code: def test_increasing_x(self):
      # Test that x is required to be increasing, see gh-8535
      xx = np.arange(10, dtype=float)
      yy = xx**3
      x = np.arange(10, dtype=float)
      x[1] = x[0] - 1.0
      y = x**3
      w = np.ones_like(x)
      # also test LSQUnivariateSpline [which needs explicit knots]
      spl = UnivariateSpline(xx, yy, check_finite=True)
      t = spl.get_knots()[3:4]  # interior knots w/ default k=3
      assert_raises(
          ValueError,
          UnivariateSpline,
          **dict(x=x, y=y, check_finite=True),
      )
      assert_raises(
          ValueError,
          InterpolatedUnivariateSpline,
          **dict(x=x, y=y, check_finite=True),
      )
      assert_raises(
          ValueError,
          LSQUnivariateSpline,
          **dict(x=x, y=y, t=t, w=w, check_finite=True),
      )
  
imports: import numpy
  from numpy.testing import assert_equal, assert_almost_equal, assert_array_equal, assert_array_almost_equal, assert_allclose, suppress_warnings
  from pytest import raises
  from numpy import array, diff, linspace, meshgrid, ones, pi, shape
  from scipy.interpolate.fitpack import bisplrep, bisplev
  from scipy.interpolate.fitpack2 import UnivariateSpline, LSQUnivariateSpline, InterpolatedUnivariateSpline, LSQBivariateSpline, SmoothBivariateSpline, RectBivariateSpline, LSQSphereBivariateSpline, SmoothSphereBivariateSpline, RectSphereBivariateSpline
label_desc: Use image node_id 14 for calling the TestUnivariateSpline obj's underlying member method code with example usage: obj.test_increasing_x() without return types