Patch the actual numpy import, not just the module

tests/test_no_numpy.py

@@ -0,0 +1,59 @@
+import pytest
+from unittest.mock import patch
+
+
+orig_import = __import__
+
+
+def no_numpy_import(*args, **kwargs):
+    print(args[0])
+    if args and args[0].startswith("numpy"):
+        raise ImportError
+    elif "name" in kwargs and kwargs["name"].startswith("numpy"):
+        raise ImportError
+    else:
+        return orig_import(*args, **kwargs)
+
+
+with patch("builtins.__import__", no_numpy_import):
+    from uncertainties import (
+        correlated_values,
+        correlated_values_norm,
+        correlation_matrix,
+        ufloat,
+    )
+
+
+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])

tests/test_uncertainties.py

@@ -1,18 +1,11 @@
 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,
-    correlated_values,
-    correlated_values_norm,
-    correlation_matrix,
-)
+from uncertainties import umath
 from helpers import (
     power_special_cases,
     power_all_cases,
@@ -1321,39 +1314,3 @@ 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])