Auto merge of #18 - ebfull:primefieldreprtests, r=ebfull

Random encoding/decoding tests for `PrimeFieldRepr`

src/bls12_381/fq.rs

@@ -1750,3 +1750,8 @@ fn test_fq_ordering() {
         assert!(Fq::from_repr(FqRepr::from(i+1)).unwrap() > Fq::from_repr(FqRepr::from(i)).unwrap());
     }
 }
+
+#[test]
+fn fq_repr_tests() {
+    ::tests::repr::random_repr_tests::<FqRepr>();
+}

src/bls12_381/fr.rs

@@ -1453,3 +1453,8 @@ fn fr_field_tests() {
     ::tests::field::random_sqrt_tests::<Fr>();
     ::tests::field::random_frobenius_tests::<Fr, _>(Fr::char(), 13);
 }
+
+#[test]
+fn fr_repr_tests() {
+    ::tests::repr::random_repr_tests::<FrRepr>();
+}

src/lib.rs

@@ -332,6 +332,7 @@ pub trait PrimeFieldRepr: Sized +
                           Ord +
                           Send +
                           Sync +
+                          Default +
                           fmt::Debug +
                           fmt::Display +
                           'static +

src/tests/mod.rs

@@ -1,3 +1,4 @@
 pub mod curve;
 pub mod field;
 pub mod engine;
+pub mod repr;

src/tests/repr.rs

@@ -0,0 +1,21 @@
+use rand::{SeedableRng, XorShiftRng};
+use ::{PrimeFieldRepr};
+
+pub fn random_repr_tests<R: PrimeFieldRepr>() {
+	random_encoding_tests::<R>();
+}
+
+fn random_encoding_tests<R: PrimeFieldRepr>() {
+	let mut rng = XorShiftRng::from_seed([0x5dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
+
+	for _ in 0..1000 {
+		let r = R::rand(&mut rng);
+		let mut rdecoded = R::default();
+
+		let mut v: Vec<u8> = vec![];
+		r.write_be(&mut v).unwrap();
+		rdecoded.read_be(&v[0..]).unwrap();
+
+		assert_eq!(r, rdecoded);
+	}
+}