I have the following class

from math import sqrt

class Vector:

  def __init__(self, x, y, z):   
    self.x = x
    self.y = y
    self.z = z
    
  def __eq__(self, other):   # v == w
        return self.x == other.x and self.y == other.y and self.z == other.z

  def __ne__(self, other):        # v != w
        return not self == other    

  def __repr__(self): 
    return "Vector("   str(self.x)   ", "   str(self.y)   ", "   str(self.z)   ")"

  def __add__(self, other):
    return Vector(self.x   other.x,self.y   other.y,self.z   other.z)

  def __sub__(self, other):
    return Vector(self.x - other.x, self.y - other.y, self.z - other.z)

  def __mul__(self, other):  
    return self.x * other.x   self.y * other.y   self.z * other.z
  
  def cross(self, other):
    return Vector(self.y * other.z - self.z * other.y,self.z * other.x - self.x * other.z,self.x * other.y - self.y * other.x)

  def length(self):
    return sqrt(self.x ** 2   self.y ** 2   self.z ** 2)

  def __hash__(self): 
    return hash((self.x, self.y, self.z))

on which I am trying to use the unittest function as follows:

class TestVector(unittest.TestCase):
    # test function to test equality of two value
    
    def test_vector_equality(self):
        A = [1, 2, 3]
        B = [1, 2, 3]
        # error message in case if test case got failed
        #message = "First value and second value are not equal!"
        self.assertTrue(A == B)
        
    def test_vector_inequality(self):
        A = [1, 2, 3]
        B = [1,-2,-3]
        self.assertFalse(A == B)  
    
    def test_vector_addition(self):
        A = [1, 2, 3]
        B = [1, 2, 3]
        result = [2, 4, 6]
        self.assertEqual([x   y for x, y in zip(A, B)], result) 

    def test_vector_mulitplication(self):
        A = [1, 2, 3]
        B = [1, 2, 3]
        result = [1, 4, 9]
        self.assertEqual([x*y for x, y in zip(A, B)], result)
    
    def test_vector_subtraction(self):
        A = [1, 2, 3]
        B = [1, 5, 8]
        result = [0, -3, -5]
        self.assertEqual([x - y for x, y in zip(A, B)], result) 
        
    def test_vector_cross_multiplication(self):
        A = [1, 2, 3]
        B = [1, 5, 8]
        result = [1 ,5, 3]
        self.assertEqual([(x[0]*y[1], x[1]*y[0]) for x, y in zip(A, B)], result)
        
    def test_length(self):
        A = [1, 2, 3]
        B = [1, 4, 9] 
        self.assertEqual(B, [i ** 2 for i in A])          
                                                 
if __name__ == "__main__":
    unittest.main(argv=['first-arg-is-ignored'], exit= False) 

It works great for all the tests before the cross multiplication one. I would like to get some suggestions about how to set it. Also, I do not know how to set the hash test. Just let me know if you possibly might suggest some way to fix this.

Thank you so much

CodePudding user response：

Unrelated to the question, but imporant: this is not how you unittest. Tests are expected to use class methods, comparing results with expected ones.

Now the issues with test_vector_cross_multiplication:

• the result should be [1, -5, 3] instead of [1, 5, 3]
• the comprehension [(x[0]*y[1], x[1]*y[0]) for x, y in zip(A, B)] uses indexes on numbers and produces tuples

The correct way to calculate the cross product:

[(A[i]*B[i 1] - B[i]*A[i 1]) for i in range(1-len(A), 1)]