test: refactor test-crypto-random

* specify constructor for assert.throws()
* load additional modules only if crypto check passes
* normalize some potentially confusing indentation
* provided actual first and expected second in assertions

PR-URL: https://github.com/nodejs/node/pull/10232
Reviewed-By: Prince John Wesley <princejohnwesley@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

test/parallel/test-crypto-random.js

@@ -1,55 +1,34 @@
 'use strict';
-var common = require('../common');
-var assert = require('assert');
+const common = require('../common');
 
 if (!common.hasCrypto) {
   common.skip('missing crypto');
   return;
 }
-var crypto = require('crypto');
+
+const assert = require('assert');
+const crypto = require('crypto');
 
 crypto.DEFAULT_ENCODING = 'buffer';
 
 // bump, we register a lot of exit listeners
 process.setMaxListeners(256);
 
-[crypto.randomBytes,
-  crypto.pseudoRandomBytes
-].forEach(function(f) {
-  [-1,
-    undefined,
-    null,
-    false,
-    true,
-    {},
-    []
-  ].forEach(function(value) {
-    assert.throws(function() { f(value); });
-    assert.throws(function() { f(value, function() {}); });
+[crypto.randomBytes, crypto.pseudoRandomBytes].forEach(function(f) {
+  [-1, undefined, null, false, true, {}, []].forEach(function(value) {
+    assert.throws(function() { f(value); }, TypeError);
+    assert.throws(function() { f(value, function() {}); }, TypeError);
   });
 
   [0, 1, 2, 4, 16, 256, 1024].forEach(function(len) {
-    f(len, checkCall(function(ex, buf) {
-      assert.equal(null, ex);
-      assert.equal(len, buf.length);
+    f(len, common.mustCall(function(ex, buf) {
+      assert.strictEqual(ex, null);
+      assert.strictEqual(buf.length, len);
       assert.ok(Buffer.isBuffer(buf));
     }));
   });
 });
 
-// assert that the callback is indeed called
-function checkCall(cb, desc) {
-  var called_ = false;
-
-  process.on('exit', function() {
-    assert.equal(true, called_, desc || ('callback not called: ' + cb));
-  });
-
-  return function() {
-    return called_ = true, cb.apply(cb, Array.prototype.slice.call(arguments));
-  };
-}
-
 // #5126, "FATAL ERROR: v8::Object::SetIndexedPropertiesToExternalArrayData()
 // length exceeds max acceptable value"
 assert.throws(function() {