chore(acceptance): fix potential flake openMarginalVault

Refs: #10774

a3p-integration/proposals/n:upgrade-next/priceFeedUpdate.test.js

@@ -19,6 +19,7 @@ import {
 } from '@agoric/synthetic-chain';
 import {
   getPriceFeedRoundId,
+  tryISTBalances,
   verifyPushedPrice,
 } from './test-lib/price-feed.js';
 
@@ -79,16 +80,19 @@ const createNewBid = async t => {
 };
 
 const openMarginalVault = async t => {
-  let user1IST = await getISTBalance(USER1ADDR);
+  const istBalanceBeforeVaultOpen = await getISTBalance(USER1ADDR, 'uist', 1);
   await bankSend(USER1ADDR, `20000000${ATOM_DENOM}`);
   const currentVaults = await agops.vaults('list', '--from', USER1ADDR);
 
   t.log('opening a vault');
   // @ts-expect-error bad typedef
   await openVault(USER1ADDR, 5, 10);
-  user1IST += 5;
-  const istBalanceAfterVaultOpen = await getISTBalance(USER1ADDR);
-  t.is(istBalanceAfterVaultOpen, user1IST);
+  const istBalanceAfterVaultOpen = await getISTBalance(USER1ADDR, 'uist', 1);
+  await tryISTBalances(
+    t,
+    istBalanceAfterVaultOpen,
+    istBalanceBeforeVaultOpen + 5_000_000, // in uist
+  );
 
   const activeVaultsAfter = await agops.vaults('list', '--from', USER1ADDR);
   t.log(currentVaults, activeVaultsAfter);

a3p-integration/proposals/n:upgrade-next/test-lib/price-feed.js

@@ -60,3 +60,32 @@ export const getPriceFeedRoundId = async brand => {
   console.log(latestRoundPath, latestRound);
   return Number(latestRound.roundId);
 };
+
+/**
+ * Copy from https://github.com/Agoric/agoric-sdk/blob/745f2a82cc94e246f98dd1bd69cb679b608a7170/a3p-integration/proposals/p%3Aupgrade-19/test-lib/psm-lib.js#L277
+ *
+ * Checking IST balances can be tricky because of the execution fee mentioned in
+ * https://github.com/Agoric/agoric-sdk/issues/6525. So we first check for
+ * equality, but if that fails we recheck against an assumption that a fee of
+ * the default "minFeeDebit" has been charged.
+ *
+ * @param {import('ava').ExecutionContext} t
+ * @param {number} actualBalance
+ * @param {number} expectedBalance
+ */
+export const tryISTBalances = async (t, actualBalance, expectedBalance) => {
+  const firstTry = await t.try(tt => {
+    tt.is(actualBalance, expectedBalance);
+  });
+  if (firstTry.passed) {
+    firstTry.commit();
+    return;
+  }
+
+  firstTry.discard();
+  t.log('tryISTBalances assuming no batched IST fee', ...firstTry.errors);
+  // See golang/cosmos/x/swingset/types/default-params.go
+  // and `ChargeBeans` in golang/cosmos/x/swingset/keeper/keeper.go.
+  const minFeeDebit = 200_000;
+  t.is(actualBalance + minFeeDebit, expectedBalance);
+};