add gas test for nftManager#positions

contracts/test/NonfungiblePositionManagerPositionsGasTest.sol

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity =0.7.6;
+
+import '../NonfungiblePositionManager.sol';
+
+contract NonfungiblePositionManagerPositionsGasTest {
+    NonfungiblePositionManager immutable nonfungiblePositionManager;
+
+    constructor(NonfungiblePositionManager _nonfungiblePositionManager) {
+        nonfungiblePositionManager = _nonfungiblePositionManager;
+    }
+
+    function getGasCostOfPositions(uint256 tokenId) external view returns (uint256) {
+        uint256 gasBefore = gasleft();
+        nonfungiblePositionManager.positions(tokenId);
+        return gasBefore - gasleft();
+    }
+}

test/NonfungiblePositionManager.spec.ts

@@ -9,6 +9,7 @@ import {
   IWETH9,
   IUniswapV3Factory,
   SwapRouter,
+  NonfungiblePositionManagerPositionsGasTest,
 } from '../typechain'
 import completeFixture from './shared/completeFixture'
 import { computePoolAddress } from './shared/computePoolAddress'
@@ -1165,6 +1166,38 @@ describe('NonfungiblePositionManager', () => {
     })
   })
 
+  describe('#positions', async () => {
+    it('gas', async () => {
+      const positionsGasTestFactory = await ethers.getContractFactory('NonfungiblePositionManagerPositionsGasTest')
+      const positionsGasTest = (await positionsGasTestFactory.deploy(
+        nft.address
+      )) as NonfungiblePositionManagerPositionsGasTest
+
+      await nft.createAndInitializePoolIfNecessary(
+        tokens[0].address,
+        tokens[1].address,
+        FeeAmount.MEDIUM,
+        encodePriceSqrt(1, 1)
+      )
+
+      await nft.mint({
+        token0: tokens[0].address,
+        token1: tokens[1].address,
+        tickLower: getMinTick(TICK_SPACINGS[FeeAmount.MEDIUM]),
+        tickUpper: getMaxTick(TICK_SPACINGS[FeeAmount.MEDIUM]),
+        fee: FeeAmount.MEDIUM,
+        recipient: other.address,
+        amount0Desired: 15,
+        amount1Desired: 15,
+        amount0Min: 0,
+        amount1Min: 0,
+        deadline: 10,
+      })
+
+      await snapshotGasCost(positionsGasTest.getGasCostOfPositions(1))
+    })
+  })
+
   describe('fees accounting', () => {
     beforeEach('create two positions', async () => {
       await nft.createAndInitializePoolIfNecessary(

test/__snapshots__/NonfungiblePositionManager.spec.ts.snap

@@ -30,6 +30,8 @@ exports[`NonfungiblePositionManager #permit owned by eoa gas 1`] = `64528`;
 
 exports[`NonfungiblePositionManager #permit owned by verifying contract gas 1`] = `68325`;
 
+exports[`NonfungiblePositionManager #positions gas 1`] = `19890`;
+
 exports[`NonfungiblePositionManager #transferFrom gas 1`] = `79091`;
 
 exports[`NonfungiblePositionManager #transferFrom gas comes from approved 1`] = `67491`;