3 files changed, 99 insertions, 1 deletions
diff --git a/packages/instant/package.json b/packages/instant/package.json
index befedfc17..b991d0e05 100644
--- a/packages/instant/package.json
+++ b/packages/instant/package.json
@@ -63,6 +63,7 @@
         "@0xproject/tslint-config": "^1.0.8",
         "@types/enzyme": "^3.1.14",
         "@types/enzyme-adapter-react-16": "^1.0.3",
+        "@types/jest": "^23.3.5",
         "@types/lodash": "^4.14.116",
         "@types/node": "*",
         "@types/react": "^16.4.16",
diff --git a/packages/instant/src/util/format.ts b/packages/instant/src/util/format.ts
index de7eb62e6..b62c968fb 100644
--- a/packages/instant/src/util/format.ts
+++ b/packages/instant/src/util/format.ts
@@ -40,6 +40,6 @@ export const format = {
         if (_.isUndefined(ethUnitAmount) || _.isUndefined(ethUsdPrice)) {
             return defaultText;
         }
-        return `$${ethUnitAmount.mul(ethUsdPrice).round(decimalPlaces)}`;
+        return `$${ethUnitAmount.mul(ethUsdPrice).toFixed(decimalPlaces)}`;
     },
 };
diff --git a/packages/instant/test/util/format.test.ts b/packages/instant/test/util/format.test.ts
new file mode 100644
index 000000000..073b86b19
--- /dev/null
+++ b/packages/instant/test/util/format.test.ts
@@ -0,0 +1,97 @@
+import { BigNumber } from '@0xproject/utils';
+import { Web3Wrapper } from '@0xproject/web3-wrapper';
+
+import { ethDecimals } from '../../src/constants';
+import { format } from '../../src/util/format';
+
+const BIG_NUMBER_ONE = new BigNumber(1);
+const BIG_NUMBER_DECIMAL = new BigNumber(0.432414);
+const BIG_NUMBER_IRRATIONAL = new BigNumber(5.3014059295032);
+const ONE_ETH_IN_BASE_UNITS = Web3Wrapper.toBaseUnitAmount(BIG_NUMBER_ONE, ethDecimals);
+const DECIMAL_ETH_IN_BASE_UNITS = Web3Wrapper.toBaseUnitAmount(BIG_NUMBER_DECIMAL, ethDecimals);
+const IRRATIONAL_ETH_IN_BASE_UNITS = Web3Wrapper.toBaseUnitAmount(BIG_NUMBER_IRRATIONAL, ethDecimals);
+const BIG_NUMBER_FAKE_ETH_USD_PRICE = new BigNumber(2.534);
+
+describe('format', () => {
+    describe('ethBaseAmount', () => {
+        it('converts 1 ETH in base units to the string `1 ETH`', () => {
+            expect(format.ethBaseAmount(ONE_ETH_IN_BASE_UNITS)).toBe('1 ETH');
+        });
+        it('converts .432414 ETH in base units to the string `.4324 ETH`', () => {
+            expect(format.ethBaseAmount(DECIMAL_ETH_IN_BASE_UNITS)).toBe('0.4324 ETH');
+        });
+        it('converts 5.3014059295032 ETH in base units to the string `5.3014 ETH`', () => {
+            expect(format.ethBaseAmount(IRRATIONAL_ETH_IN_BASE_UNITS)).toBe('5.3014 ETH');
+        });
+        it('returns defaultText param when ethBaseAmount is not defined', () => {
+            const defaultText = 'defaultText';
+            expect(format.ethBaseAmount(undefined, 4, defaultText)).toBe(defaultText);
+        });
+        it('it allows for configurable decimal places', () => {
+            expect(format.ethBaseAmount(DECIMAL_ETH_IN_BASE_UNITS, 2)).toBe('0.43 ETH');
+        });
+    });
+    describe('ethUnitAmount', () => {
+        it('converts BigNumber(1) to the string `1 ETH`', () => {
+            expect(format.ethUnitAmount(BIG_NUMBER_ONE)).toBe('1 ETH');
+        });
+        it('converts BigNumer(.432414) to the string `.4324 ETH`', () => {
+            expect(format.ethUnitAmount(BIG_NUMBER_DECIMAL)).toBe('0.4324 ETH');
+        });
+        it('converts BigNumber(5.3014059295032) to the string `5.3014 ETH`', () => {
+            expect(format.ethUnitAmount(BIG_NUMBER_IRRATIONAL)).toBe('5.3014 ETH');
+        });
+        it('returns defaultText param when ethUnitAmount is not defined', () => {
+            const defaultText = 'defaultText';
+            expect(format.ethUnitAmount(undefined, 4, defaultText)).toBe(defaultText);
+            expect(format.ethUnitAmount(BIG_NUMBER_ONE, 4, defaultText)).toBe('1 ETH');
+        });
+        it('it allows for configurable decimal places', () => {
+            expect(format.ethUnitAmount(BIG_NUMBER_DECIMAL, 2)).toBe('0.43 ETH');
+        });
+    });
+    describe('ethBaseAmountInUsd', () => {
+        it('correctly formats 1 ETH to usd according to some price', () => {
+            expect(format.ethBaseAmountInUsd(ONE_ETH_IN_BASE_UNITS, BIG_NUMBER_FAKE_ETH_USD_PRICE)).toBe('$2.53');
+        });
+        it('correctly formats .432414 ETH to usd according to some price', () => {
+            expect(format.ethBaseAmountInUsd(DECIMAL_ETH_IN_BASE_UNITS, BIG_NUMBER_FAKE_ETH_USD_PRICE)).toBe('$1.10');
+        });
+        it('correctly formats 5.3014059295032 ETH to usd according to some price', () => {
+            expect(format.ethBaseAmountInUsd(IRRATIONAL_ETH_IN_BASE_UNITS, BIG_NUMBER_FAKE_ETH_USD_PRICE)).toBe(
+                '$13.43',
+            );
+        });
+        it('returns defaultText param when ethBaseAmountInUsd or ethUsdPrice is not defined', () => {
+            const defaultText = 'defaultText';
+            expect(format.ethBaseAmountInUsd(undefined, undefined, 2, defaultText)).toBe(defaultText);
+            expect(format.ethBaseAmountInUsd(BIG_NUMBER_ONE, undefined, 2, defaultText)).toBe(defaultText);
+            expect(format.ethBaseAmountInUsd(undefined, BIG_NUMBER_ONE, 2, defaultText)).toBe(defaultText);
+        });
+        it('it allows for configurable decimal places', () => {
+            expect(format.ethBaseAmountInUsd(DECIMAL_ETH_IN_BASE_UNITS, BIG_NUMBER_FAKE_ETH_USD_PRICE, 4)).toBe(
+                '$1.0957',
+            );
+        });
+    });
+    describe('ethUnitAmountInUsd', () => {
+        it('correctly formats 1 ETH to usd according to some price', () => {
+            expect(format.ethUnitAmountInUsd(BIG_NUMBER_ONE, BIG_NUMBER_FAKE_ETH_USD_PRICE)).toBe('$2.53');
+        });
+        it('correctly formats .432414 ETH to usd according to some price', () => {
+            expect(format.ethUnitAmountInUsd(BIG_NUMBER_DECIMAL, BIG_NUMBER_FAKE_ETH_USD_PRICE)).toBe('$1.10');
+        });
+        it('correctly formats 5.3014059295032 ETH to usd according to some price', () => {
+            expect(format.ethUnitAmountInUsd(BIG_NUMBER_IRRATIONAL, BIG_NUMBER_FAKE_ETH_USD_PRICE)).toBe('$13.43');
+        });
+        it('returns defaultText param when ethUnitAmountInUsd or ethUsdPrice is not defined', () => {
+            const defaultText = 'defaultText';
+            expect(format.ethUnitAmountInUsd(undefined, undefined, 2, defaultText)).toBe(defaultText);
+            expect(format.ethUnitAmountInUsd(BIG_NUMBER_ONE, undefined, 2, defaultText)).toBe(defaultText);
+            expect(format.ethUnitAmountInUsd(undefined, BIG_NUMBER_ONE, 2, defaultText)).toBe(defaultText);
+        });
+        it('it allows for configurable decimal places', () => {
+            expect(format.ethUnitAmountInUsd(BIG_NUMBER_DECIMAL, BIG_NUMBER_FAKE_ETH_USD_PRICE, 4)).toBe('$1.0957');
+        });
+    });
+});