new_contents: import unittest
  from mock import Mock, patch
  
  import numpy as np
  
  
  import evapy.distributions as dist
  
  
  class Test_rayleigh_gen(unittest.TestCase):
      def setUp(self):
          self.dist = dist._distns.rayleigh_gen()
  
      def tearDown(self):
          pass
  
      def test_cdf(self):
          calculated = self.dist.cdf(2.5, loc=0.5, scale=np.sqrt(2.))
          expected = -np.expm1(-1.)
          self.assertAlmostEqual(calculated, expected, places=4)
  
      def test_pdf(self):
          calculated = self.dist.pdf(2.5, loc=0.5, scale=np.sqrt(2.))
          expected = np.exp(-1.)
          self.assertAlmostEqual(calculated, expected, places=4)
  
      def test_ppf(self):
          calculated = self.dist.ppf(0.5, loc=0.5, scale=np.sqrt(2.))
          expected = 2.*np.sqrt(np.log(2.)) + 0.5
          self.assertAlmostEqual(calculated, expected, places=4)
  
subject: add test for rayleigh