Migration to 0x coverage tools

.gitignore

@@ -40,3 +40,6 @@ build/
 
 # IntelliJ IDE
 .idea
+
+# 0x artifacts
+.0x-artifacts/*

contracts/mocks/ERC20NoReturnMock.sol

@@ -0,0 +1,30 @@
+pragma solidity ^0.5.2;
+
+contract ERC20NoReturnMock {
+    mapping (address => uint256) private _allowances;
+
+    // IERC20's functions are not pure, but these mock implementations are: to prevent Solidity from issuing warnings,
+    // we write to a dummy state variable.
+    uint256 private _dummy;
+
+    function transfer(address, uint256) public {
+        _dummy = 0;
+    }
+
+    function transferFrom(address, address, uint256) public {
+        _dummy = 0;
+    }
+
+    function approve(address, uint256) public {
+        _dummy = 0;
+    }
+
+    function setAllowance(uint256 allowance_) public {
+        _allowances[msg.sender] = allowance_;
+    }
+
+    function allowance(address owner, address) public view returns (uint256) {
+        return _allowances[owner];
+    }
+}
+

contracts/mocks/ERC20ReturnFalseMock.sol

@@ -0,0 +1,29 @@
+pragma solidity ^0.5.2;
+
+contract ERC20ReturnFalseMock {
+    uint256 private _allowance;
+
+    // IERC20's functions are not pure, but these mock implementations are: to prevent Solidity from issuing warnings,
+    // we write to a dummy state variable.
+    uint256 private _dummy;
+
+    function transfer(address, uint256) public returns (bool) {
+        _dummy = 0;
+        return false;
+    }
+
+    function transferFrom(address, address, uint256) public returns (bool) {
+        _dummy = 0;
+        return false;
+    }
+
+    function approve(address, uint256) public returns (bool) {
+        _dummy = 0;
+        return false;
+    }
+
+    function allowance(address, address) public view returns (uint256) {
+        require(_dummy == 0);
+        return 0;
+    }
+}

contracts/mocks/ERC20ReturnTrueMock.sol

@@ -0,0 +1,33 @@
+pragma solidity ^0.5.2;
+
+contract ERC20ReturnTrueMock {
+    mapping (address => uint256) private _allowances;
+
+    // IERC20's functions are not pure, but these mock implementations are: to prevent Solidity from issuing warnings,
+    // we write to a dummy state variable.
+    uint256 private _dummy;
+
+    function transfer(address, uint256) public returns (bool) {
+        _dummy = 0;
+        return true;
+    }
+
+    function transferFrom(address, address, uint256) public returns (bool) {
+        _dummy = 0;
+        return true;
+    }
+
+    function approve(address, uint256) public returns (bool) {
+        _dummy = 0;
+        return true;
+    }
+
+    function setAllowance(uint256 allowance_) public {
+        _allowances[msg.sender] = allowance_;
+    }
+
+    function allowance(address owner, address) public view returns (uint256) {
+        return _allowances[owner];
+    }
+}
+

contracts/mocks/SafeERC20Wrapper.sol

@@ -0,0 +1,43 @@
+pragma solidity ^0.5.2;
+
+import "../token/ERC20/IERC20.sol";
+import "../token/ERC20/SafeERC20.sol";
+import "./ERC20ReturnTrueMock.sol";
+
+contract SafeERC20Wrapper {
+    using SafeERC20 for IERC20;
+
+    IERC20 private _token;
+
+    constructor (IERC20 token) public {
+        _token = token;
+    }
+
+    function transfer() public {
+        _token.safeTransfer(address(0), 0);
+    }
+
+    function transferFrom() public {
+        _token.safeTransferFrom(address(0), address(0), 0);
+    }
+
+    function approve(uint256 amount) public {
+        _token.safeApprove(address(0), amount);
+    }
+
+    function increaseAllowance(uint256 amount) public {
+        _token.safeIncreaseAllowance(address(0), amount);
+    }
+
+    function decreaseAllowance(uint256 amount) public {
+        _token.safeDecreaseAllowance(address(0), amount);
+    }
+
+    function setAllowance(uint256 allowance_) public {
+        ERC20ReturnTrueMock(address(_token)).setAllowance(allowance_);
+    }
+
+    function allowance() public view returns (uint256) {
+        return _token.allowance(address(0), address(0));
+    }
+}