diff --git a/src/app/services/filter.helper.spec.ts b/src/app/services/filter.helper.spec.ts
new file mode 100644
index 0000000..9196698
--- /dev/null
+++ b/src/app/services/filter.helper.spec.ts
@@ -0,0 +1,66 @@
+import {Song} from '../modules/songs/services/song';
+import {filterSong} from './filter.helper';
+
+describe('Filter Helper', () => {
+  const song: Song = {
+    title: 'Song Title',
+    text: "This is a songtext, aa?bb!cc,dd.ee'ff",
+    legalOwner: '',
+    label: '',
+    id: '',
+    legalType: '',
+    artist: '',
+    comment: '',
+    edits: [],
+    final: false,
+    flags: '',
+    key: '',
+    number: 1,
+    legalOwnerId: '',
+    origin: '',
+    status: '',
+    tempo: 10,
+    type: '',
+    termsOfUse: '',
+  };
+
+  it('should not find song', () => {
+    void expect(filterSong(song, 'nope')).toBe(false);
+  });
+
+  it('should find song by title', () => {
+    void expect(filterSong(song, 'Song Title')).toBe(true);
+  });
+
+  it('should find song by text', () => {
+    void expect(filterSong(song, 'This is a songtext')).toBe(true);
+  });
+
+  it('should find with spaces', () => {
+    void expect(filterSong(song, 'SongTitle')).toBe(true);
+  });
+
+  it('should find ordinal invariant', () => {
+    void expect(filterSong(song, 'songtitle')).toBe(true);
+  });
+
+  it('should find ? invariant', () => {
+    void expect(filterSong(song, 'aabb')).toBe(true);
+  });
+
+  it('should find ! invariant', () => {
+    void expect(filterSong(song, 'bbcc')).toBe(true);
+  });
+
+  it('should find , invariant', () => {
+    void expect(filterSong(song, 'ccdd')).toBe(true);
+  });
+
+  it('should find . invariant', () => {
+    void expect(filterSong(song, 'ddee')).toBe(true);
+  });
+
+  it('should find apostroph invariant', () => {
+    void expect(filterSong(song, 'eeff')).toBe(true);
+  });
+});
diff --git a/src/app/services/filter.helper.ts b/src/app/services/filter.helper.ts
index b059e86..4c5d0ef 100644
--- a/src/app/services/filter.helper.ts
+++ b/src/app/services/filter.helper.ts
@@ -1,9 +1,7 @@
 import {Song} from '../modules/songs/services/song';
 
 export function filterSong(song: Song, filterValue: string): boolean {
-  if (!filterValue) {
-    return true;
-  }
+  if (!filterValue) return true;
 
   const textMatch = !!song.text && normalize(song.text).indexOf(normalize(filterValue)) !== -1;
   const titleMatch = !!song.title && normalize(song.title).indexOf(normalize(filterValue)) !== -1;
@@ -12,5 +10,5 @@ export function filterSong(song: Song, filterValue: string): boolean {
 }
 
 function normalize(input: string): string {
-  return input.toLowerCase().replace(/\s/g, '');
+  return input.toLowerCase().replace(/[\s?!.,']/g, '');
 }