fix!: improve error message when a purse is overdrawn (#3811)

* fix!: improve error message when a purse is overdrawn

Author: katelynsills

packages/ERTP/src/paymentLedger.js

@@ -291,7 +291,12 @@ export const makePaymentLedger = (
    */
   const withdraw = (currentBalance, updatePurseBalance, amount) => {
     amount = coerce(amount);
+    assert(
+      AmountMath.isGTE(currentBalance, amount),
+      X`Withdrawal of ${amount} failed because the purse only contained ${currentBalance}`,
+    );
     const newPurseBalance = subtract(currentBalance, amount);
+
     const payment = makePayment(allegedName, brand);
     try {
       // COMMIT POINT

packages/ERTP/test/unitTests/test-issuerObj.js

@@ -129,6 +129,22 @@ test('issuer.makeEmptyPurse', async t => {
     .then(checkWithdrawal);
 });
 
+test('purse.withdraw overdrawn', async t => {
+  t.plan(1);
+  const { issuer, mint, brand } = makeIssuerKit('fungible');
+  const purse = issuer.makeEmptyPurse();
+  const purseBalance = AmountMath.make(brand, 103980n);
+  const payment = mint.mintPayment(purseBalance);
+  purse.deposit(payment);
+
+  const tooMuch = AmountMath.make(brand, 103981n);
+
+  t.throws(() => purse.withdraw(tooMuch), {
+    message:
+      'Withdrawal of {"brand":"[Alleged: fungible brand]","value":"[103981n]"} failed because the purse only contained {"brand":"[Alleged: fungible brand]","value":"[103980n]"}',
+  });
+});
+
 test('purse.deposit', async t => {
   t.plan(7);
   const { issuer, mint, brand } = makeIssuerKit('fungible');