begin tests

src/utils/formatTime.js

@@ -22,10 +22,11 @@ export default function formatTime (milliseconds) {
   const oneHour = 3600000;
   const oneMinute = 60000;
   const oneSecond = 1000;
-  const seconds = 0;
-  const minutes = 0;
-  const hours = 0;
-  const result = '';
+
+  let seconds = 0;
+  let minutes = 0;
+  let hours = 0;
+  let result = '';
   if (milliseconds === 0) {
     return '0ms';
   }
@@ -69,4 +70,4 @@ export default function formatTime (milliseconds) {
   }
 
   return result;
-};
+}

test/formatTimestamp.test.js

@@ -0,0 +1,30 @@
+/* globals describe it */
+import assert from 'assert';
+
+import fn from '../src/utils/formatTimestamp.js';
+
+const name = 'formatTimestamp';
+
+const timesToTest = [
+  { args: [new Date(2017, 0, 1)], expected: '00:00:00.00' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 0)], expected: '11:33:30.00' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 50)], expected: '11:33:30.05' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 45)], expected: '11:33:30.05' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 40)], expected: '11:33:30.04' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 100)], expected: '11:33:30.10' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 350)], expected: '11:33:30.35' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 340)], expected: '11:33:30.34' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 356)], expected: '11:33:30.36' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 900)], expected: '11:33:30.90' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 990)], expected: '11:33:30.99' },
+  { args: [new Date(2017, 0, 1, 11, 33, 30, 998)], expected: '11:33:30.99' }
+];
+
+describe(name, () => {
+  timesToTest.forEach(t => {
+    it(`should match expected ${t.args[0]}`, () => {
+      const actual = fn(t.args[0]);
+      assert.equal(actual, t.expected);
+    });
+  });
+});