integration-tests: fix timestamp assertion

Update the assertion to not expect that the timestamps are
exactly equal but instead assert that the values are within
5%. This is because now the timestamps in L2 no longer
correspond to L1 timestamps and may be updated arbitrarily
by the sequencer.

integration-tests/test/ovmcontext.spec.ts

@@ -2,7 +2,7 @@ import { expect } from './shared/setup'
 
 /* Imports: External */
 import { ethers } from 'hardhat'
-import { injectL2Context } from '@eth-optimism/core-utils'
+import { injectL2Context, expectApprox } from '@eth-optimism/core-utils'
 import { predeploys } from '@eth-optimism/contracts'
 import { Contract, BigNumber } from 'ethers'
 
@@ -74,9 +74,11 @@ describe('OVM Context: Layer 2 EVM Context', () => {
       const l1BlockNumber = await OVMContextStorage.l1BlockNumbers(i)
       expect(l1BlockNumber.toNumber()).to.deep.equal(l1Block.number)
 
-      // L1 and L2 blocks will have the same timestamp.
+      // L1 and L2 blocks will have approximately the same timestamp.
       const timestamp = await OVMContextStorage.timestamps(i)
-      expect(timestamp.toNumber()).to.deep.equal(l1Block.timestamp)
+      expectApprox(timestamp.toNumber(), l1Block.timestamp, {
+        percentUpperDeviation: 5,
+      })
       expect(timestamp.toNumber()).to.deep.equal(l2Block.timestamp)
 
       // Difficulty should always be zero.

integration-tests/test/shared/env.ts

@@ -33,6 +33,7 @@ export class OptimismEnv {
   addressManager: Contract
   l1Bridge: Contract
   l1Messenger: Contract
+  l1BlockNumber: Contract
   ctc: Contract
   scc: Contract
 
@@ -59,6 +60,7 @@ export class OptimismEnv {
     this.addressManager = args.addressManager
     this.l1Bridge = args.l1Bridge
     this.l1Messenger = args.l1Messenger
+    this.l1BlockNumber = args.l1BlockNumber
     this.ovmEth = args.ovmEth
     this.l2Bridge = args.l2Bridge
     this.l2Messenger = args.l2Messenger
@@ -113,12 +115,17 @@ export class OptimismEnv {
       .connect(l2Wallet)
       .attach(predeploys.OVM_SequencerFeeVault)
 
+    const l1BlockNumber = getContractFactory('iOVM_L1BlockNumber')
+      .connect(l2Wallet)
+      .attach(predeploys.OVM_L1BlockNumber)
+
     return new OptimismEnv({
       addressManager,
       l1Bridge,
       ctc,
       scc,
       l1Messenger,
+      l1BlockNumber,
       ovmEth,
       gasPriceOracle,
       sequencerFeeVault,

integration-tests/test/stress-tests.spec.ts

@@ -211,4 +211,29 @@ describe('stress tests', () => {
       )
     }).timeout(STRESS_TEST_TIMEOUT)
   })
+
+  // These tests depend on an archive node due to the historical `eth_call`s
+  describe('Monotonicity Checks', () => {
+    it('should have monotonic timestamps and l1 blocknumbers', async () => {
+      const tip = await env.l2Provider.getBlock('latest')
+      const prev = {
+        block: await env.l2Provider.getBlock(0),
+        l1BlockNumber: await env.l1BlockNumber.getL1BlockNumber({
+          blockTag: 0,
+        }),
+      }
+      for (let i = 1; i < tip.number; i++) {
+        const block = await env.l2Provider.getBlock(i)
+        expect(block.timestamp).to.be.gte(prev.block.timestamp)
+
+        const l1BlockNumber = await env.l1BlockNumber.getL1BlockNumber({
+          blockTag: i,
+        })
+        expect(l1BlockNumber.gt(prev.l1BlockNumber))
+
+        prev.block = block
+        prev.l1BlockNumber = l1BlockNumber
+      }
+    })
+  })
 })