diff --git a/src/test/java/dev/kruhlmann/imgfloat/service/AssetCleanupServiceTest.java b/src/test/java/dev/kruhlmann/imgfloat/service/AssetCleanupServiceTest.java
new file mode 100644
index 0000000..6e8384e
--- /dev/null
+++ b/src/test/java/dev/kruhlmann/imgfloat/service/AssetCleanupServiceTest.java
@@ -0,0 +1,101 @@
+package dev.kruhlmann.imgfloat.service;
+
+import static org.mockito.ArgumentMatchers.anySet;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import dev.kruhlmann.imgfloat.model.db.imgfloat.Asset;
+import dev.kruhlmann.imgfloat.model.db.imgfloat.ScriptAsset;
+import dev.kruhlmann.imgfloat.model.db.imgfloat.ScriptAssetAttachment;
+import dev.kruhlmann.imgfloat.repository.AssetRepository;
+import dev.kruhlmann.imgfloat.repository.ScriptAssetAttachmentRepository;
+import dev.kruhlmann.imgfloat.repository.ScriptAssetRepository;
+import dev.kruhlmann.imgfloat.model.AssetType;
+import java.util.List;
+import java.util.Set;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentCaptor;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class AssetCleanupServiceTest {
+
+    private AssetRepository assetRepository;
+    private AssetStorageService assetStorageService;
+    private ScriptAssetAttachmentRepository attachmentRepository;
+    private ScriptAssetRepository scriptAssetRepository;
+    private AssetCleanupService service;
+
+    @BeforeEach
+    void setup() {
+        assetRepository = mock(AssetRepository.class);
+        assetStorageService = mock(AssetStorageService.class);
+        attachmentRepository = mock(ScriptAssetAttachmentRepository.class);
+        scriptAssetRepository = mock(ScriptAssetRepository.class);
+        service = new AssetCleanupService(
+            assetRepository, assetStorageService, attachmentRepository, scriptAssetRepository
+        );
+    }
+
+    @Test
+    void cleanupPassesAllReferencedIdsToStorageService() {
+        Asset asset = new Asset("broadcaster", AssetType.IMAGE);
+        String assetId = asset.getId(); // UUID generated by constructor
+
+        ScriptAsset script = new ScriptAsset();
+        script.setId("script-1");
+        script.setSourceFileId("source-file-1");
+        script.setLogoFileId("logo-file-1");
+
+        ScriptAssetAttachment attachment = new ScriptAssetAttachment("script-1", "attach.png");
+        attachment.setFileId("attachment-file-1");
+
+        when(assetRepository.findAll()).thenReturn(List.of(asset));
+        when(scriptAssetRepository.findAll()).thenReturn(List.of(script));
+        when(attachmentRepository.findAll()).thenReturn(List.of(attachment));
+
+        service.cleanup();
+
+        ArgumentCaptor<Set<String>> captor = ArgumentCaptor.forClass((Class) Set.class);
+        verify(assetStorageService).deleteOrphanedAssets(captor.capture());
+        Set<String> referenced = captor.getValue();
+        assertThat(referenced).contains(assetId, "source-file-1", "logo-file-1", "attachment-file-1");
+    }
+
+    @Test
+    void cleanupIncludesAttachmentIdWhenFileIdIsNull() {
+        ScriptAssetAttachment attachment = new ScriptAssetAttachment("script-1", "attach.png");
+        attachment.setId("fallback-id");
+        attachment.setFileId(null);
+
+        when(assetRepository.findAll()).thenReturn(List.of());
+        when(scriptAssetRepository.findAll()).thenReturn(List.of());
+        when(attachmentRepository.findAll()).thenReturn(List.of(attachment));
+
+        service.cleanup();
+
+        ArgumentCaptor<Set<String>> captor = ArgumentCaptor.forClass((Class) Set.class);
+        verify(assetStorageService).deleteOrphanedAssets(captor.capture());
+        assertThat(captor.getValue()).contains("fallback-id");
+    }
+
+    @Test
+    void cleanupSkipsBlankScriptFileIds() {
+        ScriptAsset script = new ScriptAsset();
+        script.setId("script-1");
+        script.setSourceFileId(null);
+        script.setLogoFileId("  ");
+
+        when(assetRepository.findAll()).thenReturn(List.of());
+        when(scriptAssetRepository.findAll()).thenReturn(List.of(script));
+        when(attachmentRepository.findAll()).thenReturn(List.of());
+
+        service.cleanup();
+
+        ArgumentCaptor<Set<String>> captor = ArgumentCaptor.forClass((Class) Set.class);
+        verify(assetStorageService).deleteOrphanedAssets(captor.capture());
+        assertThat(captor.getValue()).doesNotContain("  ").doesNotContain("script-1");
+    }
+}
diff --git a/src/test/java/dev/kruhlmann/imgfloat/util/StringNormalizerTest.java b/src/test/java/dev/kruhlmann/imgfloat/util/StringNormalizerTest.java
new file mode 100644
index 0000000..cd7cb9b
--- /dev/null
+++ b/src/test/java/dev/kruhlmann/imgfloat/util/StringNormalizerTest.java
@@ -0,0 +1,36 @@
+package dev.kruhlmann.imgfloat.util;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class StringNormalizerTest {
+
+    @Test
+    void toLowerCaseRootReturnsNullForNull() {
+        assertThat(StringNormalizer.toLowerCaseRoot(null)).isNull();
+    }
+
+    @Test
+    void toLowerCaseRootConvertsToLowercase() {
+        assertThat(StringNormalizer.toLowerCaseRoot("Hello")).isEqualTo("hello");
+        assertThat(StringNormalizer.toLowerCaseRoot("BROADCASTER")).isEqualTo("broadcaster");
+        assertThat(StringNormalizer.toLowerCaseRoot("MiXeDcAsE")).isEqualTo("mixedcase");
+    }
+
+    @Test
+    void toLowerCaseRootHandlesAlreadyLowercase() {
+        assertThat(StringNormalizer.toLowerCaseRoot("already_lower")).isEqualTo("already_lower");
+    }
+
+    @Test
+    void toLowerCaseRootHandlesEmptyString() {
+        assertThat(StringNormalizer.toLowerCaseRoot("")).isEqualTo("");
+    }
+
+    @Test
+    void toLowerCaseRootUsesRootLocale() {
+        // Turkish locale would uppercase 'i' to 'İ' but ROOT locale must not
+        assertThat(StringNormalizer.toLowerCaseRoot("TITLE")).isEqualTo("title");
+    }
+}