3 files changed, 13 insertions, 10 deletions
diff --git a/packages/order-utils/src/rate_utils.ts b/packages/order-utils/src/rate_utils.ts
index 212431e0c..72d11584a 100644
--- a/packages/order-utils/src/rate_utils.ts
+++ b/packages/order-utils/src/rate_utils.ts
@@ -1,6 +1,7 @@
 import { schemas } from '@0xproject/json-schemas';
 import { SignedOrder } from '@0xproject/types';
 import { BigNumber } from '@0xproject/utils';
+import * as _ from 'lodash';
 
 import { assert } from './assert';
 import { constants } from './constants';
@@ -12,12 +13,16 @@ export const rateUtils = {
      * @param   signedOrder     An object that conforms to the signedOrder interface
      * @param   feeRate         The market rate of ZRX denominated in takerAssetAmount
      *                          (ex. feeRate is 0.1 takerAsset/ZRX if it takes 1 unit of takerAsset to buy 10 ZRX)
+     *                          Defaults to 0
      * @return  The rate (takerAsset/makerAsset) of the order adjusted for fees
      */
-    getFeeAdjustedRateOfOrder(signedOrder: SignedOrder, feeRate: BigNumber): BigNumber {
+    getFeeAdjustedRateOfOrder(signedOrder: SignedOrder, feeRate: BigNumber = constants.ZERO_AMOUNT): BigNumber {
         assert.doesConformToSchema('signedOrder', signedOrder, schemas.signedOrderSchema);
         assert.isBigNumber('feeRate', feeRate);
-        assert.assert(feeRate.greaterThan(constants.ZERO_AMOUNT), `Expected feeRate: ${feeRate} to be greater than 0`);
+        assert.assert(
+            feeRate.gte(constants.ZERO_AMOUNT),
+            `Expected feeRate: ${feeRate} to be greater than or equal to 0`,
+        );
         const takerAssetAmountNeededToPayForFees = signedOrder.takerFee.mul(feeRate);
         const totalTakerAssetAmount = takerAssetAmountNeededToPayForFees.plus(signedOrder.takerAssetAmount);
         const rate = totalTakerAssetAmount.div(signedOrder.makerAssetAmount);
diff --git a/packages/order-utils/src/sorting_utils.ts b/packages/order-utils/src/sorting_utils.ts
index 2acd8180f..8424060fc 100644
--- a/packages/order-utils/src/sorting_utils.ts
+++ b/packages/order-utils/src/sorting_utils.ts
@@ -15,9 +15,13 @@ export const sortingUtils = {
      *                              the makerAsset and WETH as the takerAsset.
      * @param   feeRate             The market rate of ZRX denominated in takerAssetAmount
      *                              (ex. feeRate is 0.1 takerAsset/ZRX if it takes 1 unit of takerAsset to buy 10 ZRX)
+     *                              Defaults to 0
      * @return  The input orders sorted by rate in ascending order
      */
-    sortOrdersByFeeAdjustedRate(signedOrders: SignedOrder[], feeRate: BigNumber): SignedOrder[] {
+    sortOrdersByFeeAdjustedRate(
+        signedOrders: SignedOrder[],
+        feeRate: BigNumber = constants.ZERO_AMOUNT,
+    ): SignedOrder[] {
         assert.doesConformToSchema('signedOrders', signedOrders, schemas.signedOrdersSchema);
         assert.isBigNumber('feeRate', feeRate);
         const rateCalculator = (signedOrder: SignedOrder) => rateUtils.getFeeAdjustedRateOfOrder(signedOrder, feeRate);
diff --git a/packages/order-utils/test/rate_utils_test.ts b/packages/order-utils/test/rate_utils_test.ts
index 2f321a7db..167a40465 100644
--- a/packages/order-utils/test/rate_utils_test.ts
+++ b/packages/order-utils/test/rate_utils_test.ts
@@ -17,16 +17,10 @@ describe('rateUtils', () => {
         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',
+                'Expected feeRate: -1 to be greater than or equal to 0',
             );
         });
         it('correctly calculates fee adjusted rate', async () => {