Reorganize the repo structure (#2503)

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

test/utils/introspection/ERC165Storage.test.js

@@ -0,0 +1,25 @@
+const { expectRevert } = require('@openzeppelin/test-helpers');
+
+const { shouldSupportInterfaces } = require('./SupportsInterface.behavior');
+
+const ERC165Mock = artifacts.require('ERC165StorageMock');
+
+contract('ERC165Storage', function (accounts) {
+  beforeEach(async function () {
+    this.mock = await ERC165Mock.new();
+  });
+
+  it('register interface', async function () {
+    expect(await this.mock.supportsInterface('0x00000001')).to.be.equal(false);
+    await this.mock.registerInterface('0x00000001');
+    expect(await this.mock.supportsInterface('0x00000001')).to.be.equal(true);
+  });
+
+  it('does not allow 0xffffffff', async function () {
+    await expectRevert(this.mock.registerInterface('0xffffffff'), 'ERC165: invalid interface id');
+  });
+
+  shouldSupportInterfaces([
+    'ERC165',
+  ]);
+});