test: swapped == and equal to === and strictEqual

Line 21 used '==' for a Number comparison, changed to '===''.
Lines 36 and 46 used 'assert.equal', changed to 'assert.strictEqual'.
Lines 2, 3 and 4 require statements used var, changed to const.

PR-URL: https://github.com/nodejs/node/pull/8472


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>