Add test showing that the witness cache isn't being serialised

src/zcash/IncrementalMerkleTree.hpp

@@ -43,10 +43,19 @@ public:
     Hash empty_root(size_t depth) {
         return empty_roots.at(depth);
     }
+    template <size_t D, typename H>
+    friend bool operator==(const EmptyMerkleRoots<D, H>& a,
+                           const EmptyMerkleRoots<D, H>& b);
 private:
     boost::array<Hash, Depth+1> empty_roots;
 };
 
+template<size_t Depth, typename Hash>
+bool operator==(const EmptyMerkleRoots<Depth, Hash>& a,
+                const EmptyMerkleRoots<Depth, Hash>& b) {
+    return a.empty_roots == b.empty_roots;
+}
+
 template<size_t Depth, typename Hash>
 class IncrementalWitness;
 
@@ -90,6 +99,10 @@ public:
         return emptyroots.empty_root(Depth);
     }
 
+    template <size_t D, typename H>
+    friend bool operator==(const IncrementalMerkleTree<D, H>& a,
+                           const IncrementalMerkleTree<D, H>& b);
+
 private:
     static EmptyMerkleRoots<Depth, Hash> emptyroots;
     boost::optional<Hash> left;
@@ -104,6 +117,15 @@ private:
     void wfcheck() const;
 };
 
+template<size_t Depth, typename Hash>
+bool operator==(const IncrementalMerkleTree<Depth, Hash>& a,
+                const IncrementalMerkleTree<Depth, Hash>& b) {
+    return (a.emptyroots == b.emptyroots &&
+            a.left == b.left &&
+            a.right == b.right &&
+            a.parents == b.parents);
+}
+
 template <size_t Depth, typename Hash>
 class IncrementalWitness {
 friend class IncrementalMerkleTree<Depth, Hash>;
@@ -130,6 +152,10 @@ public:
         cursor_depth = tree.next_depth(filled.size());
     }
 
+    template <size_t D, typename H>
+    friend bool operator==(const IncrementalWitness<D, H>& a,
+                           const IncrementalWitness<D, H>& b);
+
 private:
     IncrementalMerkleTree<Depth, Hash> tree;
     std::vector<Hash> filled;
@@ -139,6 +165,15 @@ private:
     IncrementalWitness(IncrementalMerkleTree<Depth, Hash> tree) : tree(tree) {}
 };
 
+template<size_t Depth, typename Hash>
+bool operator==(const IncrementalWitness<Depth, Hash>& a,
+                const IncrementalWitness<Depth, Hash>& b) {
+    return (a.tree == b.tree &&
+            a.filled == b.filled &&
+            a.cursor == b.cursor &&
+            a.cursor_depth == b.cursor_depth);
+}
+
 class SHA256Compress : public uint256 {
 public:
     SHA256Compress() : uint256() {}