Impl custom Debug for TransactionHash

Resolves #104

zebra-chain/src/transaction.rs

@@ -1,6 +1,8 @@
 //! Transaction types.
 
-use std::io;
+use std::{fmt, io};
+
+use hex;
 
 use crate::serialization::{SerializationError, ZcashDeserialize, ZcashSerialize};
 use crate::sha256d_writer::Sha256dWriter;
@@ -9,9 +11,17 @@ use crate::sha256d_writer::Sha256dWriter;
 ///
 /// TODO: I'm pretty sure this is also a SHA256d hash but I haven't
 /// confirmed it yet.
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[derive(Copy, Clone, Eq, PartialEq)]
 pub struct TransactionHash(pub [u8; 32]);
 
+impl fmt::Debug for TransactionHash {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("TransactionHash")
+            .field(&hex::encode(&self.0))
+            .finish()
+    }
+}
+
 impl From<Transaction> for TransactionHash {
     fn from(transaction: Transaction) -> Self {
         let mut hash_writer = Sha256dWriter::default();
@@ -122,3 +132,27 @@ impl ZcashDeserialize for Transaction {
         unimplemented!();
     }
 }
+
+#[cfg(test)]
+mod tests {
+
+    use std::io::Write;
+
+    use super::TransactionHash;
+
+    use crate::sha256d_writer::Sha256dWriter;
+
+    #[test]
+    fn transactionhash_debug() {
+        let preimage = b"foo bar baz";
+        let mut sha_writer = Sha256dWriter::default();
+        let _ = sha_writer.write_all(preimage);
+
+        let hash = TransactionHash(sha_writer.finish());
+
+        assert_eq!(
+            format!("{:?}", hash),
+            "TransactionHash(\"bf46b4b5030752fedac6f884976162bbfb29a9398f104a280b3e34d51b416631\")"
+        );
+    }
+}