Reorganize the repo structure (#2503)

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

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

@@ -0,0 +1,110 @@
+const { BN, constants, expectEvent, expectRevert } = require('@openzeppelin/test-helpers');
+const { ZERO_ADDRESS } = constants;
+
+const { expect } = require('chai');
+
+function shouldBehaveLikeERC20Burnable (owner, initialBalance, [burner]) {
+  describe('burn', function () {
+    describe('when the given amount is not greater than balance of the sender', function () {
+      context('for a zero amount', function () {
+        shouldBurn(new BN(0));
+      });
+
+      context('for a non-zero amount', function () {
+        shouldBurn(new BN(100));
+      });
+
+      function shouldBurn (amount) {
+        beforeEach(async function () {
+          ({ logs: this.logs } = await this.token.burn(amount, { from: owner }));
+        });
+
+        it('burns the requested amount', async function () {
+          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal(initialBalance.sub(amount));
+        });
+
+        it('emits a transfer event', async function () {
+          expectEvent.inLogs(this.logs, 'Transfer', {
+            from: owner,
+            to: ZERO_ADDRESS,
+            value: amount,
+          });
+        });
+      }
+    });
+
+    describe('when the given amount is greater than the balance of the sender', function () {
+      const amount = initialBalance.addn(1);
+
+      it('reverts', async function () {
+        await expectRevert(this.token.burn(amount, { from: owner }),
+          'ERC20: burn amount exceeds balance',
+        );
+      });
+    });
+  });
+
+  describe('burnFrom', function () {
+    describe('on success', function () {
+      context('for a zero amount', function () {
+        shouldBurnFrom(new BN(0));
+      });
+
+      context('for a non-zero amount', function () {
+        shouldBurnFrom(new BN(100));
+      });
+
+      function shouldBurnFrom (amount) {
+        const originalAllowance = amount.muln(3);
+
+        beforeEach(async function () {
+          await this.token.approve(burner, originalAllowance, { from: owner });
+          const { logs } = await this.token.burnFrom(owner, amount, { from: burner });
+          this.logs = logs;
+        });
+
+        it('burns the requested amount', async function () {
+          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal(initialBalance.sub(amount));
+        });
+
+        it('decrements allowance', async function () {
+          expect(await this.token.allowance(owner, burner)).to.be.bignumber.equal(originalAllowance.sub(amount));
+        });
+
+        it('emits a transfer event', async function () {
+          expectEvent.inLogs(this.logs, 'Transfer', {
+            from: owner,
+            to: ZERO_ADDRESS,
+            value: amount,
+          });
+        });
+      }
+    });
+
+    describe('when the given amount is greater than the balance of the sender', function () {
+      const amount = initialBalance.addn(1);
+
+      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',
+        );
+      });
+    });
+
+    describe('when the given amount is greater than the allowance', function () {
+      const allowance = new BN(100);
+
+      it('reverts', async function () {
+        await this.token.approve(burner, allowance, { from: owner });
+        await expectRevert(this.token.burnFrom(owner, allowance.addn(1), { from: burner }),
+          'ERC20: burn amount exceeds allowance',
+        );
+      });
+    });
+  });
+}
+
+module.exports = {
+  shouldBehaveLikeERC20Burnable,
+};