test: name test files appropriately

Rename the tests appropriately alongside mentioning the subsystem.
Also, make a few basic changes to make sure the test conforms
to the standard test structure.

This renames:
- test-regress-GH-1531
- test-regress-GH-2245
- test-regress-GH-3238
- test-regress-GH-3542
- test-regress-GH-3739
- test-regress-GH-4256

PR-URL: #19212
Refs: #19105
Refs: https://github.com/nodejs/node/blob/master/doc/guides/writing-tests.md#test-structure
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-regress-GH-3238.js → test/parallel/test-cluster-kill-disconnect.js

@@ -1,5 +1,11 @@
 'use strict';
 const common = require('../common');
+
+// Check that cluster works perfectly for both `kill` and `disconnect` cases.
+// Also take into account that the `disconnect` event may be received after the
+// `exit` event.
+// https://github.com/nodejs/node/issues/3238
+
 const assert = require('assert');
 const cluster = require('cluster');
 

test/parallel/test-regress-GH-2245.js → test/parallel/test-eval-strict-referenceerror.js

@@ -1,12 +1,11 @@
 /* eslint-disable strict */
 require('../common');
-const assert = require('assert');
 
-/*
-In Node.js 0.10, a bug existed that caused strict functions to not capture
-their environment when evaluated. When run in 0.10 `test()` fails with a
-`ReferenceError`. See https://github.com/nodejs/node/issues/2245 for details.
-*/
+// In Node.js 0.10, a bug existed that caused strict functions to not capture
+// their environment when evaluated. When run in 0.10 `test()` fails with a
+// `ReferenceError`. See https://github.com/nodejs/node/issues/2245 for details.
+
+const assert = require('assert');
 
 function test() {
 

test/parallel/test-regress-GH-3739.js → test/parallel/test-fs-existssync-false.js

@@ -1,12 +1,15 @@
 'use strict';
-
 const common = require('../common');
+const tmpdir = require('../common/tmpdir');
+
+// This test ensures that fs.existsSync doesn't incorrectly return false.
+// (especially on Windows)
+// https://github.com/nodejs/node-v0.x-archive/issues/3739
+
 const assert = require('assert');
 const fs = require('fs');
 const path = require('path');
 
-const tmpdir = require('../common/tmpdir');
-
 let dir = path.resolve(tmpdir.path);
 
 // Make sure that the tmp directory is clean

test/parallel/test-regress-GH-3542.js → test/parallel/test-fs-readfilesync-enoent.js

@@ -1,9 +1,14 @@
 'use strict';
 const common = require('../common');
+
 // This test is only relevant on Windows.
 if (!common.isWindows)
   common.skip('Windows specific test.');
 
+// This test ensures fs.realpathSync works on properly on Windows without
+// throwing ENOENT when the path involves a fileserver.
+// https://github.com/nodejs/node-v0.x-archive/issues/3542
+
 const assert = require('assert');
 const fs = require('fs');
 const path = require('path');

test/parallel/test-regress-GH-1531.js → test/parallel/test-http-request-agent.js

@@ -1,15 +1,15 @@
 'use strict';
 const common = require('../common');
 
-// This test ensures that a http request callback is called
-// when the agent option is set
-// See https://github.com/nodejs/node-v0.x-archive/issues/1531
-
 if (!common.hasCrypto)
   common.skip('missing crypto');
 
 const fixtures = require('../common/fixtures');
 
+// This test ensures that a http request callback is called when the agent
+// option is set.
+// See https://github.com/nodejs/node-v0.x-archive/issues/1531
+
 const https = require('https');
 
 const options = {

test/parallel/test-regress-GH-4256.js → test/parallel/test-process-domain-segfault.js

@@ -21,6 +21,11 @@
 
 'use strict';
 require('../common');
+
+// This test ensures that setting `process.domain` to `null` does not result in
+// node crashing with a segfault.
+// https://github.com/nodejs/node-v0.x-archive/issues/4256
+
 process.domain = null;
 setTimeout(function() {
   console.log('this console.log statement should not make node crash');