test: add message verification on assert.throws

Add regular expression for error message validation to instances of
assert.throws() in test-assert.js.

PR-URL: nodejs#10890
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/parallel/test-assert.js

@@ -90,11 +90,16 @@ assert.doesNotThrow(makeBlock(a.deepEqual, /a/g, /a/g));
 assert.doesNotThrow(makeBlock(a.deepEqual, /a/i, /a/i));
 assert.doesNotThrow(makeBlock(a.deepEqual, /a/m, /a/m));
 assert.doesNotThrow(makeBlock(a.deepEqual, /a/igm, /a/igm));
-assert.throws(makeBlock(a.deepEqual, /ab/, /a/));
-assert.throws(makeBlock(a.deepEqual, /a/g, /a/));
-assert.throws(makeBlock(a.deepEqual, /a/i, /a/));
-assert.throws(makeBlock(a.deepEqual, /a/m, /a/));
-assert.throws(makeBlock(a.deepEqual, /a/igm, /a/im));
+assert.throws(makeBlock(a.deepEqual, /ab/, /a/),
+              /^AssertionError: \/ab\/ deepEqual \/a\/$/);
+assert.throws(makeBlock(a.deepEqual, /a/g, /a/),
+              /^AssertionError: \/a\/g deepEqual \/a\/$/);
+assert.throws(makeBlock(a.deepEqual, /a/i, /a/),
+              /^AssertionError: \/a\/i deepEqual \/a\/$/);
+assert.throws(makeBlock(a.deepEqual, /a/m, /a/),
+              /^AssertionError: \/a\/m deepEqual \/a\/$/);
+assert.throws(makeBlock(a.deepEqual, /a/igm, /a/im),
+              /^AssertionError: \/a\/gim deepEqual \/a\/im$/);
 
 {
   const re1 = /a/;