fix potential flake caused by checking IST balances (#10783)

closes: #10774

## Description

Due to the execution fee charged in batches is difficult to guess/reproduce, we introduced the method `tryISTBalances` instead of a regular balance check done using `t.is`. This PR is an effort to migrate existing IST balance checks using `t.is` (or alike) to use `tryISTBalances`. I believe this will prevent potential flakes in our `a3p-integration` tests in the future.

### Security Considerations

We are only changing the way we compare numbers in our tests. No security concern here.

### Scaling Considerations

By avoiding flakes we'll improve the scaling in the long run.

### Documentation Considerations

None.

### Testing Considerations

Integration tests should be forced in CI and all tests should pass.

### Upgrade Considerations

We are improving the way we test our upgrades. No other concern here as well.

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);
+};

a3p-integration/proposals/p:upgrade-19/test-lib/mintHolder-helpers.js

@@ -8,7 +8,10 @@ import {
 } from '@agoric/synthetic-chain';
 import { makeVstorageKit, retryUntilCondition } from '@agoric/client-utils';
 import { readFile, writeFile } from 'node:fs/promises';
-import { psmSwap, snapshotAgoricNames } from './psm-lib.js';
+import { psmSwap, snapshotAgoricNames, tryISTBalances } from './psm-lib.js';
+
+/** @type {(x: number) => number} */
+const scale6 = x => x * 1_000_000;
 
 /**
  * @param {string} fileName base file name without .tjs extension
@@ -89,6 +92,13 @@ export const mintPayment = async (t, address, assetList, value) => {
   }
 };
 
+/**
+ *
+ * @param {import('ava').ExecutionContext} t
+ * @param {string} address
+ * @param {Array<{ label: string, denom: string, mintHolderVat: string}>} assetList
+ * @param {number} want in IST
+ */
 export const swap = async (t, address, assetList, want) => {
   for (const asset of assetList) {
     const { label, denom } = asset;
@@ -100,7 +110,7 @@ export const swap = async (t, address, assetList, want) => {
 
     const pair = `IST.${label}`;
 
-    const istBalanceBefore = await getISTBalance(address, 'uist');
+    const istBalanceBefore = await getISTBalance(address, 'uist', 1); // we want uist not IST
     const anchorBalanceBefore = await getISTBalance(address, denom);
 
     const psmSwapIo = {
@@ -116,10 +126,14 @@ export const swap = async (t, address, assetList, want) => {
       psmSwapIo,
     );
 
-    const istBalanceAfter = await getISTBalance(address, 'uist');
+    const istBalanceAfter = await getISTBalance(address, 'uist', 1); // we want uist not IST
     const anchorBalanceAfter = await getISTBalance(address, denom);
 
-    t.is(istBalanceAfter, istBalanceBefore + want);
+    await tryISTBalances(
+      t,
+      istBalanceAfter,
+      istBalanceBefore + scale6(want), // scale "want" to uist
+    );
     t.is(anchorBalanceAfter, anchorBalanceBefore - want);
   }
 };