Fix ERC20._update (#3921)

Co-authored-by: Francisco <frangio.1@gmail.com>
Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>

test/token/ERC20/ERC20.test.js

@@ -250,7 +250,7 @@ contract('ERC20', function (accounts) {
     describe('for a non zero account', function () {
       it('rejects burning more than balance', async function () {
         await expectRevert(this.token.burn(
-          initialHolder, initialSupply.addn(1)), 'ERC20: burn amount exceeds balance',
+          initialHolder, initialSupply.addn(1)), 'ERC20: transfer amount exceeds balance',
         );
       });
 
@@ -287,6 +287,49 @@ contract('ERC20', function (accounts) {
     });
   });
 
+  describe('_update', function () {
+    const amount = new BN(1);
+
+    it('from is the zero address', async function () {
+      const balanceBefore = await this.token.balanceOf(initialHolder);
+      const totalSupply = await this.token.totalSupply();
+
+      expectEvent(
+        await this.token.update(ZERO_ADDRESS, initialHolder, amount),
+        'Transfer',
+        { from: ZERO_ADDRESS, to: initialHolder, value: amount },
+      );
+      expect(await this.token.totalSupply()).to.be.bignumber.equal(totalSupply.add(amount));
+      expect(await this.token.balanceOf(initialHolder)).to.be.bignumber.equal(balanceBefore.add(amount));
+    });
+
+    it('to is the zero address', async function () {
+      const balanceBefore = await this.token.balanceOf(initialHolder);
+      const totalSupply = await this.token.totalSupply();
+
+      expectEvent(
+        await this.token.update(initialHolder, ZERO_ADDRESS, amount),
+        'Transfer',
+        { from: initialHolder, to: ZERO_ADDRESS, value: amount },
+      );
+      expect(await this.token.totalSupply()).to.be.bignumber.equal(totalSupply.sub(amount));
+      expect(await this.token.balanceOf(initialHolder)).to.be.bignumber.equal(balanceBefore.sub(amount));
+    });
+
+    it('from and to are the zero address', async function () {
+      const totalSupply = await this.token.totalSupply();
+
+      await this.token.update(ZERO_ADDRESS, ZERO_ADDRESS, amount);
+
+      expect(await this.token.totalSupply()).to.be.bignumber.equal(totalSupply);
+      expectEvent(
+        await this.token.update(ZERO_ADDRESS, ZERO_ADDRESS, amount),
+        'Transfer',
+        { from: ZERO_ADDRESS, to: ZERO_ADDRESS, value: amount },
+      );
+    });
+  });
+
   describe('_transfer', function () {
     shouldBehaveLikeERC20Transfer('ERC20', initialHolder, recipient, initialSupply, function (from, to, amount) {
       return this.token.transferInternal(from, to, amount);

test/token/ERC20/extensions/ERC20Burnable.behavior.js

@@ -38,7 +38,7 @@ function shouldBehaveLikeERC20Burnable (owner, initialBalance, [burner]) {
 
       it('reverts', async function () {
         await expectRevert(this.token.burn(amount, { from: owner }),
-          'ERC20: burn amount exceeds balance',
+          'ERC20: transfer amount exceeds balance',
         );
       });
     });
@@ -86,7 +86,7 @@ function shouldBehaveLikeERC20Burnable (owner, initialBalance, [burner]) {
       it('reverts', async function () {
         await this.token.approve(burner, amount, { from: owner });
         await expectRevert(this.token.burnFrom(owner, amount, { from: burner }),
-          'ERC20: burn amount exceeds balance',
+          'ERC20: transfer amount exceeds balance',
         );
       });
     });

test/token/ERC20/extensions/ERC20FlashMint.test.js

@@ -82,7 +82,7 @@ contract('ERC20FlashMint', function (accounts) {
       const data = this.token.contract.methods.transfer(other, 10).encodeABI();
       await expectRevert(
         this.token.flashLoan(receiver.address, this.token.address, loanAmount, data),
-        'ERC20: burn amount exceeds balance',
+        'ERC20: transfer amount exceeds balance',
       );
     });
 

test/token/ERC20/extensions/ERC20Wrapper.test.js

@@ -105,7 +105,7 @@ contract('ERC20', function (accounts) {
     it('missing balance', async function () {
       await expectRevert(
         this.token.withdrawTo(initialHolder, MAX_UINT256, { from: initialHolder }),
-        'ERC20: burn amount exceeds balance',
+        'ERC20: transfer amount exceeds balance',
       );
     });