Add bytes32 to bytes32 enumerable map (#3192)

* feat(enumerablemap): add bytes32 to bytes32 map

* chore(changelog): edit CHANGELOG

* feat(enumerable map): edit struct visibility

test/utils/structs/EnumerableMap.test.js

@@ -0,0 +1,58 @@
+const { BN, constants } = require('@openzeppelin/test-helpers');
+
+const AddressToUintMapMock = artifacts.require('AddressToUintMapMock');
+const UintToAddressMapMock = artifacts.require('UintToAddressMapMock');
+const Bytes32ToBytes32MapMock = artifacts.require('Bytes32ToBytes32MapMock');
+
+const { shouldBehaveLikeMap } = require('./EnumerableMap.behavior');
+
+contract('EnumerableMap', function (accounts) {
+  const [ accountA, accountB, accountC ] = accounts;
+
+  const keyA = new BN('7891');
+  const keyB = new BN('451');
+  const keyC = new BN('9592328');
+
+  const bytesA = '0xdeadbeef'.padEnd(66, '0');
+  const bytesB = '0x0123456789'.padEnd(66, '0');
+  const bytesC = '0x42424242'.padEnd(66, '0');
+
+  // AddressToUintMap
+  describe('AddressToUintMap', function () {
+    beforeEach(async function () {
+      this.map = await AddressToUintMapMock.new();
+    });
+
+    shouldBehaveLikeMap(
+      [accountA, accountB, accountC],
+      [keyA, keyB, keyC],
+      new BN('0'),
+    );
+  });
+
+  // UintToAddressMap
+  describe('UintToAddressMap', function () {
+    beforeEach(async function () {
+      this.map = await UintToAddressMapMock.new();
+    });
+
+    shouldBehaveLikeMap(
+      [keyA, keyB, keyC],
+      [accountA, accountB, accountC],
+      constants.ZERO_ADDRESS,
+    );
+  });
+
+  // Bytes32ToBytes32Map
+  describe('Bytes32ToBytes32Map', function () {
+    beforeEach(async function () {
+      this.map = await Bytes32ToBytes32MapMock.new();
+    });
+
+    shouldBehaveLikeMap(
+      [keyA, keyB, keyC].map(k => ('0x' + k.toString(16)).padEnd(66, '0')),
+      [bytesA, bytesB, bytesC],
+      constants.ZERO_BYTES32,
+    );
+  });
+});