Merge pull request #2387 from 0xProject/feature/fuzz/staking-rewards

`@0x/contracts-integrations`: Staking rewards fuzz test

contracts/test-utils/package.json

@@ -65,6 +65,7 @@
         "chai": "^4.0.1",
         "chai-as-promised": "^7.1.0",
         "chai-bignumber": "^3.0.0",
+        "decimal.js": "^10.2.0",
         "dirty-chai": "^2.0.1",
         "ethereum-types": "^3.0.0",
         "ethereumjs-util": "^5.1.1",

contracts/test-utils/src/index.ts

@@ -54,12 +54,15 @@ export { replaceKeysDeep, shortZip } from './lang_utils';
 export {
     assertIntegerRoughlyEquals,
     assertRoughlyEquals,
+    fromFixed,
     getRandomFloat,
     getRandomInteger,
     getRandomPortion,
     getNumericalDivergence,
     getPercentageOfValue,
     toBaseUnitAmount,
+    toDecimal,
+    toFixed,
 } from './number_utils';
 export { orderHashUtils } from './order_hash';
 export { transactionHashUtils } from './transaction_hash';

contracts/test-utils/src/number_utils.ts

@@ -1,11 +1,24 @@
 import { BigNumber } from '@0x/utils';
 import { Web3Wrapper } from '@0x/web3-wrapper';
 import * as crypto from 'crypto';
+import { Decimal } from 'decimal.js';
 
 import { expect } from './chai_setup';
 import { constants } from './constants';
 import { Numberish } from './types';
 
+Decimal.set({ precision: 80 });
+
+/**
+ * Convert `x` to a `Decimal` type.
+ */
+export function toDecimal(x: Numberish): Decimal {
+    if (BigNumber.isBigNumber(x)) {
+        return new Decimal(x.toString(10));
+    }
+    return new Decimal(x);
+}
+
 /**
  * Generate a random integer between `min` and `max`, inclusive.
  */
@@ -33,6 +46,22 @@ export function getRandomFloat(min: Numberish, max: Numberish): BigNumber {
         .plus(min);
 }
 
+export const FIXED_POINT_BASE = new BigNumber(2).pow(127);
+
+/**
+ * Convert `n` to fixed-point integer represenatation.
+ */
+export function toFixed(n: Numberish): BigNumber {
+    return new BigNumber(n).times(FIXED_POINT_BASE).integerValue();
+}
+
+/**
+ * Convert `n` from fixed-point integer represenatation.
+ */
+export function fromFixed(n: Numberish): BigNumber {
+    return new BigNumber(n).dividedBy(FIXED_POINT_BASE);
+}
+
 /**
  * Converts two decimal numbers to integers with `precision` digits, then returns
  * the absolute difference.