test: add expectWarning to common

There are multiple tests that use the same boilerplate to test that
warnings are correctly emitted. This adds a new common function to do that
and changes the tests to use it.

PR-URL: #8662
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

 Conflicts:
	test/parallel/test-buffer-deprecated.js
	test/parallel/test-repl-deprecated.js

test/common.js

@@ -508,3 +508,16 @@ exports.isAlive = function isAlive(pid) {
     return false;
   }
 };
+
+exports.expectWarning = function(name, expected) {
+  if (typeof expected === 'string')
+    expected = [expected];
+  process.on('warning', exports.mustCall((warning) => {
+    assert.strictEqual(warning.name, name);
+    assert.ok(expected.includes(warning.message),
+              `unexpected error message: "${warning.message}"`);
+    // Remove a warning message after it is seen so that we guarantee that we
+    // get each message only once.
+    expected.splice(expected.indexOf(warning.message), 1);
+  }, expected.length));
+};

test/parallel/test-crypto-deprecated.js

@@ -9,19 +9,10 @@ if (!common.hasCrypto) {
 const crypto = require('crypto');
 const tls = require('tls');
 
-const expected = [
+common.expectWarning('DeprecationWarning', [
   'crypto.Credentials is deprecated. Use tls.SecureContext instead.',
   'crypto.createCredentials is deprecated. Use tls.createSecureContext instead.'
-];
-
-process.on('warning', common.mustCall((warning) => {
-  assert.strictEqual(warning.name, 'DeprecationWarning');
-  assert.notStrictEqual(expected.indexOf(warning.message), -1,
-                        `unexpected error message: "${warning.message}"`);
-  // Remove a warning message after it is seen so that we guarantee that we get
-  // each message only once.
-  expected.splice(expected.indexOf(warning.message), 1);
-}, expected.length));
+]);
 
 // Accessing the deprecated function is enough to trigger the warning event.
 // It does not need to be called. So the assert serves the purpose of both

test/parallel/test-util.js

@@ -121,21 +121,12 @@ assert.strictEqual(util.isFunction(function() {}), true);
 assert.strictEqual(util.isFunction(), false);
 assert.strictEqual(util.isFunction('string'), false);
 
-const expected = [
+common.expectWarning('DeprecationWarning', [
   'util.print is deprecated. Use console.log instead.',
   'util.puts is deprecated. Use console.log instead.',
   'util.debug is deprecated. Use console.error instead.',
   'util.error is deprecated. Use console.error instead.'
-];
-
-process.on('warning', common.mustCall((warning) => {
-  assert.strictEqual(warning.name, 'DeprecationWarning');
-  assert.notStrictEqual(expected.indexOf(warning.message), -1,
-                        `unexpected error message: "${warning.message}"`);
-  // Remove a warning message after it is seen so that we guarantee that we get
-  // each message only once.
-  expected.splice(expected.indexOf(warning.message), 1);
-}, expected.length));
+]);
 
 util.print('test');
 util.puts('test');