Common::getSniffCode(): add tests

Add initial set of tests for the `Common::getSniffCode()` method.

Related to 146
Related to [review comment in PR 446](#446 (comment)).

tests/Core/Util/Common/GetSniffCodeTest.php

@@ -0,0 +1,80 @@
+<?php
+/**
+ * Tests for the \PHP_CodeSniffer\Util\Common::getSniffCode() method.
+ *
+ * @author    Juliette Reinders Folmer <phpcs_nospam@adviesenzo.nl>
+ * @copyright 2024 PHPCSStandards and contributors
+ * @license   https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/master/licence.txt BSD Licence
+ */
+
+namespace PHP_CodeSniffer\Tests\Core\Util\Common;
+
+use PHP_CodeSniffer\Util\Common;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Tests for the \PHP_CodeSniffer\Util\Common::getSniffCode() method.
+ *
+ * @covers \PHP_CodeSniffer\Util\Common::getSniffCode
+ */
+final class GetSniffCodeTest extends TestCase
+{
+
+
+    /**
+     * Test transforming a sniff class name to a sniff code.
+     *
+     * @param string $fqnClass A fully qualified sniff class name.
+     * @param string $expected Expected function output.
+     *
+     * @dataProvider dataGetSniffCode
+     *
+     * @return void
+     */
+    public function testGetSniffCode($fqnClass, $expected)
+    {
+        $this->assertSame($expected, Common::getSniffCode($fqnClass));
+
+    }//end testGetSniffCode()
+
+
+    /**
+     * Data provider.
+     *
+     * @see testGetSniffCode()
+     *
+     * @return array<string, array<string, string>>
+     */
+    public static function dataGetSniffCode()
+    {
+        return [
+            'PHPCS native sniff'                                  => [
+                'fqnClass' => 'PHP_CodeSniffer\\Standards\\Generic\\Sniffs\\Arrays\\ArrayIndentSniff',
+                'expected' => 'Generic.Arrays.ArrayIndent',
+            ],
+            'Class is a PHPCS native test class'                  => [
+                'fqnClass' => 'PHP_CodeSniffer\\Standards\\Generic\\Tests\\Arrays\\ArrayIndentUnitTest',
+                'expected' => 'Generic.Arrays.ArrayIndent',
+            ],
+            'Sniff in external standard without namespace prefix' => [
+                'fqnClass' => 'MyStandard\\Sniffs\\PHP\\MyNameSniff',
+                'expected' => 'MyStandard.PHP.MyName',
+            ],
+            'Test in external standard without namespace prefix'  => [
+                'fqnClass' => 'MyStandard\\Tests\\PHP\\MyNameSniff',
+                'expected' => 'MyStandard.PHP.MyName',
+            ],
+            'Sniff in external standard with namespace prefix'    => [
+                'fqnClass' => 'Vendor\\Package\\MyStandard\\Sniffs\\Category\\AnalyzeMeSniff',
+                'expected' => 'MyStandard.Category.AnalyzeMe',
+            ],
+            'Test in external standard with namespace prefix'     => [
+                'fqnClass' => 'Vendor\\Package\\MyStandard\\Tests\\Category\\AnalyzeMeUnitTest',
+                'expected' => 'MyStandard.Category.AnalyzeMe',
+            ],
+        ];
+
+    }//end dataGetSniffCode()
+
+
+}//end class