test: improve the code in test-process-hrtime

* use const instead of var
* use assert.strictEqual instead of assert.equal and plain assert
* use arrow functions
* swap assertions arguments to match the standard
* validate the error for assert.throws

PR-URL: nodejs#10667
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michal Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-process-hrtime.js

@@ -3,7 +3,7 @@ require('../common');
 const assert = require('assert');
 
 // the default behavior, return an Array "tuple" of numbers
-var tuple = process.hrtime();
+const tuple = process.hrtime();
 
 // validate the default behavior
 validateTuple(tuple);
@@ -12,16 +12,16 @@ validateTuple(tuple);
 validateTuple(process.hrtime(tuple));
 
 // test that only an Array may be passed to process.hrtime()
-assert.throws(function() {
+assert.throws(() => {
   process.hrtime(1);
-});
+}, /^TypeError: process.hrtime\(\) only accepts an Array tuple$/);
 
 function validateTuple(tuple) {
   assert(Array.isArray(tuple));
-  assert.equal(2, tuple.length);
-  tuple.forEach(function(v) {
-    assert.equal('number', typeof v);
-    assert(isFinite(v));
+  assert.strictEqual(tuple.length, 2);
+  tuple.forEach((v) => {
+    assert.strictEqual(typeof v, 'number');
+    assert.strictEqual(isFinite(v), true);
   });
 }