improve generic polynomial coverage

src/kyber_py/polynomials/polynomials_generic.py

@@ -154,7 +154,7 @@ def __sub__(self, other):
         return self.parent(new_coeffs)
 
     def __rsub__(self, other):
-        return self.__sub__(other)
+        return -self.__sub__(other)
 
     def __isub__(self, other):
         self = self - other

tests/test_polynomial_generic.py

@@ -16,10 +16,27 @@ def test_random_element(self):
             self.assertEqual(len(f.coeffs), self.R.n)
             self.assertTrue(all([c < self.R.q for c in f.coeffs]))
 
+    def test_non_list_error(self):
+        self.assertRaises(TypeError, lambda: self.R("1"))
+
+    def test_long_list_error(self):
+        self.assertRaises(ValueError, lambda: self.R([0] * (self.R.n + 1)))
+
+    def test_string_format(self):
+        self.assertEqual(
+            str(self.R),
+            "Univariate Polynomial Ring in x over Finite Field of size 11 with modulus x^5 + 1",
+        )
+
 
 class TestPolynomial(unittest.TestCase):
     R = PolynomialRing(11, 5)
 
+    def test_getitem(self):
+        x = self.R.gen()
+        self.assertEqual(x[0], 0)
+        self.assertEqual(x[1], 1)
+
     def test_is_zero(self):
         self.assertTrue(self.R(0).is_zero())
         self.assertFalse(self.R(1).is_zero())
@@ -38,6 +55,32 @@ def test_reduce_coefficients(self):
             f = self.R(coeffs).reduce_coefficients()
             self.assertTrue(all([c < self.R.q for c in f.coeffs]))
 
+    def test_equality(self):
+        for _ in range(100):
+            f1 = self.R.random_element()
+            f2 = -f1
+            self.assertEqual(f1, f1)
+            if f1.is_zero():
+                self.assertTrue(f1 == f2)
+            else:
+                self.assertFalse(f1 == f2)
+
+        self.assertTrue(self.R(0) == 0)
+        self.assertTrue(self.R(1) == self.R.q + 1)
+        self.assertTrue(self.R(self.R.q - 1) == -1)
+
+    def test_add_failure(self):
+        f1 = self.R.random_element()
+        self.assertRaises(NotImplementedError, lambda: f1 + "a")
+
+    def test_sub_failure(self):
+        f1 = self.R.random_element()
+        self.assertRaises(NotImplementedError, lambda: f1 - "a")
+
+    def test_pow_failure(self):
+        f1 = self.R.random_element()
+        self.assertRaises(TypeError, lambda: f1 ** "a")
+
     def test_add_polynomials(self):
         zero = self.R(0)
         for _ in range(100):
@@ -49,6 +92,10 @@ def test_add_polynomials(self):
             self.assertEqual(f1 + f2, f2 + f1)
             self.assertEqual(f1 + (f2 + f3), (f1 + f2) + f3)
 
+            f2 = f1
+            f2 += zero
+            self.assertEqual(f1, f2)
+
     def test_sub_polynomials(self):
         zero = self.R(0)
         for _ in range(100):
@@ -58,9 +105,15 @@ def test_sub_polynomials(self):
 
             self.assertEqual(f1 - zero, f1)
             self.assertEqual(f3 - f3, zero)
+            self.assertEqual(f3 - 0, f3)
+            self.assertEqual(0 - f3, -f3)
             self.assertEqual(f1 - f2, -(f2 - f1))
             self.assertEqual(f1 - (f2 - f3), (f1 - f2) + f3)
 
+            f2 = f1
+            f2 -= zero
+            self.assertEqual(f1, f2)
+
     def test_mul_polynomials(self):
         zero = self.R(0)
         one = self.R(1)
@@ -73,6 +126,12 @@ def test_mul_polynomials(self):
             self.assertEqual(f1 * one, f1)
             self.assertEqual(f1 * f2, f2 * f1)
             self.assertEqual(f1 * (f2 * f3), (f1 * f2) * f3)
+            self.assertEqual(2 * f1, f1 + f1)
+            self.assertEqual(2 * f1, f1 * 2)
+
+            f2 = f1
+            f2 *= one
+            self.assertEqual(f1, f2)
 
     def test_pow_polynomials(self):
         one = self.R(1)
@@ -85,6 +144,14 @@ def test_pow_polynomials(self):
             self.assertEqual(f1 * f1 * f1, f1**3)
             self.assertRaises(ValueError, lambda: f1 ** (-1))
 
+    def test_print(self):
+        self.assertEqual(str(self.R(0)), "0")
+        self.assertEqual(str(self.R(1)), "1")
+        self.assertEqual(str(self.R.gen()), "x")
+        self.assertEqual(
+            str(self.R([1, 2, 3, 4, 5])), "1 + 2*x + 3*x^2 + 4*x^3 + 5*x^4"
+        )
+
 
 if __name__ == "__main__":
     unittest.main()