feat: add arbitraries (#24)

Add arbitraries and a simple roundtrip test

Author: rklaehn

Cargo.toml

@@ -14,6 +14,17 @@ pre-release-commit-message = "Release {{version}} 🎉🎉"
 no-dev-version = true
 
 [dependencies]
-multihash = "0.10"
+multihash = "0.10.1"
 multibase = "0.8.0"
 unsigned-varint = "0.3"
+
+quickcheck = { version = "0.9.2", optional = true }
+rand = { version = "0.7.3", optional = true }
+
+[dev-dependencies]
+quickcheck = "0.9.2"
+rand = "0.7.3"
+multihash = { version = "0.10.1", features = ["test"] }
+
+[features]
+test = ["quickcheck", "rand"]

src/arb.rs

@@ -0,0 +1,79 @@
+use crate::{Cid, Codec, Prefix, Version};
+use multihash::Multihash;
+use quickcheck::{Arbitrary, Gen};
+use rand::seq::SliceRandom;
+use rand::Rng;
+
+const CODECS: [Codec; 18] = [
+    Codec::Raw,
+    Codec::DagProtobuf,
+    Codec::DagCBOR,
+    Codec::GitRaw,
+    Codec::EthereumBlock,
+    Codec::EthereumBlockList,
+    Codec::EthereumTxTrie,
+    Codec::EthereumTx,
+    Codec::EthereumTxReceiptTrie,
+    Codec::EthereumTxReceipt,
+    Codec::EthereumStateTrie,
+    Codec::EthereumAccountSnapshot,
+    Codec::EthereumStorageTrie,
+    Codec::BitcoinBlock,
+    Codec::BitcoinTx,
+    Codec::ZcashBlock,
+    Codec::ZcashTx,
+    Codec::DagJSON,
+];
+
+const POPULAR: [Codec; 4] = [
+    Codec::Raw,
+    Codec::DagProtobuf,
+    Codec::DagCBOR,
+    Codec::DagJSON,
+];
+
+impl Arbitrary for Codec {
+    fn arbitrary<G: Gen>(g: &mut G) -> Self {
+        // chose the most frequently used codecs more often
+        if g.gen_bool(0.7) {
+            *POPULAR.choose(g).unwrap()
+        } else {
+            *CODECS.choose(g).unwrap()
+        }
+    }
+}
+
+impl Arbitrary for Version {
+    fn arbitrary<G: Gen>(g: &mut G) -> Self {
+        let version = if g.gen_bool(0.7) { 1 } else { 0 };
+        Version::from(version).unwrap()
+    }
+}
+
+impl Arbitrary for Cid {
+    fn arbitrary<G: Gen>(g: &mut G) -> Self {
+        let version: Version = Arbitrary::arbitrary(g);
+        let v0 = version == Version::V0;
+        if v0 {
+            let data: Vec<u8> = Arbitrary::arbitrary(g);
+            let hash = multihash::Sha2_256::digest(&data);
+            Cid::new_v0(hash).expect("sha2_256 is a valid hash for cid v0")
+        } else {
+            let codec: Codec = Arbitrary::arbitrary(g);
+            let hash: Multihash = Arbitrary::arbitrary(g);
+            Cid::new_v1(codec, hash)
+        }
+    }
+}
+
+impl Arbitrary for Prefix {
+    fn arbitrary<G: Gen>(g: &mut G) -> Self {
+        let cid: Cid = Arbitrary::arbitrary(g);
+        Prefix {
+            version: cid.version,
+            codec: cid.codec,
+            mh_type: cid.hash.algorithm(),
+            mh_len: cid.hash.digest().len(),
+        }
+    }
+}

src/lib.rs

@@ -10,6 +10,9 @@ mod error;
 mod prefix;
 mod version;
 
+#[cfg(any(test, feature = "test"))]
+mod arb;
+
 pub use self::cid::Cid;
 pub use self::codec::Codec;
 pub use self::error::{Error, Result};