new_contents: import unittest
  
  import numpy as np
  from .. import utils
  from ..utils_c import interp
  
  def test_cinterp():
      """
      Simple interpolation
      """
      xarr = np.array([0.0,1.0,2.0])
      yarr = np.array([0.0,1.0,0.0])
      result = interp.interp_c(np.array([0.5]), xarr, yarr)
      assert(np.allclose(result, 0.5))
  
  
  def test_cinterp_conserve():
      """
      Linear interpolation conserving the integral 
      """
      xarr = np.arange(1., 3., 0.0001)
      yarr = (np.abs(xarr-2.) <= 0.1)*1.
      
      np.random.seed(1)
      xlr = np.random.rand(10)*2+1
      xlr.sort()
      
      ylr = interp.interp_conserve_c(xlr, xarr, yarr)
      
      assert(np.allclose(np.trapz(ylr, xlr), np.trapz(yarr, xarr)))
      
      ylr_slow = interp.interp_conserve(xlr, xarr, yarr)
      assert(np.allclose(np.trapz(ylr_slow, xlr), np.trapz(yarr, xarr)))
      
subject: add basic tests for cythonized interp utils