test no numpy

tests/test_uncertainties.py

@@ -1,10 +1,18 @@
 import copy
 import math
 import random  # noqa
+from unittest.mock import patch
+
+import pytest
 
 import uncertainties.core as uncert_core
 from uncertainties.core import ufloat, AffineScalarFunc, ufloat_fromstr
-from uncertainties import umath
+from uncertainties import (
+    umath,
+    correlated_values,
+    correlated_values_norm,
+    correlation_matrix,
+)
 from helpers import (
     power_special_cases,
     power_all_cases,
@@ -1313,3 +1321,39 @@ def test_correlated_values_correlation_mat():
             numpy.array(cov_mat),
             numpy.array(uncert_core.covariance_matrix([x2, y2, z2])),
         )
+
+
+@patch("uncertainties.core.numpy", None)
+def test_no_numpy():
+    nom_values = [1, 2, 3]
+    std_devs = [0.1, 0.2, 0.3]
+    cov = [
+        [1, 0, 0],
+        [0, 1, 0],
+        [0, 0, 1],
+    ]
+
+    with pytest.raises(
+        NotImplementedError,
+        match="not able to import numpy",
+    ):
+        _ = correlated_values(nom_values, cov)
+
+    with pytest.raises(
+        NotImplementedError,
+        match="not able to import numpy",
+    ):
+        _ = correlated_values_norm(
+            list(zip(nom_values, std_devs)),
+            cov,
+        )
+
+    x = ufloat(1, 0.1)
+    y = ufloat(2, 0.2)
+    z = ufloat(3, 0.3)
+
+    with pytest.raises(
+        NotImplementedError,
+        match="not able to import numpy",
+    ):
+        _ = correlation_matrix([x, y, z])