[added] coverage for getMerkleTreeProof

.changeset/sharp-dancers-clap.md

+---
+'@eth-optimism/message-relayer': patch
+---
+
+added coverage for getMerkleTreeProof

packages/message-relayer/src/relay-tx.ts

@@ -258,7 +258,10 @@ export const getStateRootBatchByTransactionIndex = async (
  * @param index Index to generate a proof for.
  * @returns Merkle proof sibling leaves, as hex strings.
  */
-const getMerkleTreeProof = (leaves: string[], index: number): string[] => {
+export const getMerkleTreeProof = (
+  leaves: string[],
+  index: number
+): string[] => {
   // Our specific Merkle tree implementation requires that the number of leaves is a power of 2.
   // If the number of given leaves is less than a power of 2, we need to round up to the next
   // available power of 2. We fill the remaining space with the hash of bytes32(0).

packages/message-relayer/test/unit-tests/relay-tx.spec.ts

@@ -9,6 +9,7 @@ import { toPlainObject } from 'lodash'
 
 /* Imports: Internal */
 import {
+  getMerkleTreeProof,
   getMessagesAndProofsForL2Transaction,
   getStateRootBatchByTransactionIndex,
   getStateBatchAppendedEventByTransactionIndex,
@@ -375,3 +376,37 @@ describe('relay transaction generation functions', () => {
     })
   })
 })
+
+describe('getMerkleTreeProof', () => {
+  let leaves: string[] = [
+    'the',
+    'quick',
+    'brown',
+    'fox',
+    'jumps',
+    'over',
+    'the',
+    'lazy',
+    'dog',
+  ]
+  const index: number = 4
+  it('should generate a merkle tree proof from an odd number of leaves at the correct index', () => {
+    const expectedProof = [
+      '0x6f766572',
+      '0x123268ec1a3f9aac2bc68e899fe4329eefef783c76265722508b8abbfbf11440',
+      '0x12aaa1b2e09f26e14d86aa3b157b94cfeabe815e44b6742d00c47441a576b12d',
+      '0x297d90df3f77f93eefdeab4e9f6e9a074b41a3508f9d265e92e9b5449c7b11c8',
+    ]
+    expect(getMerkleTreeProof(leaves, index)).to.deep.equal(expectedProof)
+  })
+
+  it('should generate a merkle tree proof from an even number of leaves at the correct index', () => {
+    const expectedProof = [
+      '0x6f766572',
+      '0x09e430fa7b513203dd9c74afd734267a73f64299d9dac61ef09e96c3b3b3fe96',
+      '0x12aaa1b2e09f26e14d86aa3b157b94cfeabe815e44b6742d00c47441a576b12d',
+    ]
+    leaves = leaves.slice(0, leaves.length - 2)
+    expect(getMerkleTreeProof(leaves, index)).to.deep.equal(expectedProof)
+  })
+})