Implement SchemaFinder::available()

src/Util/Xml/SchemaFinder.php

@@ -9,16 +9,43 @@
  */
 namespace PHPUnit\Util\Xml;
 
+use function assert;
 use function defined;
 use function is_file;
+use function rsort;
 use function sprintf;
+use DirectoryIterator;
 use PHPUnit\Runner\Version;
 
 /**
  * @internal This class is not covered by the backward compatibility promise for PHPUnit
  */
 final class SchemaFinder
 {
+    /**
+     * @psalm-return non-empty-list<non-empty-string>
+     */
+    public function available(): array
+    {
+        $result = [Version::series()];
+
+        foreach ((new DirectoryIterator($this->path() . 'schema')) as $file) {
+            if ($file->isDot()) {
+                continue;
+            }
+
+            $version = $file->getBasename('.xsd');
+
+            assert(!empty($version));
+
+            $result[] = $version;
+        }
+
+        rsort($result);
+
+        return $result;
+    }
+
     /**
      * @throws Exception
      */

tests/unit/Util/Xml/SchemaFinderTest.php

@@ -9,6 +9,7 @@
  */
 namespace PHPUnit\Util\Xml;
 
+use function count;
 use PHPUnit\Framework\TestCase;
 use PHPUnit\Runner\Version;
 
@@ -19,12 +20,20 @@
  */
 final class SchemaFinderTest extends TestCase
 {
-    public function testFindsExistingSchemaForComposerInstallation(): void
+    public function testListsAvailableSchemas(): void
+    {
+        $schemas = (new SchemaFinder)->available();
+
+        $this->assertSame((new Version)->series(), $schemas[0]);
+        $this->assertSame('8.5', $schemas[count($schemas) - 1]);
+    }
+
+    public function testFindsExistingSchema(): void
     {
         $this->assertFileExists((new SchemaFinder)->find((new Version)->series()));
     }
 
-    public function testDoesNotFindNonExistentSchemaForComposerInstallation(): void
+    public function testDoesNotFindNonExistentSchema(): void
     {
         $this->expectException(Exception::class);