Add transaction hash utils

packages/order-utils/test/transaction_hash_test.ts

@@ -0,0 +1,56 @@
+import { ZeroExTransaction } from '@0x/types';
+import { BigNumber } from '@0x/utils';
+import * as chai from 'chai';
+import 'mocha';
+
+import { transactionHashUtils } from '../src';
+
+import { constants } from '../src/constants';
+
+import { chaiSetup } from './utils/chai_setup';
+
+chaiSetup.configure();
+const expect = chai.expect;
+
+describe.only('0x transaction hashing', () => {
+    describe('#getTransactionHashHex', () => {
+        const expectedTransactionHash = '0x82c9bb2dcac4f868ec7a15c20ff6175cfc384c20ae6a872aa0342a840f108c2b';
+        const fakeVerifyingContractAddress = '0x5e72914535f202659083db3a02c984188fa26e9f';
+        const transaction: ZeroExTransaction = {
+            verifyingContractAddress: fakeVerifyingContractAddress,
+            signerAddress: constants.NULL_ADDRESS,
+            salt: new BigNumber(0),
+            data: constants.NULL_BYTES,
+        };
+        it('calculates the transaction hash', async () => {
+            const transactionHash = transactionHashUtils.getTransactionHashHex(transaction);
+            expect(transactionHash).to.be.equal(expectedTransactionHash);
+        });
+        it('calculates the transaction hash if amounts are strings', async () => {
+            // It's common for developers using javascript to provide the amounts
+            // as strings. Since we eventually toString() the BigNumber
+            // before encoding we should result in the same orderHash in this scenario
+            // tslint:disable-next-line:no-unnecessary-type-assertion
+            const transactionHash = transactionHashUtils.getTransactionHashHex({
+                ...transaction,
+                salt: '0',
+            } as any);
+            expect(transactionHash).to.be.equal(expectedTransactionHash);
+        });
+    });
+    describe('#isValidTransactionHash', () => {
+        it('returns false if the value is not a hex string', () => {
+            const isValid = transactionHashUtils.isValidTransactionHash('not a hex');
+            expect(isValid).to.be.false();
+        });
+        it('returns false if the length is wrong', () => {
+            const isValid = transactionHashUtils.isValidTransactionHash('0xdeadbeef');
+            expect(isValid).to.be.false();
+        });
+        it('returns true if order hash is correct', () => {
+            const orderHashLength = 65;
+            const isValid = transactionHashUtils.isValidTransactionHash(`0x${Array(orderHashLength).join('0')}`);
+            expect(isValid).to.be.true();
+        });
+    });
+});