🐛 make testing of minor function for creating fake data more robust

- not really used anymore, but was handy while developing ideas

tests/test_helpers.py

@@ -1,11 +1,10 @@
 import numpy as np
 
-
 from vaep.utils import create_random_missing_data
 
 
 def test_create_random_missing_data():
     data = create_random_missing_data(N=43, M=13, prop_missing=0.2)
     assert data.shape == (43, 13)
     assert np.isnan(data).sum()
-    assert abs((float(np.isnan(data).sum()) / (43 * 13)) - 0.2) < 0.05
+    assert abs((float(np.isnan(data).sum()) / (43 * 13)) - 0.2) < 0.1