Add pairing_with API.

src/tests/engine.rs

@@ -6,6 +6,14 @@ pub fn engine_tests<E: Engine>()
 {
     let mut rng = XorShiftRng::from_seed([0x5dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
     
+    for _ in 0..10 {
+        let a = E::G1::rand(&mut rng).into_affine();
+        let b = E::G2::rand(&mut rng).into_affine();
+
+        assert!(a.pairing_with(&b) == b.pairing_with(&a));
+        assert!(a.pairing_with(&b) == E::pairing(a, b));
+    }
+
     for _ in 0..1000 {
         let z1 = E::G1Affine::zero().prepare();
         let z2 = E::G2Affine::zero().prepare();