diff --git a/test_app.py b/test_app.py
index e0aeb4f..998c3d8 100644
--- a/test_app.py
+++ b/test_app.py
@@ -147,4 +147,85 @@ def test_werktage_berechnung(client):
     })
     assert resp.status_code == 200
     assert b'Anzahl der Werktage' in resp.data
-    assert f': {expected}'.encode() in resp.data 
\ No newline at end of file
+    assert f': {expected}'.encode() in resp.data 
+
+def test_api_tage_werktage(client):
+    # Erfolgsfall: Werktage
+    resp = client.post('/api/tage_werktage', json={
+        'start': '2024-06-01', 'end': '2024-06-10', 'werktage': True
+    })
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert 'result' in data
+    # Fehlerfall: Ungültiges Datum
+    resp = client.post('/api/tage_werktage', json={
+        'start': 'foo', 'end': 'bar', 'werktage': True
+    })
+    assert resp.status_code == 400
+    data = resp.get_json()
+    assert 'error' in data
+
+def test_api_wochentag(client):
+    resp = client.post('/api/wochentag', json={'datum': '2024-06-10'})
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert data['result'] == 'Montag'
+    # Fehlerfall
+    resp = client.post('/api/wochentag', json={'datum': 'foo'})
+    assert resp.status_code == 400
+    assert 'error' in resp.get_json()
+
+def test_api_kw_berechnen(client):
+    resp = client.post('/api/kw_berechnen', json={'datum': '2024-06-10'})
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert 'KW' in data['result']
+    # Fehlerfall
+    resp = client.post('/api/kw_berechnen', json={'datum': 'foo'})
+    assert resp.status_code == 400
+    assert 'error' in resp.get_json()
+
+def test_api_kw_datum(client):
+    resp = client.post('/api/kw_datum', json={'jahr': 2024, 'kw': 24})
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert 'result' in data and 'start' in data and 'end' in data
+    # Fehlerfall
+    resp = client.post('/api/kw_datum', json={'jahr': 'foo', 'kw': 'bar'})
+    assert resp.status_code == 400
+    assert 'error' in resp.get_json()
+
+def test_api_plusminus(client):
+    # Tage addieren
+    resp = client.post('/api/plusminus', json={
+        'datum': '2024-06-10', 'anzahl': 5, 'einheit': 'tage', 'richtung': 'add', 'werktage': False
+    })
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert data['result'] == '2024-06-15'
+    # Werktage subtrahieren
+    resp = client.post('/api/plusminus', json={
+        'datum': '2024-06-10', 'anzahl': 5, 'einheit': 'tage', 'richtung': 'sub', 'werktage': True
+    })
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert 'result' in data
+    # Fehlerfall: ungültige Einheit
+    resp = client.post('/api/plusminus', json={
+        'datum': '2024-06-10', 'anzahl': 5, 'einheit': 'foo'
+    })
+    assert resp.status_code == 400
+    assert 'error' in resp.get_json()
+
+def test_api_stats(client):
+    resp = client.get('/api/stats')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert 'pageviews' in data and 'func_counts' in data and 'impressions_per_day' in data
+
+def test_api_monitor(client):
+    resp = client.get('/api/monitor')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert data['status'] == 'ok'
+    assert 'uptime_seconds' in data 
\ No newline at end of file