add missing mocks

contracts/mocks/ERC20PresetMinterPauserMock.sol

+pragma solidity ^0.6.0;
+
+import '../presets/ERC20PresetMinterPauser.sol';
+
+contract ERC20PresetMinterPauserMock is ERC20PresetMinterPauser {
+    constructor (string memory name, string memory symbol) public payable ERC20PresetMinterPauser(name, symbol) {
+    }
+}

contracts/mocks/ERC721PresetMinterPauserAutoIdMock.sol

+pragma solidity ^0.6.0;
+
+import '../presets/ERC721PresetMinterPauserAutoId.sol';
+
+contract ERC721PresetMinterPauserAutoIdMock is ERC721PresetMinterPauserAutoId {
+    constructor (string memory name, string memory symbol, string memory baseURI) public payable ERC721PresetMinterPauserAutoId(name, symbol, baseURI) {
+    }
+}

contracts/mocks/EscrowMock.sol

+pragma solidity ^0.6.0;
+
+import '../payment/escrow/Escrow.sol';
+
+contract EscrowMock is Escrow {
+}

contracts/mocks/PaymentSplitterMock.sol

+pragma solidity ^0.6.0;
+
+import '../payment/PaymentSplitter.sol';
+
+contract PaymentSplitterMock is PaymentSplitter {
+    constructor (address[] memory payees, uint256[] memory shares) public payable PaymentSplitter(payees, shares) {
+    }
+}

contracts/mocks/RefundEscrowMock.sol

+pragma solidity ^0.6.0;
+
+import '../payment/escrow/RefundEscrow.sol';
+
+contract RefundEscrowMock is RefundEscrow {
+    constructor (address payable beneficiary) public payable RefundEscrow(beneficiary) {
+    }
+}

test/payment/PaymentSplitter.test.js

@@ -5,7 +5,7 @@ const { ZERO_ADDRESS } = constants;
 
 const { expect } = require('chai');
 
-const PaymentSplitter = contract.fromArtifact('PaymentSplitter');
+const PaymentSplitter = contract.fromArtifact('PaymentSplitterMock');
 
 describe('PaymentSplitter', function () {
   const [ owner, payee1, payee2, payee3, nonpayee1, payer1 ] = accounts;

test/payment/escrow/Escrow.test.js

@@ -3,7 +3,7 @@ const { accounts, contract } = require('@openzeppelin/test-environment');
 require('@openzeppelin/test-helpers');
 const { shouldBehaveLikeEscrow } = require('./Escrow.behavior');
 
-const Escrow = contract.fromArtifact('Escrow');
+const Escrow = contract.fromArtifact('EscrowMock');
 
 describe('Escrow', function () {
   const [ owner, ...otherAccounts ] = accounts;

test/payment/escrow/RefundEscrow.test.js

@@ -5,7 +5,7 @@ const { ZERO_ADDRESS } = constants;
 
 const { expect } = require('chai');
 
-const RefundEscrow = contract.fromArtifact('RefundEscrow');
+const RefundEscrow = contract.fromArtifact('RefundEscrowMock');
 
 describe('RefundEscrow', function () {
   const [ owner, beneficiary, refundee1, refundee2 ] = accounts;

test/presets/ERC20PresetMinterPauser.test.js

@@ -5,7 +5,7 @@ const { ZERO_ADDRESS } = constants;
 
 const { expect } = require('chai');
 
-const ERC20PresetMinterPauser = contract.fromArtifact('ERC20PresetMinterPauser');
+const ERC20PresetMinterPauser = contract.fromArtifact('ERC20PresetMinterPauserMock');
 
 describe('ERC20PresetMinterPauser', function () {
   const [ deployer, other ] = accounts;

test/presets/ERC721PresetMinterPauserAutoId.js

@@ -5,7 +5,7 @@ const { ZERO_ADDRESS } = constants;
 
 const { expect } = require('chai');
 
-const ERC721PresetMinterPauserAutoId = contract.fromArtifact('ERC721PresetMinterPauserAutoId');
+const ERC721PresetMinterPauserAutoId = contract.fromArtifact('ERC721PresetMinterPauserAutoIdMock');
 
 describe('ERC721PresetMinterPauserAutoId', function () {
   const [ deployer, other ] = accounts;

test/token/ERC20/TokenTimelock.test.js

@@ -5,7 +5,7 @@ const { BN, expectRevert, time } = require('@openzeppelin/test-helpers');
 const { expect } = require('chai');
 
 const ERC20Mock = contract.fromArtifact('ERC20Mock');
-const TokenTimelock = contract.fromArtifact('TokenTimelock');
+const TokenTimelock = contract.fromArtifact('TokenTimelockMock');
 
 describe('TokenTimelock', function () {
   const [ beneficiary ] = accounts;