test: refactor test-crypto-timing-safe-equal

Add RegExp arguments to throws assertions.

PR-URL: nodejs#9843
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Teddy Katz <teddy.katz@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/sequential/test-crypto-timing-safe-equal.js

@@ -23,12 +23,15 @@ assert.strictEqual(
 
 assert.throws(function() {
   crypto.timingSafeEqual(Buffer.from([1, 2, 3]), Buffer.from([1, 2]));
-}, 'should throw when given buffers with different lengths');
+}, /^TypeError: Input buffers must have the same length$/,
+   'should throw when given buffers with different lengths');
 
 assert.throws(function() {
   crypto.timingSafeEqual('not a buffer', Buffer.from([1, 2]));
-}, 'should throw if the first argument is not a buffer');
+}, /^TypeError: First argument must be a buffer$/,
+   'should throw if the first argument is not a buffer');
 
 assert.throws(function() {
   crypto.timingSafeEqual(Buffer.from([1, 2]), 'not a buffer');
-}, 'should throw if the second argument is not a buffer');
+}, /^TypeError: Second argument must be a buffer$/,
+   'should throw if the second argument is not a buffer');