Add tests for rateUtils

packages/order-utils/test/rate_utils_test.ts

@@ -0,0 +1,55 @@
+import { BigNumber } from '@0xproject/utils';
+import * as chai from 'chai';
+import 'mocha';
+
+import { constants, rateUtils } from '../src';
+
+import { chaiSetup } from './utils/chai_setup';
+import { testOrderFactory } from './utils/test_order_factory';
+
+chaiSetup.configure();
+const expect = chai.expect;
+
+describe('rateUtils', () => {
+    const testOrder = testOrderFactory.generateTestSignedOrder({
+        makerAssetAmount: new BigNumber(100),
+        takerAssetAmount: new BigNumber(100),
+        takerFee: new BigNumber(20),
+    });
+    describe('#getFeeAdjustedRateOfOrder', () => {
+        it('throws when feeRate is zero', async () => {
+            const feeRate = constants.ZERO_AMOUNT;
+            expect(() => rateUtils.getFeeAdjustedRateOfOrder(testOrder, feeRate)).to.throw(
+                'Expected feeRate: 0 to be greater than 0',
+            );
+        });
+        it('throws when feeRate is less than zero', async () => {
+            const feeRate = new BigNumber(-1);
+            expect(() => rateUtils.getFeeAdjustedRateOfOrder(testOrder, feeRate)).to.throw(
+                'Expected feeRate: -1 to be greater than 0',
+            );
+        });
+        it('correctly calculates fee adjusted rate', async () => {
+            const feeRate = new BigNumber(2); // ZRX costs 2 units of takerAsset per 1 unit of ZRX
+            const feeAdjustedRate = rateUtils.getFeeAdjustedRateOfOrder(testOrder, feeRate);
+            // the order actually takes 100 + (2 * 20) takerAsset units to fill 100 units of makerAsset
+            expect(feeAdjustedRate).to.bignumber.equal(new BigNumber(1.4));
+        });
+    });
+    describe('#getFeeAdjustedRateOfFeeOrder', () => {
+        it('throws when takerFee exceeds makerAssetAmount', async () => {
+            const badOrder = testOrderFactory.generateTestSignedOrder({
+                makerAssetAmount: new BigNumber(100),
+                takerFee: new BigNumber(101),
+            });
+            expect(() => rateUtils.getFeeAdjustedRateOfFeeOrder(badOrder)).to.throw(
+                'Expected takerFee: "101" to be less than makerAssetAmount: "100"',
+            );
+        });
+        it('correctly calculates fee adjusted rate', async () => {
+            const feeAdjustedRate = rateUtils.getFeeAdjustedRateOfFeeOrder(testOrder);
+            // the order actually takes 100 takerAsset units to fill (100 - 20) units of makerAsset
+            expect(feeAdjustedRate).to.bignumber.equal(new BigNumber(1.25));
+        });
+    });
+});