test: add tests for max64 and min64 from Math

test/Math.test.js

+var MathMock = artifacts.require('./mocks/MathMock.sol');
+
+contract('Math', function (accounts) {
+  let math;
+
+  before(async function () {
+    math = await MathMock.new();
+  });
+
+  it('returns max correctly', async function () {
+    let a = 5678;
+    let b = 1234;
+    await math.max64(a, b);
+    let result = await math.result();
+    assert.equal(result, a);
+  });
+
+  it('returns min correctly', async function () {
+    let a = 5678;
+    let b = 1234;
+    await math.min64(a, b);
+    let result = await math.result();
+    assert.equal(result, b);
+  });
+
+});

test/mocks/MathMock.sol

+pragma solidity ^0.4.18;
+
+
+import '../../contracts/math/Math.sol';
+
+
+contract MathMock {
+  uint64 public result;
+
+  function max64(uint64 a, uint64 b) public {
+    result = Math.max64(a, b);
+  }
+
+  function min64(uint64 a, uint64 b) public {
+    result = Math.min64(a, b);
+  }
+}