Casting fixture parameter to list at the beginning of parameter… (#5950)

Casting fixture parameter to list at the beginning of parameter parsing.

Author: nicoddemus

changelog/5946.bugfix.rst

@@ -0,0 +1 @@
+Fixed issue when parametrizing fixtures with numpy arrays (and possibly other sequence-like types).

setup.py

@@ -28,6 +28,7 @@ def main():
                 "mock",
                 "nose",
                 "requests",
+                "numpy",
                 "xmlschema",
             ]
         },

src/_pytest/fixtures.py

@@ -1113,6 +1113,9 @@ def fixture(
                 ``fixture_<fixturename>`` and then use
                 ``@pytest.fixture(name='<fixturename>')``.
     """
+    if params is not None:
+        params = list(params)
+
     fixture_function, arguments = _parse_fixture_args(
         callable_or_scope,
         *args,
@@ -1134,8 +1137,6 @@ def fixture(
             fixture_function
         )
 
-    if params is not None and not isinstance(params, (list, tuple)):
-        params = list(params)
     return FixtureFunctionMarker(scope, params, autouse, ids=ids, name=name)
 
 

testing/python/fixtures.py

@@ -4187,3 +4187,21 @@ def test_check_fixture_instantiations():
     )
     result = testdir.runpytest()
     result.assert_outcomes(passed=7)
+
+
+def test_fixture_parametrization_nparray(testdir):
+    testdir.makepyfile(
+        """
+        from numpy import linspace
+        from pytest import fixture
+
+        @fixture(params=linspace(1, 10, 10))
+        def value(request):
+            return request.param
+
+        def test_bug(value):
+            assert value == value
+    """
+    )
+    result = testdir.runpytest()
+    result.assert_outcomes(passed=10)