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`visitDifferences` had no test coverage: `LedgerMaster::populateFetchPack` is its only caller, and nothing exercised that path, so the private `hasLeafNode` and `hasInnerNode` it consults were untested too. Codecov flagged the resulting gap against an unrelated refactor, since that commit happened to touch a line inside `hasLeafNode`. Four cases: a map missing one item reports only the nodes on that item's path, an identical map reports nothing, a null comparison map reports every node the plain `visitNodes` walk sees, and a callback returning false stops the walk where `populateFetchPack` would stop once a pack is full. The first case uses 64 shared items rather than a couple, so the shared leaves build inner nodes of their own and the walk has whole matching subtrees to skip. Verified by mutation: with only two shared items, breaking `hasInnerNode` to always claim a match left every test passing, since the tree was too shallow for that branch to be taken. It also asserts that some inner nodes are reported but not all, which is what distinguishes skipping a subtree from walking it. Breaking `hasLeafNode` in either direction, or `hasInnerNode`, now fails the case. The maps are hashed via `getHash` before being compared, since node hashes are computed on demand and `visitDifferences` returns early while the root hash is still zero. Without that the walk visits nothing and every assertion here would hold vacuously.