Organize test files following contracts folders structure

test/math/SafeMath.test.js

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+import assertRevert from '../helpers/assertRevert';
+const assertJump = require('../helpers/assertJump');
+var SafeMathMock = artifacts.require('mocks/SafeMathMock.sol');
+
+contract('SafeMath', function (accounts) {
+  let safeMath;
+
+  before(async function () {
+    safeMath = await SafeMathMock.new();
+  });
+
+  it('multiplies correctly', async function () {
+    let a = 5678;
+    let b = 1234;
+    await safeMath.multiply(a, b);
+    let result = await safeMath.result();
+    assert.equal(result, a * b);
+  });
+
+  it('adds correctly', async function () {
+    let a = 5678;
+    let b = 1234;
+    await safeMath.add(a, b);
+    let result = await safeMath.result();
+
+    assert.equal(result, a + b);
+  });
+
+  it('subtracts correctly', async function () {
+    let a = 5678;
+    let b = 1234;
+    await safeMath.subtract(a, b);
+    let result = await safeMath.result();
+
+    assert.equal(result, a - b);
+  });
+
+  it('should throw an error if subtraction result would be negative', async function () {
+    let a = 1234;
+    let b = 5678;
+    try {
+      await safeMath.subtract(a, b);
+      assert.fail('should have thrown before');
+    } catch (error) {
+      assertJump(error);
+    }
+  });
+
+  it('should throw an error on addition overflow', async function () {
+    let a = 115792089237316195423570985008687907853269984665640564039457584007913129639935;
+    let b = 1;
+    await assertRevert(safeMath.add(a, b));
+  });
+
+  it('should throw an error on multiplication overflow', async function () {
+    let a = 115792089237316195423570985008687907853269984665640564039457584007913129639933;
+    let b = 2;
+    await assertRevert(safeMath.multiply(a, b));
+  });
+});