Update docs

test/token/ERC721/extensions/ERC721Burnable.test.js

@@ -0,0 +1,80 @@
+const { BN, constants, expectEvent, expectRevert } = require('@openzeppelin/test-helpers');
+const { ZERO_ADDRESS } = constants;
+
+const { expect } = require('chai');
+
+const ERC721BurnableMock = artifacts.require('ERC721BurnableMock');
+
+contract('ERC721Burnable', function (accounts) {
+  const [owner, approved] = accounts;
+
+  const firstTokenId = new BN(1);
+  const secondTokenId = new BN(2);
+  const unknownTokenId = new BN(3);
+
+  const name = 'Non Fungible Token';
+  const symbol = 'NFT';
+
+  beforeEach(async function () {
+    this.token = await ERC721BurnableMock.new(name, symbol);
+  });
+
+  describe('like a burnable ERC721', function () {
+    beforeEach(async function () {
+      await this.token.mint(owner, firstTokenId);
+      await this.token.mint(owner, secondTokenId);
+    });
+
+    describe('burn', function () {
+      const tokenId = firstTokenId;
+      let logs = null;
+
+      describe('when successful', function () {
+        beforeEach(async function () {
+          const result = await this.token.burn(tokenId, { from: owner });
+          logs = result.logs;
+        });
+
+        it('burns the given token ID and adjusts the balance of the owner', async function () {
+          await expectRevert(
+            this.token.ownerOf(tokenId),
+            'ERC721: owner query for nonexistent token',
+          );
+          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('1');
+        });
+
+        it('emits a burn event', async function () {
+          expectEvent.inLogs(logs, 'Transfer', {
+            from: owner,
+            to: ZERO_ADDRESS,
+            tokenId: tokenId,
+          });
+        });
+      });
+
+      describe('when there is a previous approval burned', function () {
+        beforeEach(async function () {
+          await this.token.approve(approved, tokenId, { from: owner });
+          const result = await this.token.burn(tokenId, { from: owner });
+          logs = result.logs;
+        });
+
+        context('getApproved', function () {
+          it('reverts', async function () {
+            await expectRevert(
+              this.token.getApproved(tokenId), 'ERC721: approved query for nonexistent token',
+            );
+          });
+        });
+      });
+
+      describe('when the given token ID was not tracked by this contract', function () {
+        it('reverts', async function () {
+          await expectRevert(
+            this.token.burn(unknownTokenId, { from: owner }), 'ERC721: operator query for nonexistent token',
+          );
+        });
+      });
+    });
+  });
+});