block.number -> block.timestamp

tweak timing tests

make tests even better

Author: NoahZinsmeister

contracts/UniswapV2Exchange.sol

@@ -16,9 +16,9 @@ contract UniswapV2Exchange is IUniswapV2Exchange, UniswapV2ERC20 {
     address public token0;
     address public token1;
 
-    uint112 private reserve0;        // single storage slot, (jointly) access via getReserves
-    uint112 private reserve1;        // single storage slot, (jointly) access via getReserves
-    uint32  private blockNumberLast; // single storage slot, (jointly) access via getReserves
+    uint112 private reserve0;           // single storage slot, (jointly) access via getReserves
+    uint112 private reserve1;           // single storage slot, (jointly) access via getReserves
+    uint32  private blockTimestampLast; // single storage slot, (jointly) access via getReserves
 
     uint    public  price0CumulativeLast;
     uint    public  price1CumulativeLast;
@@ -52,25 +52,25 @@ contract UniswapV2Exchange is IUniswapV2Exchange, UniswapV2ERC20 {
         token1 = _token1;
     }
 
-    function getReserves() external view returns (uint112 _reserve0, uint112 _reserve1, uint32 _blockNumberLast) {
+    function getReserves() external view returns (uint112 _reserve0, uint112 _reserve1, uint32 _blockTimestampLast) {
         _reserve0 = reserve0;
         _reserve1 = reserve1;
-        _blockNumberLast = blockNumberLast;
+        _blockTimestampLast = blockTimestampLast;
     }
 
     // update reserves and, on the first time this function is called per block, price accumulators
     function _update(uint balance0, uint balance1, uint112 _reserve0, uint112 _reserve1) private {
         require(balance0 <= uint112(-1) && balance1 <= uint112(-1), "UniswapV2: BALANCE_OVERFLOW");
-        uint32 blockNumber = uint32(block.number % 2**32);
-        uint32 blocksElapsed = blockNumber - blockNumberLast; // overflow is desired
-        if (blocksElapsed > 0 && _reserve0 != 0 && _reserve1 != 0) {
+        uint32 blockTimestamp = uint32(block.timestamp % 2**32);
+        uint32 timeElapsed = blockTimestamp - blockTimestampLast; // overflow is desired
+        if (timeElapsed > 0 && _reserve0 != 0 && _reserve1 != 0) {
             // * never overflows, and + overflow is desired
-            price0CumulativeLast += uint(UQ112x112.encode(_reserve1).uqdiv(_reserve0)) * blocksElapsed;
-            price1CumulativeLast += uint(UQ112x112.encode(_reserve0).uqdiv(_reserve1)) * blocksElapsed;
+            price0CumulativeLast += uint(UQ112x112.encode(_reserve1).uqdiv(_reserve0)) * timeElapsed;
+            price1CumulativeLast += uint(UQ112x112.encode(_reserve0).uqdiv(_reserve1)) * timeElapsed;
         }
         reserve0 = uint112(balance0);
         reserve1 = uint112(balance1);
-        blockNumberLast = blockNumber;
+        blockTimestampLast = blockTimestamp;
         emit Sync(reserve0, reserve1);
     }
 

contracts/interfaces/IUniswapV2Exchange.sol

@@ -10,7 +10,7 @@ interface IUniswapV2Exchange {
     function factory() external view returns (address);
     function token0() external view returns (address);
     function token1() external view returns (address);
-    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockNumberLast);
+    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
     function price0CumulativeLast() external view returns (uint);
     function price1CumulativeLast() external view returns (uint);
 

test/UniswapV2Exchange.spec.ts

@@ -3,7 +3,7 @@ import { Contract } from 'ethers'
 import { solidity, MockProvider, createFixtureLoader } from 'ethereum-waffle'
 import { BigNumber, bigNumberify } from 'ethers/utils'
 
-import { expandTo18Decimals, mineBlocks } from './shared/utilities'
+import { expandTo18Decimals, mineBlock } from './shared/utilities'
 import { exchangeFixture } from './shared/fixtures'
 import { AddressZero } from 'ethers/constants'
 
@@ -142,11 +142,13 @@ describe('UniswapV2Exchange', () => {
     await addLiquidity(token0Amount, token1Amount)
 
     // ensure that setting price{0,1}CumulativeLast for the first time doesn't affect our gas math
+    await mineBlock(provider, 1)
     await exchange.sync(overrides)
 
     const swapAmount = expandTo18Decimals(1)
     const expectedOutputAmount = bigNumberify('453305446940074565')
     await token0.transfer(exchange.address, swapAmount)
+    await mineBlock(provider, 1)
     const gasCost = await exchange.estimate.swap(token0.address, expectedOutputAmount, wallet.address, overrides)
     console.log(`Gas required for swap: ${gasCost}`)
   })
@@ -182,16 +184,17 @@ describe('UniswapV2Exchange', () => {
     const token1Amount = expandTo18Decimals(3)
     await addLiquidity(token0Amount, token1Amount)
 
-    const blockNumber = (await exchange.getReserves())[2]
+    const blockTimestamp = (await exchange.getReserves())[2]
     expect(await exchange.price0CumulativeLast()).to.eq(0)
     expect(await exchange.price1CumulativeLast()).to.eq(0)
 
+    await mineBlock(provider, 1)
     await exchange.sync(overrides)
     expect(await exchange.price0CumulativeLast()).to.eq(bigNumberify(2).pow(112))
     expect(await exchange.price1CumulativeLast()).to.eq(bigNumberify(2).pow(112))
-    expect((await exchange.getReserves())[2]).to.eq(blockNumber + 1)
+    expect((await exchange.getReserves())[2]).to.eq(blockTimestamp + 1)
 
-    await mineBlocks(provider, 8)
+    await mineBlock(provider, 9)
     await exchange.sync(overrides)
     expect(await exchange.price0CumulativeLast()).to.eq(
       bigNumberify(2)
@@ -203,6 +206,6 @@ describe('UniswapV2Exchange', () => {
         .pow(112)
         .mul(10)
     )
-    expect((await exchange.getReserves())[2]).to.eq(blockNumber + 10)
+    expect((await exchange.getReserves())[2]).to.eq(blockTimestamp + 10)
   })
 })

test/shared/utilities.ts

@@ -79,10 +79,10 @@ export async function getApprovalDigest(
   )
 }
 
-async function mineBlock(provider: Web3Provider, timestamp?: number): Promise<void> {
-  await new Promise((resolve, reject) => {
+export async function mineBlock(provider: Web3Provider, seconds: number): Promise<void> {
+  await new Promise(async (resolve, reject) => {
     ;(provider._web3Provider.sendAsync as any)(
-      { jsonrpc: '2.0', method: 'evm_mine', params: timestamp ? [timestamp] : [] },
+      { jsonrpc: '2.0', method: 'evm_mine', params: [(await provider.getBlock('latest')).timestamp + seconds] },
       (error: any, result: any): void => {
         if (error) {
           reject(error)
@@ -93,8 +93,3 @@ async function mineBlock(provider: Web3Provider, timestamp?: number): Promise<vo
     )
   })
 }
-
-export async function mineBlocks(provider: Web3Provider, numberOfBlocks: number, timestamp?: number): Promise<void> {
-  await Promise.all([...Array(numberOfBlocks - 1)].map(() => mineBlock(provider)))
-  await mineBlock(provider, timestamp)
-}