human
I wrote the below code

    from chainer import gradient_check
    from chainer import testing
    if (func_expected is None):
        name = func.__class__.__name__.lower()
        try:
            func_expected = getattr(numpy, name)
        except AttributeError:
            raise ValueError("NumPy    has    no    functions    corresponding    to    Chainer    function    '{}'.".format(name))
    if (label_expected is None):
        label_expected = func.__class__.__name__.lower()
    if (make_data is None):
        make_data = _make_data_default
    def f(klass):
        assert issubclass(klass, unittest.TestCase)
        def setUp(self):
            (self.x, self.gy) = make_data(self.shape, self.dtype)
            if (self.dtype == numpy.float16):
                self.backward_options = {'eps': (2 ** (-4)), 'atol': (2 ** (-4)), 'rtol': (2 ** (-4)), 'dtype': numpy.float64}
            else:
                self.backward_options = {'atol': 0.0001, 'rtol': 0.0001}
        setattr(klass, 'setUp', setUp)
        def check_forward(self, x_data):
            x = variable.Variable(x_data)
            y = func(x)
            self.assertEqual(y.data.dtype, x_data.dtype)
            y_expected = func_expected(cuda.to_cpu(x_data), dtype=x_data.dtype)
            testing.assert_allclose(y_expected, y.data, atol=0.0001, rtol=0.0001)
        setattr(klass, 'check_forward', check_forward)
        @condition.retry(3)
        def test_forward_cpu(self):
            self.check_forward(self.x)
        setattr(klass, 'test_forward_cpu', test_forward_cpu)
        @attr.gpu
        @condition.retry(3)
        def test_forward_gpu(self):
            self.check_forward(cuda.to_gpu(self.x))
        setattr(klass, 'test_forward_gpu', test_forward_gpu)
        def check_backward(self, x_data, y_grad):
            gradient_check.check_backward(func, x_data, y_grad, **self.backward_options)
        setattr(klass, 'check_backward', check_backward)
        @condition.retry(3)
        def test_backward_cpu(self):
            self.check_backward(self.x,...

What's a good function header?
assistant
#Here's a good function header.

def unary_math_function_unittest(func, func_expected=None, label_expected=None, make_data=None):