Merge pull request #139 from 0xPolygonMiden/hacka-support-adding-existing-structures-to-store

store: support adding existing structures

benches/store.rs

@@ -34,7 +34,7 @@ fn get_empty_leaf_simplesmt(c: &mut Criterion) {
     // both SMT and the store are pre-populated with empty hashes, accessing these values is what is
     // being benchmarked here, so no values are inserted into the backends
     let smt = SimpleSmt::new(depth).unwrap();
-    let store = MerkleStore::new();
+    let store = MerkleStore::from(&smt);
     let root = smt.root();
 
     group.bench_function(BenchmarkId::new("SimpleSmt", depth), |b| {
@@ -66,7 +66,7 @@ fn get_leaf_merkletree(c: &mut Criterion) {
 
         let mtree_leaves: Vec<Word> = leaves.iter().map(|v| v.into()).collect();
         let mtree = MerkleTree::new(mtree_leaves.clone()).unwrap();
-        let store = MerkleStore::new().with_merkle_tree(mtree_leaves).unwrap();
+        let store = MerkleStore::from(&mtree);
         let depth = mtree.depth();
         let root = mtree.root();
         let size_u64 = size as u64;
@@ -108,9 +108,7 @@ fn get_leaf_simplesmt(c: &mut Criterion) {
             .unwrap()
             .with_leaves(smt_leaves.clone())
             .unwrap();
-        let store = MerkleStore::new()
+        let store = MerkleStore::from(&smt);
-            .with_sparse_merkle_tree(SimpleSmt::MAX_DEPTH, smt_leaves)
-            .unwrap();
         let depth = smt.depth();
         let root = smt.root();
         let size_u64 = size as u64;
@@ -143,7 +141,7 @@ fn get_node_of_empty_simplesmt(c: &mut Criterion) {
     // of these values is what is being benchmarked here, so no values are inserted into the
     // backends.
     let smt = SimpleSmt::new(depth).unwrap();
-    let store = MerkleStore::new();
+    let store = MerkleStore::from(&smt);
     let root = smt.root();
     let half_depth = depth / 2;
     let half_size = 2_u64.pow(half_depth as u32);
@@ -178,7 +176,7 @@ fn get_node_merkletree(c: &mut Criterion) {
 
         let mtree_leaves: Vec<Word> = leaves.iter().map(|v| v.into()).collect();
         let mtree = MerkleTree::new(mtree_leaves.clone()).unwrap();
-        let store = MerkleStore::new().with_merkle_tree(mtree_leaves).unwrap();
+        let store = MerkleStore::from(&mtree);
         let root = mtree.root();
         let half_depth = mtree.depth() / 2;
         let half_size = 2_u64.pow(half_depth as u32);
@@ -221,9 +219,7 @@ fn get_node_simplesmt(c: &mut Criterion) {
             .unwrap()
             .with_leaves(smt_leaves.clone())
             .unwrap();
-        let store = MerkleStore::new()
+        let store = MerkleStore::from(&smt);
-            .with_sparse_merkle_tree(SimpleSmt::MAX_DEPTH, smt_leaves)
-            .unwrap();
         let root = smt.root();
         let half_depth = smt.depth() / 2;
         let half_size = 2_u64.pow(half_depth as u32);
@@ -258,7 +254,7 @@ fn get_leaf_path_merkletree(c: &mut Criterion) {
 
         let mtree_leaves: Vec<Word> = leaves.iter().map(|v| v.into()).collect();
         let mtree = MerkleTree::new(mtree_leaves.clone()).unwrap();
-        let store = MerkleStore::new().with_merkle_tree(mtree_leaves).unwrap();
+        let store = MerkleStore::from(&mtree);
         let depth = mtree.depth();
         let root = mtree.root();
         let size_u64 = size as u64;
@@ -300,9 +296,7 @@ fn get_leaf_path_simplesmt(c: &mut Criterion) {
             .unwrap()
             .with_leaves(smt_leaves.clone())
             .unwrap();
-        let store = MerkleStore::new()
+        let store = MerkleStore::from(&smt);
-            .with_sparse_merkle_tree(SimpleSmt::MAX_DEPTH, smt_leaves)
-            .unwrap();
         let depth = smt.depth();
         let root = smt.root();
         let size_u64 = size as u64;
@@ -347,10 +341,13 @@ fn new(c: &mut Criterion) {
 
         // This could be done with `bench_with_input`, however to remove variables while comparing
         // with MerkleTree it is using `iter_batched`
-        group.bench_function(BenchmarkId::new("MerkleStore::with_merkle_tree", size), |b| {
+        group.bench_function(BenchmarkId::new("MerkleStore::extend::MerkleTree", size), |b| {
             b.iter_batched(
                 || leaves.iter().map(|v| v.into()).collect::<Vec<Word>>(),
-                |l| black_box(MerkleStore::new().with_merkle_tree(l)),
+                |l| {
+                    let mtree = MerkleTree::new(l).unwrap();
+                    black_box(MerkleStore::from(&mtree));
+                },
                 BatchSize::SmallInput,
             )
         });
@@ -369,7 +366,7 @@ fn new(c: &mut Criterion) {
             )
         });
 
-        group.bench_function(BenchmarkId::new("MerkleStore::with_sparse_merkle_tree", size), |b| {
+        group.bench_function(BenchmarkId::new("MerkleStore::extend::SimpleSmt", size), |b| {
             b.iter_batched(
                 || {
                     leaves
@@ -378,7 +375,10 @@ fn new(c: &mut Criterion) {
                         .map(|(c, v)| (c.try_into().unwrap(), v.into()))
                         .collect::<Vec<(u64, Word)>>()
                 },
-                |l| black_box(MerkleStore::new().with_sparse_merkle_tree(SimpleSmt::MAX_DEPTH, l)),
+                |l| {
+                    let smt = SimpleSmt::new(SimpleSmt::MAX_DEPTH).unwrap().with_leaves(l).unwrap();
+                    black_box(MerkleStore::from(&smt));
+                },
                 BatchSize::SmallInput,
             )
         });
@@ -397,7 +397,7 @@ fn update_leaf_merkletree(c: &mut Criterion) {
 
         let mtree_leaves: Vec<Word> = leaves.iter().map(|v| v.into()).collect();
         let mut mtree = MerkleTree::new(mtree_leaves.clone()).unwrap();
-        let mut store = MerkleStore::new().with_merkle_tree(mtree_leaves).unwrap();
+        let mut store = MerkleStore::from(&mtree);
         let depth = mtree.depth();
         let root = mtree.root();
         let size_u64 = size as u64;
@@ -446,9 +446,7 @@ fn update_leaf_simplesmt(c: &mut Criterion) {
             .unwrap()
             .with_leaves(smt_leaves.clone())
             .unwrap();
-        let mut store = MerkleStore::new()
+        let mut store = MerkleStore::from(&smt);
-            .with_sparse_merkle_tree(SimpleSmt::MAX_DEPTH, smt_leaves)
-            .unwrap();
         let depth = smt.depth();
         let root = smt.root();
         let size_u64 = size as u64;

src/merkle/merkle_tree.rs

@@ -150,9 +150,11 @@ impl MerkleTree {
         Ok(())
     }
 
-    /// An iterator over every inner node in the tree. The iterator order is unspecified.
+    /// Returns n iterator over every inner node of this [MerkleTree].
-    pub fn inner_nodes(&self) -> MerkleTreeNodes<'_> {
+    ///
-        MerkleTreeNodes {
+    /// The iterator order is unspecified.
+    pub fn inner_nodes(&self) -> InnerNodeIterator<'_> {
+        InnerNodeIterator {
             nodes: &self.nodes,
             index: 1, // index 0 is just padding, start at 1
         }
@@ -165,12 +167,12 @@ impl MerkleTree {
 /// An iterator over every inner node of the [MerkleTree].
 ///
 /// Use this to extract the data of the tree, there is no guarantee on the order of the elements.
-pub struct MerkleTreeNodes<'a> {
+pub struct InnerNodeIterator<'a> {
     nodes: &'a Vec<Word>,
     index: usize,
 }
 
-impl<'a> Iterator for MerkleTreeNodes<'a> {
+impl<'a> Iterator for InnerNodeIterator<'a> {
     type Item = InnerNodeInfo;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -192,6 +194,9 @@ impl<'a> Iterator for MerkleTreeNodes<'a> {
     }
 }
 
+// UTILITY FUNCTIONS
+// ================================================================================================
+
 /// Utility to visualize a [MerkleTree] in text.
 pub fn tree_to_text(tree: &MerkleTree) -> Result<String, fmt::Error> {
     let indent = "  ";

src/merkle/path.rs

@@ -1,4 +1,4 @@
-use super::{vec, MerkleError, NodeIndex, Rpo256, Vec, Word};
+use super::{vec, InnerNodeInfo, MerkleError, NodeIndex, Rpo256, Vec, Word};
 use core::ops::{Deref, DerefMut};
 
 // MERKLE PATH
@@ -22,6 +22,11 @@ impl MerklePath {
     // PROVIDERS
     // --------------------------------------------------------------------------------------------
 
+    /// Returns the depth in which this Merkle path proof is valid.
+    pub fn depth(&self) -> u8 {
+        self.nodes.len() as u8
+    }
+
     /// Computes the merkle root for this opening.
     pub fn compute_root(&self, index: u64, node: Word) -> Result<Word, MerkleError> {
         let mut index = NodeIndex::new(self.depth(), index)?;
@@ -34,11 +39,6 @@ impl MerklePath {
         Ok(root)
     }
 
-    /// Returns the depth in which this Merkle path proof is valid.
-    pub fn depth(&self) -> u8 {
-        self.nodes.len() as u8
-    }
-
     /// Verifies the Merkle opening proof towards the provided root.
     ///
     /// Returns `true` if `node` exists at `index` in a Merkle tree with `root`.
@@ -48,6 +48,20 @@ impl MerklePath {
             Err(_) => false,
         }
     }
+
+    /// Returns an iterator over every inner node of this [MerklePath].
+    ///
+    /// The iteration order is unspecified.
+    ///
+    /// # Errors
+    /// Returns an error if the specified index is not valid for this path.
+    pub fn inner_nodes(&self, index: u64, node: Word) -> Result<InnerNodeIterator, MerkleError> {
+        Ok(InnerNodeIterator {
+            nodes: &self.nodes,
+            index: NodeIndex::new(self.depth(), index)?,
+            value: node,
+        })
+    }
 }
 
 impl From<Vec<Word>> for MerklePath {
@@ -72,6 +86,9 @@ impl DerefMut for MerklePath {
     }
 }
 
+// ITERATORS
+// ================================================================================================
+
 impl FromIterator<Word> for MerklePath {
     fn from_iter<T: IntoIterator<Item = Word>>(iter: T) -> Self {
         Self::new(iter.into_iter().collect())
@@ -87,6 +104,39 @@ impl IntoIterator for MerklePath {
     }
 }
 
+/// An iterator over internal nodes of a [MerklePath].
+pub struct InnerNodeIterator<'a> {
+    nodes: &'a Vec<Word>,
+    index: NodeIndex,
+    value: Word,
+}
+
+impl<'a> Iterator for InnerNodeIterator<'a> {
+    type Item = InnerNodeInfo;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if !self.index.is_root() {
+            let sibling_pos = self.nodes.len() - self.index.depth() as usize;
+            let (left, right) = if self.index.is_value_odd() {
+                (self.nodes[sibling_pos], self.value)
+            } else {
+                (self.value, self.nodes[sibling_pos])
+            };
+
+            self.value = Rpo256::merge(&[left.into(), right.into()]).into();
+            self.index.move_up();
+
+            Some(InnerNodeInfo {
+                value: self.value,
+                left,
+                right,
+            })
+        } else {
+            None
+        }
+    }
+}
+
 // MERKLE PATH CONTAINERS
 // ================================================================================================
 
@@ -110,3 +160,25 @@ pub struct RootPath {
     /// The path from `value` to `root` (exclusive).
     pub path: MerklePath,
 }
+
+// TESTS
+// ================================================================================================
+
+#[cfg(test)]
+mod tests {
+    use crate::merkle::{int_to_node, MerklePath};
+
+    #[test]
+    fn test_inner_nodes() {
+        let nodes = vec![int_to_node(1), int_to_node(2), int_to_node(3), int_to_node(4)];
+        let merkle_path = MerklePath::new(nodes);
+
+        let index = 6;
+        let node = int_to_node(5);
+        let root = merkle_path.compute_root(index, node).unwrap();
+
+        let inner_root = merkle_path.inner_nodes(index, node).unwrap().last().unwrap().value;
+
+        assert_eq!(root, inner_root);
+    }
+}

src/merkle/store/mod.rs

@@ -1,7 +1,7 @@
-use super::mmr::{Mmr, MmrPeaks};
+use super::mmr::Mmr;
 use super::{
-    BTreeMap, EmptySubtreeRoots, MerkleError, MerklePath, MerklePathSet, MerkleTree, NodeIndex,
+    BTreeMap, EmptySubtreeRoots, InnerNodeInfo, MerkleError, MerklePath, MerklePathSet, MerkleTree,
-    RootPath, Rpo256, RpoDigest, SimpleSmt, ValuePath, Vec, Word,
+    NodeIndex, RootPath, Rpo256, RpoDigest, SimpleSmt, ValuePath, Vec, Word,
 };
 use crate::utils::{ByteReader, ByteWriter, Deserializable, DeserializationError, Serializable};
 
@@ -47,9 +47,13 @@ pub struct Node {
 /// // the store is initialized with the SMT empty nodes
 /// assert_eq!(store.num_internal_nodes(), 255);
 ///
+/// let tree1 = MerkleTree::new(vec![A, B, C, D, E, F, G, H0]).unwrap();
+/// let tree2 = MerkleTree::new(vec![A, B, C, D, E, F, G, H1]).unwrap();
+///
 /// // populates the store with two merkle trees, common nodes are shared
-/// store.add_merkle_tree([A, B, C, D, E, F, G, H0]);
+/// store
-/// store.add_merkle_tree([A, B, C, D, E, F, G, H1]);
+///     .extend(tree1.inner_nodes())
+///     .extend(tree2.inner_nodes());
 ///
 /// // every leaf except the last are the same
 /// for i in 0..7 {
@@ -111,60 +115,6 @@ impl MerkleStore {
         MerkleStore { nodes }
     }
 
-    /// Appends the provided merkle tree represented by its `leaves` to the set.
-    pub fn with_merkle_tree<I>(mut self, leaves: I) -> Result<Self, MerkleError>
-    where
-        I: IntoIterator<Item = Word>,
-    {
-        self.add_merkle_tree(leaves)?;
-        Ok(self)
-    }
-
-    /// Appends the provided Sparse Merkle tree represented by its `entries` to the set.
-    ///
-    /// For more information, check [MerkleStore::add_sparse_merkle_tree].
-    pub fn with_sparse_merkle_tree<R, I>(
-        mut self,
-        depth: u8,
-        entries: R,
-    ) -> Result<Self, MerkleError>
-    where
-        R: IntoIterator<IntoIter = I>,
-        I: Iterator<Item = (u64, Word)> + ExactSizeIterator,
-    {
-        self.add_sparse_merkle_tree(depth, entries)?;
-        Ok(self)
-    }
-
-    /// Appends the provided merkle path set.
-    pub fn with_merkle_path(
-        mut self,
-        index_value: u64,
-        node: Word,
-        path: MerklePath,
-    ) -> Result<Self, MerkleError> {
-        self.add_merkle_path(index_value, node, path)?;
-        Ok(self)
-    }
-
-    /// Appends the provided merkle path set.
-    pub fn with_merkle_paths<I>(mut self, paths: I) -> Result<Self, MerkleError>
-    where
-        I: IntoIterator<Item = (u64, Word, MerklePath)>,
-    {
-        self.add_merkle_paths(paths)?;
-        Ok(self)
-    }
-
-    /// Appends the provided [Mmr] represented by its `leaves` to the set.
-    pub fn with_mmr<I>(mut self, leaves: I) -> Result<Self, MerkleError>
-    where
-        I: IntoIterator<Item = Word>,
-    {
-        self.add_mmr(leaves)?;
-        Ok(self)
-    }
-
     // PUBLIC ACCESSORS
     // --------------------------------------------------------------------------------------------
 
@@ -310,68 +260,21 @@ impl MerkleStore {
     // STATE MUTATORS
     // --------------------------------------------------------------------------------------------
 
-    /// Adds all the nodes of a Merkle tree represented by `leaves`.
+    /// Adds a sequence of nodes yielded by the provided iterator into the store.
-    ///
+    pub fn extend<I>(&mut self, iter: I) -> &mut MerkleStore
-    /// This will instantiate a Merkle tree using `leaves` and include all the nodes into the
-    /// store.
-    ///
-    /// # Errors
-    ///
-    /// This method may return the following errors:
-    /// - `DepthTooSmall` if leaves is empty or contains only 1 element
-    /// - `NumLeavesNotPowerOfTwo` if the number of leaves is not a power-of-two
-    pub fn add_merkle_tree<I>(&mut self, leaves: I) -> Result<Word, MerkleError>
     where
-        I: IntoIterator<Item = Word>,
+        I: Iterator<Item = InnerNodeInfo>,
     {
-        let leaves: Vec<_> = leaves.into_iter().collect();
+        for node in iter {
-        if leaves.len() < 2 {
+            let value: RpoDigest = node.value.into();
-            return Err(MerkleError::DepthTooSmall(leaves.len() as u8));
+            let left: RpoDigest = node.left.into();
+            let right: RpoDigest = node.right.into();
+
+            debug_assert_eq!(Rpo256::merge(&[left, right]), value);
+            self.nodes.insert(value, Node { left, right });
         }
 
-        let tree = MerkleTree::new(leaves)?;
+        self
-        for node in tree.inner_nodes() {
-            self.nodes.insert(
-                node.value.into(),
-                Node {
-                    left: node.left.into(),
-                    right: node.right.into(),
-                },
-            );
-        }
-
-        Ok(tree.root())
-    }
-
-    /// Adds a Sparse Merkle tree defined by the specified `entries` to the store, and returns the
-    /// root of the added tree.
-    ///
-    /// The entries are expected to contain tuples of `(index, node)` describing nodes in the tree
-    /// at `depth`.
-    ///
-    /// # Errors
-    /// Returns an error if the provided `depth` is greater than [SimpleSmt::MAX_DEPTH].
-    pub fn add_sparse_merkle_tree<R, I>(
-        &mut self,
-        depth: u8,
-        entries: R,
-    ) -> Result<Word, MerkleError>
-    where
-        R: IntoIterator<IntoIter = I>,
-        I: Iterator<Item = (u64, Word)> + ExactSizeIterator,
-    {
-        let smt = SimpleSmt::new(depth)?.with_leaves(entries)?;
-        for node in smt.inner_nodes() {
-            self.nodes.insert(
-                node.value.into(),
-                Node {
-                    left: node.left.into(),
-                    right: node.right.into(),
-                },
-            );
-        }
-
-        Ok(smt.root())
     }
 
     /// Adds all the nodes of a Merkle path represented by `path`, opening to `node`. Returns the
@@ -381,31 +284,21 @@ impl MerkleStore {
     /// include all the nodes into the store.
     pub fn add_merkle_path(
         &mut self,
-        index_value: u64,
+        index: u64,
-        mut node: Word,
+        node: Word,
         path: MerklePath,
     ) -> Result<Word, MerkleError> {
-        let mut index = NodeIndex::new(path.len() as u8, index_value)?;
+        let root = path.inner_nodes(index, node)?.fold(Word::default(), |_, node| {
+            let value: RpoDigest = node.value.into();
+            let left: RpoDigest = node.left.into();
+            let right: RpoDigest = node.right.into();
 
-        for sibling in path {
+            debug_assert_eq!(Rpo256::merge(&[left, right]), value);
-            let (left, right) = match index.is_value_odd() {
+            self.nodes.insert(value, Node { left, right });
-                true => (sibling, node),
-                false => (node, sibling),
-            };
-            let parent = Rpo256::merge(&[left.into(), right.into()]);
-            self.nodes.insert(
-                parent,
-                Node {
-                    left: left.into(),
-                    right: right.into(),
-                },
-            );
 
-            index.move_up();
+            node.value
-            node = parent.into();
+        });
-        }
+        Ok(root)
-
-        Ok(node)
     }
 
     /// Adds all the nodes of multiple Merkle paths into the store.
@@ -435,25 +328,6 @@ impl MerkleStore {
         Ok(root)
     }
 
-    /// Appends the provided [Mmr] into the store.
-    pub fn add_mmr<I>(&mut self, leaves: I) -> Result<MmrPeaks, MerkleError>
-    where
-        I: IntoIterator<Item = Word>,
-    {
-        let mmr = Mmr::from(leaves);
-        for node in mmr.inner_nodes() {
-            self.nodes.insert(
-                node.value.into(),
-                Node {
-                    left: node.left.into(),
-                    right: node.right.into(),
-                },
-            );
-        }
-
-        Ok(mmr.accumulator())
-    }
-
     /// Sets a node to `value`.
     ///
     /// # Errors
@@ -482,19 +356,57 @@ impl MerkleStore {
     ///
     /// Merges arbitrary values. They may be leafs, nodes, or a mixture of both.
     pub fn merge_roots(&mut self, root1: Word, root2: Word) -> Result<Word, MerkleError> {
-        let root1: RpoDigest = root1.into();
+        let left: RpoDigest = root1.into();
-        let root2: RpoDigest = root2.into();
+        let right: RpoDigest = root2.into();
 
-        let parent: Word = Rpo256::merge(&[root1, root2]).into();
+        let parent = Rpo256::merge(&[left, right]);
-        self.nodes.insert(
+        self.nodes.insert(parent, Node { left, right });
-            parent.into(),
-            Node {
-                left: root1,
-                right: root2,
-            },
-        );
 
-        Ok(parent)
+        Ok(parent.into())
+    }
+}
+
+// CONVERSIONS
+// ================================================================================================
+
+impl From<&MerkleTree> for MerkleStore {
+    fn from(value: &MerkleTree) -> Self {
+        let mut store = MerkleStore::new();
+        store.extend(value.inner_nodes());
+        store
+    }
+}
+
+impl From<&SimpleSmt> for MerkleStore {
+    fn from(value: &SimpleSmt) -> Self {
+        let mut store = MerkleStore::new();
+        store.extend(value.inner_nodes());
+        store
+    }
+}
+
+impl From<&Mmr> for MerkleStore {
+    fn from(value: &Mmr) -> Self {
+        let mut store = MerkleStore::new();
+        store.extend(value.inner_nodes());
+        store
+    }
+}
+
+impl FromIterator<InnerNodeInfo> for MerkleStore {
+    fn from_iter<T: IntoIterator<Item = InnerNodeInfo>>(iter: T) -> Self {
+        let mut store = MerkleStore::new();
+        store.extend(iter.into_iter());
+        store
+    }
+}
+
+// ITERATORS
+// ================================================================================================
+
+impl Extend<InnerNodeInfo> for MerkleStore {
+    fn extend<T: IntoIterator<Item = InnerNodeInfo>>(&mut self, iter: T) {
+        self.extend(iter.into_iter());
     }
 }
 

src/merkle/store/tests.rs

@@ -1,11 +1,11 @@
 use super::*;
 use crate::{
     hash::rpo::Rpo256,
-    merkle::{int_to_node, MerklePathSet},
+    merkle::{int_to_node, MerklePathSet, MerkleTree, SimpleSmt},
     Felt, Word, WORD_SIZE, ZERO,
 };
 
-#[cfg(std)]
+#[cfg(feature = "std")]
 use std::error::Error;
 
 const KEYS4: [u64; 4] = [0, 1, 2, 3];
@@ -15,7 +15,7 @@ const EMPTY: Word = [ZERO; WORD_SIZE];
 #[test]
 fn test_root_not_in_store() -> Result<(), MerkleError> {
     let mtree = MerkleTree::new(LEAVES4.to_vec())?;
-    let store = MerkleStore::default().with_merkle_tree(LEAVES4)?;
+    let store = MerkleStore::from(&mtree);
     assert_eq!(
         store.get_node(LEAVES4[0], NodeIndex::make(mtree.depth(), 0)),
         Err(MerkleError::RootNotInStore(LEAVES4[0])),
@@ -32,10 +32,8 @@ fn test_root_not_in_store() -> Result<(), MerkleError> {
 
 #[test]
 fn test_merkle_tree() -> Result<(), MerkleError> {
-    let mut store = MerkleStore::default();
-
     let mtree = MerkleTree::new(LEAVES4.to_vec())?;
-    store.add_merkle_tree(LEAVES4.to_vec())?;
+    let store = MerkleStore::from(&mtree);
 
     // STORE LEAVES ARE CORRECT ==============================================================
     // checks the leaves in the store corresponds to the expected values
@@ -176,24 +174,20 @@ fn test_leaf_paths_for_empty_trees() -> Result<(), MerkleError> {
 
 #[test]
 fn test_get_invalid_node() {
-    let mut store = MerkleStore::default();
     let mtree = MerkleTree::new(LEAVES4.to_vec()).expect("creating a merkle tree must work");
-    store
+    let store = MerkleStore::from(&mtree);
-        .add_merkle_tree(LEAVES4.to_vec())
-        .expect("adding a merkle tree to the store must work");
     let _ = store.get_node(mtree.root(), NodeIndex::make(mtree.depth(), 3));
 }
 
 #[test]
 fn test_add_sparse_merkle_tree_one_level() -> Result<(), MerkleError> {
-    let mut store = MerkleStore::default();
     let keys2: [u64; 2] = [0, 1];
     let leaves2: [Word; 2] = [int_to_node(1), int_to_node(2)];
-    store.add_sparse_merkle_tree(48, keys2.into_iter().zip(leaves2.into_iter()))?;
     let smt = SimpleSmt::new(1)
         .unwrap()
         .with_leaves(keys2.into_iter().zip(leaves2.into_iter()))
         .unwrap();
+    let store = MerkleStore::from(&smt);
 
     let idx = NodeIndex::make(1, 0);
     assert_eq!(smt.get_node(idx).unwrap(), leaves2[0]);
@@ -208,15 +202,13 @@ fn test_add_sparse_merkle_tree_one_level() -> Result<(), MerkleError> {
 
 #[test]
 fn test_sparse_merkle_tree() -> Result<(), MerkleError> {
-    let mut store = MerkleStore::default();
-    store
-        .add_sparse_merkle_tree(SimpleSmt::MAX_DEPTH, KEYS4.into_iter().zip(LEAVES4.into_iter()))?;
-
     let smt = SimpleSmt::new(SimpleSmt::MAX_DEPTH)
         .unwrap()
         .with_leaves(KEYS4.into_iter().zip(LEAVES4.into_iter()))
         .unwrap();
 
+    let store = MerkleStore::from(&smt);
+
     // STORE LEAVES ARE CORRECT ==============================================================
     // checks the leaves in the store corresponds to the expected values
     assert_eq!(
@@ -472,7 +464,8 @@ fn wont_open_to_different_depth_root() {
     // For this example, the depth of the Merkle tree is 1, as we have only two leaves. Here we
     // attempt to fetch a node on the maximum depth, and it should fail because the root shouldn't
     // exist for the set.
-    let store = MerkleStore::default().with_merkle_tree([a, b]).unwrap();
+    let mtree = MerkleTree::new(vec![a, b]).unwrap();
+    let store = MerkleStore::from(&mtree);
     let index = NodeIndex::root();
     let err = store.get_node(root, index).err().unwrap();
     assert_eq!(err, MerkleError::RootNotInStore(root));
@@ -499,7 +492,8 @@ fn store_path_opens_from_leaf() {
 
     let root = Rpo256::merge(&[m.into(), n.into()]);
 
-    let store = MerkleStore::default().with_merkle_tree([a, b, c, d, e, f, g, h]).unwrap();
+    let mtree = MerkleTree::new(vec![a, b, c, d, e, f, g, h]).unwrap();
+    let store = MerkleStore::from(&mtree);
     let path = store.get_path(root.into(), NodeIndex::make(3, 1)).unwrap().path;
 
     let expected = MerklePath::new([a.into(), j.into(), n.into()].to_vec());
@@ -509,7 +503,7 @@ fn store_path_opens_from_leaf() {
 #[test]
 fn test_set_node() -> Result<(), MerkleError> {
     let mtree = MerkleTree::new(LEAVES4.to_vec())?;
-    let mut store = MerkleStore::default().with_merkle_tree(LEAVES4)?;
+    let mut store = MerkleStore::from(&mtree);
     let value = int_to_node(42);
     let index = NodeIndex::make(mtree.depth(), 0);
     let new_root = store.set_node(mtree.root(), index, value)?.root;
@@ -520,8 +514,8 @@ fn test_set_node() -> Result<(), MerkleError> {
 
 #[test]
 fn test_constructors() -> Result<(), MerkleError> {
-    let store = MerkleStore::new().with_merkle_tree(LEAVES4)?;
     let mtree = MerkleTree::new(LEAVES4.to_vec())?;
+    let store = MerkleStore::from(&mtree);
 
     let depth = mtree.depth();
     let leaves = 2u64.pow(depth.into());
@@ -532,12 +526,11 @@ fn test_constructors() -> Result<(), MerkleError> {
     }
 
     let depth = 32;
-    let store = MerkleStore::default()
-        .with_sparse_merkle_tree(depth, KEYS4.into_iter().zip(LEAVES4.into_iter()))?;
     let smt = SimpleSmt::new(depth)
         .unwrap()
         .with_leaves(KEYS4.into_iter().zip(LEAVES4.into_iter()))
         .unwrap();
+    let store = MerkleStore::from(&smt);
     let depth = smt.depth();
 
     for key in KEYS4 {
@@ -554,12 +547,14 @@ fn test_constructors() -> Result<(), MerkleError> {
         (3, LEAVES4[3], mtree.get_path(NodeIndex::make(d, 3)).unwrap()),
     ];
 
-    let store1 = MerkleStore::default().with_merkle_paths(paths.clone())?;
+    let mut store1 = MerkleStore::default();
-    let store2 = MerkleStore::default()
+    store1.add_merkle_paths(paths.clone())?;
-        .with_merkle_path(0, LEAVES4[0], mtree.get_path(NodeIndex::make(d, 0))?)?
+
-        .with_merkle_path(1, LEAVES4[1], mtree.get_path(NodeIndex::make(d, 1))?)?
+    let mut store2 = MerkleStore::default();
-        .with_merkle_path(2, LEAVES4[2], mtree.get_path(NodeIndex::make(d, 2))?)?
+    store2.add_merkle_path(0, LEAVES4[0], mtree.get_path(NodeIndex::make(d, 0))?)?;
-        .with_merkle_path(3, LEAVES4[3], mtree.get_path(NodeIndex::make(d, 3))?)?;
+    store2.add_merkle_path(1, LEAVES4[1], mtree.get_path(NodeIndex::make(d, 1))?)?;
+    store2.add_merkle_path(2, LEAVES4[2], mtree.get_path(NodeIndex::make(d, 2))?)?;
+    store2.add_merkle_path(3, LEAVES4[3], mtree.get_path(NodeIndex::make(d, 3))?)?;
     let set = MerklePathSet::new(d).with_paths(paths).unwrap();
 
     for key in [0, 1, 2, 3] {
@@ -723,11 +718,12 @@ fn get_leaf_depth_works_with_depth_8() {
     assert_eq!(Err(MerkleError::DepthTooBig(9)), store.get_leaf_depth(root, 8, a));
 }
 
-#[cfg(std)]
+#[cfg(feature = "std")]
 #[test]
 fn test_serialization() -> Result<(), Box<dyn Error>> {
-    let original = MerkleStore::new().with_merkle_tree(LEAVES4)?;
+    let mtree = MerkleTree::new(LEAVES4.to_vec())?;
-    let decoded = MerkleStore::read_from_bytes(&original.to_bytes())?;
+    let store = MerkleStore::from(&mtree);
-    assert_eq!(original, decoded);
+    let decoded = MerkleStore::read_from_bytes(&store.to_bytes()).expect("deserialization failed");
+    assert_eq!(store, decoded);
     Ok(())
 }