diff --git a/tests/src/MapHandlerTest.php b/tests/src/MapHandlerTest.php
index 7309913b..0fe3546c 100644
--- a/tests/src/MapHandlerTest.php
+++ b/tests/src/MapHandlerTest.php
@@ -4,6 +4,8 @@
 
 use FileEye\MimeMap\Extension;
 use FileEye\MimeMap\MalformedTypeException;
+use FileEye\MimeMap\Map\DefaultMap;
+use FileEye\MimeMap\Map\EmptyMap;
 use FileEye\MimeMap\Map\MimeMapInterface;
 use FileEye\MimeMap\MapHandler;
 use FileEye\MimeMap\MappingException;
@@ -21,6 +23,15 @@ public function setUp(): void
         $this->map = MapHandler::map();
     }
 
+    public function testSetDefaultMapClass(): void
+    {
+        MapHandler::setDefaultMapClass(EmptyMap::class);
+        $this->assertInstanceOf(EmptyMap::class, MapHandler::map());
+        MapHandler::setDefaultMapClass(DefaultMap::class);
+        // @phpstan-ignore method.impossibleType
+        $this->assertInstanceOf(DefaultMap::class, MapHandler::map());
+    }
+
     public function testMap(): void
     {
         $this->assertStringContainsString('DefaultMap.php', $this->map->getFileName());
@@ -37,8 +48,10 @@ public function testAdd(): void
     {
         // Adding a new type with a new extension.
         $this->map->addTypeExtensionMapping('bingo/bongo', 'bngbng');
+        $this->map->addTypeDescription('bingo/bongo', 'Bingo, Bongo!');
         $this->assertSame(['bngbng'], (new Type('bingo/bongo'))->getExtensions());
         $this->assertSame('bngbng', (new Type('bingo/bongo'))->getDefaultExtension());
+        $this->assertSame('Bingo, Bongo!', (new Type('bingo/bongo'))->getDescription());
         $this->assertSame(['bingo/bongo'], (new Extension('bngbng'))->getTypes());
         $this->assertSame('bingo/bongo', (new Extension('bngbng'))->getDefaultType());
 
@@ -190,6 +203,14 @@ public function testSetExtensionDefaultType(): void
         $this->assertSame(['image/vnd.dvb.subtitle', 'text/vnd.dvb.subtitle', 'text/x-microdvd', 'text/x-mpsub', 'text/x-subviewer'], (new Extension('SUB'))->getTypes());
     }
 
+    public function testAddAliasToType(): void
+    {
+        $this->assertSame(['image/psd', 'image/x-psd', 'image/photoshop', 'image/x-photoshop', 'application/photoshop', 'application/x-photoshop',], (new Type('image/vnd.adobe.photoshop'))->getAliases());
+        $this->map->addTypeAlias('image/vnd.adobe.photoshop', 'application/x-foo-bar');
+        $this->assertSame(['image/psd', 'image/x-psd', 'image/photoshop', 'image/x-photoshop', 'application/photoshop', 'application/x-photoshop', 'application/x-foo-bar',], (new Type('image/vnd.adobe.photoshop'))->getAliases());
+        $this->assertContains('application/x-foo-bar', $this->map->listAliases());
+    }
+
     public function testReAddAliasToType(): void
     {
         $this->assertSame(['image/psd', 'image/x-psd', 'image/photoshop', 'image/x-photoshop', 'application/photoshop', 'application/x-photoshop',], (new Type('image/vnd.adobe.photoshop'))->getAliases());
diff --git a/tests/src/MapUpdaterTest.php b/tests/src/MapUpdaterTest.php
index 921ac7c3..f7b36daf 100644
--- a/tests/src/MapUpdaterTest.php
+++ b/tests/src/MapUpdaterTest.php
@@ -171,6 +171,22 @@ public function testWriteMapToPhpClassFile(): void
         $this->fileSystem->remove(__DIR__ . '/../fixtures/MiniMap.php');
     }
 
+    public function testWriteMapToPhpClassFileFailure(): void
+    {
+        $this->fileSystem->copy(__DIR__ . '/../fixtures/MiniMap.php.test', __DIR__ . '/../fixtures/MiniMap.php');
+        include_once(__DIR__ . '/../fixtures/MiniMap.php');
+        // @phpstan-ignore class.notFound, argument.type
+        MapHandler::setDefaultMapClass(MiniMap::class);
+        $map_a = MapHandler::map();
+        $this->assertStringContainsString('fixtures/MiniMap.php', $map_a->getFileName());
+        $content = file_get_contents($map_a->getFileName());
+        assert(is_string($content));
+        $this->assertStringNotContainsString('text/plain', $content);
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage("Failed loading file foo://bar.stub");
+        $this->updater->writeMapToPhpClassFile("foo://bar.stub");
+    }
+
     public function testGetDefaultMapBuildFile(): void
     {
         $this->assertStringContainsString('default_map_build.yml', MapUpdater::getDefaultMapBuildFile());