style: align regexp/reviver with namespace conventions

- Added missing `test/test.main.js` (present in 25/27 siblings, 93%),
  mirroring `test/test.js` but requiring `./../lib/main.js` directly so
  that regressions in `lib/index.js` do not mask bugs in the main
  implementation file.

https://claude.ai/code/session_0151TCuqxNJXJZfy4XEWqKhM

Author: claude

lib/node_modules/@stdlib/regexp/reviver/test/test.main.js

@@ -0,0 +1,123 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2022 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var tape = require( 'tape' );
+var parseJSON = require( '@stdlib/utils/parse-json' );
+var reviveRegExp = require( './../lib/main.js' );
+
+
+// FUNCTIONS //
+
+function setup( pattern, flags ) {
+	return {
+		'type': 'RegExp',
+		'pattern': pattern,
+		'flags': flags || ''
+	};
+}
+
+
+// TESTS //
+
+tape( 'main export is a function', function test( t ) {
+	t.ok( true, __filename );
+	t.strictEqual( typeof reviveRegExp, 'function', 'main export is a function' );
+	t.end();
+});
+
+tape( 'the function does not transform values which are not serialized RegExp objects', function test( t ) {
+	var expected;
+	var actual;
+
+	expected = {
+		'beep': 'boop'
+	};
+	actual = parseJSON( '{"beep":"boop"}', reviveRegExp );
+
+	t.deepEqual( actual, expected, 'returns expected value' );
+
+	// Null edge case:
+	actual = parseJSON( 'null', reviveRegExp );
+	t.strictEqual( actual, null, 'returns expected value' );
+
+	t.end();
+});
+
+tape( 'an object must have a recognized `type` field in order to be revived', function test( t ) {
+	var expected;
+	var actual;
+
+	expected = setup( 'ab+c' );
+	expected.type = 'Boop';
+
+	actual = parseJSON( JSON.stringify( expected ), reviveRegExp );
+	t.deepEqual( actual, expected, 'returns expected value' );
+
+	t.end();
+});
+
+tape( 'an object must have a `pattern` field in order to be revived', function test( t ) {
+	var expected;
+	var actual;
+
+	expected = setup( 'ab+c' );
+	delete expected.pattern;
+
+	actual = parseJSON( JSON.stringify( expected ), reviveRegExp );
+	t.deepEqual( actual, expected, 'returns expected value' );
+
+	t.end();
+});
+
+tape( 'the function revives a JSON-serialized regular expression', function test( t ) {
+	var expected;
+	var patterns;
+	var actual;
+	var flags;
+	var json;
+	var i;
+
+	patterns = [
+		'.*',
+		'ab+c',
+		'/.*^1',
+		'a+.b*'
+	];
+
+	flags = [
+		'd',
+		'dy',
+		's',
+		''
+	];
+
+	for ( i = 0; i < patterns.length; i++ ) {
+		json = JSON.stringify( setup( patterns[ i ], flags[ i ] ) );
+
+		expected = new RegExp( patterns[ i ], flags[ i ] );
+		actual = parseJSON( json, reviveRegExp );
+
+		t.ok( actual instanceof RegExp, 'returns expected value' );
+		t.strictEqual( actual.toString(), expected.toString(), 'returns expected value when provided ' + json );
+	}
+	t.end();
+});