more test coverage for ellipticurve module

Author: tomato42

src/ecdsa/ellipticcurve.py

@@ -1532,7 +1532,9 @@ def double(self):
 
         X3, Y3, Z3, T3 = self._double(X1, Y1, Z1, T1, p, a)
 
-        if not X3 or not T3:
+        # both Ed25519 and Ed448 have prime order, so no point added to
+        # itself will equal zero
+        if not X3 or not T3:  # pragma: no branch
             return INFINITY
         return PointEdwards(self.__curve, X3, Y3, Z3, T3, self.__order)
 

src/ecdsa/test_ecdh.py

@@ -32,7 +32,7 @@
 from .ellipticcurve import CurveEdTw
 
 
-if "--fast" in sys.argv:
+if "--fast" in sys.argv:  # pragma: no cover
     curves = [SECP112r2, SECP128r1]
 
 

src/ecdsa/test_eddsa.py

@@ -163,6 +163,27 @@ def test_ed25519_eq_x_different_y():
     assert a != b
 
 
+def test_ed25519_mul_by_order():
+    g = PointEdwards(
+        curve_ed25519,
+        generator_ed25519.x(),
+        generator_ed25519.y(),
+        1,
+        generator_ed25519.x() * generator_ed25519.y(),
+    )
+
+    assert g * generator_ed25519.order() == INFINITY
+
+
+def test_radd():
+
+    a = PointEdwards(curve_ed25519, 1, 1, 1, 1)
+
+    p = INFINITY + a
+
+    assert p == a
+
+
 def test_ed25519_test_normalisation_and_scaling():
     x = generator_ed25519.x()
     y = generator_ed25519.y()

src/ecdsa/test_ellipticcurve.py

@@ -223,3 +223,34 @@ def test_inequality_points(self):
     def test_inequality_points_diff_types(self):
         c = CurveFp(100, -3, 100)
         self.assertNotEqual(self.g_23, c)
+
+    def test_to_bytes_from_bytes(self):
+        p = Point(self.c_23, 3, 10)
+
+        self.assertEqual(p, Point.from_bytes(self.c_23, p.to_bytes()))
+
+    def test_add_to_neg_self(self):
+        p = Point(self.c_23, 3, 10)
+
+        self.assertEqual(INFINITY, p + (-p))
+
+    def test_add_to_infinity(self):
+        p = Point(self.c_23, 3, 10)
+
+        self.assertIs(p, p + INFINITY)
+
+    def test_mul_infinity_by_scalar(self):
+        self.assertIs(INFINITY, INFINITY * 10)
+
+    def test_mul_by_negative(self):
+        p = Point(self.c_23, 3, 10)
+
+        self.assertEqual(p * -5, (-p) * 5)
+
+    def test_str_infinity(self):
+        self.assertEqual(str(INFINITY), "infinity")
+
+    def test_str_point(self):
+        p = Point(self.c_23, 3, 10)
+
+        self.assertEqual(str(p), "(3,10)")

src/ecdsa/test_jacobi.py

@@ -635,6 +635,12 @@ def test_equality_with_wrong_curves(self):
 
         self.assertNotEqual(p_a, p_b)
 
+    def test_add_with_point_at_infinity(self):
+        pj1 = PointJacobi(curve=CurveFp(23, 1, 1, 1), x=2, y=3, z=1, order=1)
+        x, y, z = pj1._add(2, 3, 1, 5, 5, 0, 23)
+
+        self.assertEqual((x, y, z), (2, 3, 1))
+
     def test_pickle(self):
         pj = PointJacobi(curve=CurveFp(23, 1, 1, 1), x=2, y=3, z=1, order=1)
         self.assertEqual(pickle.loads(pickle.dumps(pj)), pj)