diff --git a/cara/tests/test_expiration.py b/cara/tests/test_expiration.py
new file mode 100644
index 00000000..7638d613
--- /dev/null
+++ b/cara/tests/test_expiration.py
@@ -0,0 +1,29 @@
+import re
+
+import numpy as np
+import numpy.testing as npt
+import pytest
+
+from cara import models
+
+
+def test_multiple_wrong_weight_size():
+    weights = (1., 2., 3.)
+    e_base = models.Expiration((0.084, 0.009, 0.003, 0.002))
+    with pytest.raises(
+            ValueError,
+            match=re.escape("expirations and weigths should contain the"
+                            "same number of elements")
+    ):
+        e = models.MultipleExpiration([e_base, e_base], weights)
+
+
+def test_multiple():
+    weights = (1., 2.)
+    e1 = models.Expiration((0.03, 0.02, 0.01, 0.005))
+    e2 = models.Expiration((0.05, 0.04, 0.03, 0.01))
+    e = models.MultipleExpiration([e1, e2], weights)
+    assert e.aerosols(models.Mask.types['No mask']) == (
+              e1.aerosols(models.Mask.types['No mask'])/3. +
+            2*e2.aerosols(models.Mask.types['No mask'])/3.
+    )