fixes OpenZeppelin#1386

Author: Aniket-Engg

test/math/SafeMath.test.js

@@ -53,13 +53,20 @@ contract('SafeMath', function () {
       (await this.safeMath.mul(a, b)).should.be.bignumber.equal(a.times(b));
     });
 
-    it('handles a zero product correctly', async function () {
+    it('handles a zero product correctly (first number as zero)', async function () {
       const a = new BigNumber(0);
       const b = new BigNumber(5678);
 
       (await this.safeMath.mul(a, b)).should.be.bignumber.equal(a.times(b));
     });
 
+    it('handles a zero product correctly (second number as zero)', async function () {
+      const a = new BigNumber(5678);
+      const b = new BigNumber(0);
+
+      (await this.safeMath.mul(a, b)).should.be.bignumber.equal(a.times(b));
+    });
+
     it('throws a revert error on multiplication overflow', async function () {
       const a = MAX_UINT256;
       const b = new BigNumber(2);
@@ -76,6 +83,20 @@ contract('SafeMath', function () {
       (await this.safeMath.div(a, b)).should.be.bignumber.equal(a.div(b));
     });
 
+    it('handles a zero division correctly', async function () {
+      const a = new BigNumber(0);
+      const b = new BigNumber(5678);
+
+      (await this.safeMath.div(a, b)).should.be.bignumber.equal(a.div(b));
+    });
+
+    it('returns complete number resultant on non-even division', async function () {
+      const a = new BigNumber(7000);
+      const b = new BigNumber(5678);
+
+      (await this.safeMath.div(a, b)).should.be.bignumber.equal(1);
+    });
+
     it('throws a revert error on zero division', async function () {
       const a = new BigNumber(5678);
       const b = new BigNumber(0);