test: crypto createClass instanceof Class

The crypto classes are also exposed as createClass for each class. This
tests that each of them returns an instance of the class in question.

PR-URL: nodejs/node#8188
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/parallel/test-crypto-classes.js

@@ -0,0 +1,31 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+
+if (!common.hasCrypto) {
+  common.skip('missing crypto');
+  return;
+}
+const crypto = require('crypto');
+
+// 'ClassName' : ['args', 'for', 'constructor']
+const TEST_CASES = {
+  'Hash': ['sha1'],
+  'Hmac': ['sha1', 'Node'],
+  'Cipheriv': ['des-ede3-cbc', '0123456789abcd0123456789', '12345678'],
+  'Decipheriv': ['des-ede3-cbc', '0123456789abcd0123456789', '12345678'],
+  'Sign': ['RSA-SHA1'],
+  'Verify': ['RSA-SHA1'],
+  'DiffieHellman': [1024],
+  'DiffieHellmanGroup': ['modp5'],
+  'Credentials': []
+};
+
+if (!common.hasFipsCrypto) {
+  TEST_CASES.Cipher = ['aes192', 'secret'];
+  TEST_CASES.Decipher = ['aes192', 'secret'];
+}
+
+for (const [clazz, args] of Object.entries(TEST_CASES)) {
+  assert(crypto[`create${clazz}`](...args) instanceof crypto[clazz]);
+}