwarg
                )
            else:
                kwargs_copy[k] = kwarg
        kwargs = kwargs_copy

        for inp in inputs:
            if isinstance(inp, np.ndarray):
                result = inp.__array_ufunc__(function, method, *inputs, **kwargs)
                if result is not NotImplemented:
                    if out is None:
                        return type(self)(result)
                    else:
                        if function.nout == 1:
                            return out[0]
                        else:
                            return out

        return NotImplemented


class TestUfuncReturnsNotImplemented:
    @pytest.mark.parametrize("ufunc", (np.negative, np.abs))
    class TestUnaryUfuncs:
        @pytest.mark.parametrize(
            "duck_quantity",
            [DuckQuantity1(1 * u.mm), DuckQuantity2(1 * u.mm)],
        )
        def test_basic(self, ufunc, duck_quantity):
            with pytest.raises(TypeError, match="bad operand type for .*"):
                ufunc(duck_quantity)

        @pytest.mark.parametrize(
            "duck_quantity", [DuckQuantity3(1 * u.mm), DuckQuantity3([1, 2] * u.mm)]
        )
        @pytest.mark.parametrize("out", [None, "empty"])
        def test_full(self, ufunc, duck_quantity, out):
            out_expected = out
            if out == "empty":
                out = type(duck_quantity)(np.empty_like(ufunc(duck_quantity.data)))
                out_expected = np.empty_like(ufunc(duck_quantity.data))

            result = ufunc(duck_quantity, out=out)
            if out is not None:
                assert result is out

            result_expected = ufunc(duck_quantity.data, out=out_expected)
            assert np.all(result.data == result_expected)

    @pytest.mark.parametrize("ufunc", (np.add, np.multiply, np.less))
    @pytest.mark.parametrize("quantity", (1 * u.m, [1, 2] * u.m))
    class TestBinaryUfuncs:
        @pytest.mark.parametrize(
            "duck_quantity",
            [DuckQuantity1(1 * u.mm), DuckQuantity2(1 * u.mm)],
        )
        def test_basic(self, ufunc, quantity, duck_quantity):
            with pytest.raises(
                (TypeError, ValueError),
                match=(
                    r"(Unsupported operand type\(s\) for ufunc .*)|"
                    r"(unsupported operand type\(s\) for .*)|"
                    r"(Value not scalar compatible or convertible to an int, float, or complex array)"
                ),
            ):
                ufunc(quantity, duck_quantity)

        @pytest.mark.parametrize(
            "duck_quantity",
            [DuckQuantity3(1 * u.mm), DuckQuantity3([1, 2] * u.mm)],
        )
        @pytest.mark.parametrize("out", [None, "empty"])
        def test_full(self, ufunc, quantity, duck_quantity, out):
            out_expected = out
            if out == "empty":
                out = type(duck_quantity)(
                    np.empty_like(ufunc(quantity, duck_quantity.data))
                )
                out_expected = np.empty_like(ufunc(quantity, duck_quantity.data))

            result = ufunc(quantity, duck_quantity, out=out)
            if out is not None:
                assert result is out

            result_expected = ufunc(quantity, duck_quantity.data, out=out_expected)
            assert np.all(result.data == result_expected)


if HAS_SCIPY:
    from scipy import special as sps

    erf_like_ufuncs = (
        sps.erf, sps.erfc, sps.erfcx, sps.erfi,
        sps.gamma, sps.gammaln, sps.loggamma, sps.gammasgn, sps.psi,
        sps.rgamma, sps.digamma, sps.wofz, sps.dawsn,
        sps.entr, sps.exprel, sps.expm1, sps.log1p, sps.exp2, sps.exp10,
    )  # fmt: skip

    if isinstance(sps.erfinv, np.ufunc):
        erf_like_ufuncs += (sps.erfinv, sps.erfcinv)

    def test_scipy_registration():
        """Check that scipy gets loaded upon first use."""
        assert sps.erf not in qh.UFUNC_HELPERS
        sps.erf(1.0 * u.percent)
        assert sps.erf in qh.UFUNC_HELPERS
        if isinstance(sps.erfinv, np.ufunc):
            assert sps.erfinv in qh.UFUNC_HELPERS
        else:
            assert sps.erfinv not in qh.UFUNC_HELPERS

    class TestScipySpecialUfuncs:
        @pytest.mark.parametrize("function", erf_like_ufuncs)
        def test_erf_scalar(self, function):
            TestQuantityMathFuncs.test_exp_scalar(None, function)

        @pytest.mark.parametrize("function", erf_like_ufuncs)
        def test_erf_array(self, function):
            TestQuantityMathFuncs.test_exp_array(None, function)

        @pytest.mark.parametrize("function", erf_like_ufuncs)
        def test_erf_invalid_units(self, function):
            TestQuantityMathFuncs.test_exp_invalid_units(None, function)

        @pytest.mark.parametrize("function", (sps.cbrt,))
        def test_cbrt_scalar(self, function):
            TestQuantityMathFuncs.test_cbrt_scalar(None, function)

        @pytest.mark.parametrize("function", (sps.cbrt,))
        def test_cbrt_array(self, function):
            TestQuantityMathFuncs.test_cbrt_array(None, function)

        @pytest.mark.parametrize("function", (sps.radian,))
        def test_radian(self, function):
            q1 = function(180.0 * u.degree, 0.0 * u.arcmin, 0.0 * u.arcsec)
            assert_allclose(q1.value, np.pi)
            assert q1.unit == u.radian

            q2 = function(0.0 * u.degree, 30.0 * u.arcmin, 0.0 * u.arcsec)
            assert_allclose(q2.value, (30.0 * u.arcmin).to(u.radian).value)
            assert q2.unit == u.radian

            q3 = function(0.0 * u.degree, 0.0 * u.arcmin, 30.0 * u.arcsec)
            assert_allclose(q3.value, (30.0 * u.arcsec).to(u.radian).value)

            # the following doesn't make much sense in terms of the name of the
            # routine, but we check it gives the correct result.
            q4 = function(3.0 * u.radian, 0.0 * u.arcmin, 0.0 * u.arcsec)
            assert_allclose(q4.value, 3.0)
            assert q4.unit == u.radian

            with pytest.raises(TypeError):
                function(3.0 * u.m, 2.0 * u.s, 1.0 * u.kg)

        jv_like_ufuncs = (
            sps.jv, sps.jn, sps.jve, sps.yn, sps.yv, sps.yve, sps.kn, sps.kv,
            sps.kve, sps.iv, sps.ive, sps.hankel1, sps.hankel1e, sps.hankel2,
            sps.hankel2e,
        )  # fmt: skip

        @pytest.mark.parametrize("function", jv_like_ufuncs)
        def test_jv_scalar(self, function):
            q = function(2.0 * u.m / (2.0 * u.m), 3.0 * u.m / (6.0 * u.m))
            assert q.unit == u.dimensionless_unscaled
            assert q.value == function(1.0, 0.5)

        @pytest.mark.parametrize("function", jv_like_ufuncs)
        def test_jv_array(self, function):
            q = function(
                np.ones(3) * u.m / (1.0 * u.m),
                np.array([2.0, 3.0, 6.0]) * u.m / (6.0 * u.m),
            )
            assert q.unit == u.dimensionless_unscaled
            assert np.all(
                q.value == function(np.ones(3), np.array([1.0 / 3.0, 1.0 / 2.0, 1.0]))
            )
            # should also work on quantities that can be made dimensionless
            q2 = function(
                np.ones(3) * u.m / (1.0 * u.m),
                np.array([2.0, 3.0, 6.0]) * u.m / (6.0 * u.cm),
            )
            assert q2.unit == u.dimensionless_unscaled
            assert_allclose(
                q2.value,
                function(np.ones(3), np.array([100.0 / 3.0, 100.0 / 2.0, 100.0])),
            )

        @pytest.mark.parametrize("function", jv_like_ufuncs)
        def test_jv_invalid_units(self, function):
            # Can't use jv() with non-dimensionless quantities
            with pytest.raises(
                TypeError,
                match=(
                    f"Can only apply '{function.__name__}' function to dimensionless"
                    " quantities"
                ),
            ):
                function(1.0 * u.kg, 3.0 * u.m / u.s)
