add safe ERC20 helpers

test/SafeERC20.js

@@ -0,0 +1,27 @@
+import EVMThrow from './helpers/EVMThrow';
+
+require('chai')
+  .use(require('chai-as-promised'))
+  .should();
+
+const SafeERC20Helper = artifacts.require('./helpers/SafeERC20Helper.sol');
+
+contract('SafeERC20', function () {
+
+  beforeEach(async function () {
+    this.helper = await SafeERC20Helper.new();
+  });
+
+  it('should throw on failed transfer', async function () {
+    await this.helper.doFailingTransfer().should.be.rejectedWith(EVMThrow);
+  });
+
+  it('should throw on failed transferFrom', async function () {
+    await this.helper.doFailingTransferFrom().should.be.rejectedWith(EVMThrow);
+  });
+
+  it('should throw on failed approve', async function () {
+    await this.helper.doFailingApprove().should.be.rejectedWith(EVMThrow);
+  });
+
+});