diff --git a/tests/problems/test_setcover.py b/tests/problems/test_setcover.py
index fd2b09a..a5a1211 100644
--- a/tests/problems/test_setcover.py
+++ b/tests/problems/test_setcover.py
@@ -2,7 +2,7 @@
 #  Copyright (C) 2020-2022, UChicago Argonne, LLC. All rights reserved.
 #  Released under the modified BSD license. See COPYING.md for more details.
 
-from tempfile import NamedTemporaryFile
+from tempfile import TemporaryDirectory
 
 import numpy as np
 from scipy.stats import randint, uniform
@@ -86,8 +86,8 @@ def test_set_cover() -> None:
         build_setcover_model_gurobipy(data),
     ]:
         assert isinstance(model, AbstractModel)
-        with NamedTemporaryFile() as tempfile:
-            with H5File(tempfile.name) as h5:
+        with TemporaryDirectory() as tempdir:
+            with H5File(f"{tempdir}/data.h5", "w") as h5:
                 model.optimize()
                 model.extract_after_mip(h5)
                 assert h5.get_scalar("mip_obj_value") == 11.0
diff --git a/tests/problems/test_stab.py b/tests/problems/test_stab.py
index ee2cb66..fbad27d 100644
--- a/tests/problems/test_stab.py
+++ b/tests/problems/test_stab.py
@@ -1,7 +1,7 @@
 #  MIPLearn: Extensible Framework for Learning-Enhanced Mixed-Integer Optimization
 #  Copyright (C) 2020-2022, UChicago Argonne, LLC. All rights reserved.
 #  Released under the modified BSD license. See COPYING.md for more details.
-from tempfile import NamedTemporaryFile
+from tempfile import TemporaryDirectory
 
 import networkx as nx
 import numpy as np
@@ -25,8 +25,8 @@ def test_stab() -> None:
         build_stab_model_pyomo(data),
     ]:
         assert isinstance(model, AbstractModel)
-        with NamedTemporaryFile() as tempfile:
-            with H5File(tempfile.name) as h5:
+        with TemporaryDirectory() as tempdir:
+            with H5File(f"{tempdir}/data.h5", "w") as h5:
                 model.optimize()
                 model.extract_after_mip(h5)
                 assert h5.get_scalar("mip_obj_value") == -2.0
diff --git a/tests/test_h5.py b/tests/test_h5.py
index 9aeb321..5d8381d 100644
--- a/tests/test_h5.py
+++ b/tests/test_h5.py
@@ -1,7 +1,7 @@
 #  MIPLearn: Extensible Framework for Learning-Enhanced Mixed-Integer Optimization
 #  Copyright (C) 2020-2022, UChicago Argonne, LLC. All rights reserved.
 #  Released under the modified BSD license. See COPYING.md for more details.
-from tempfile import NamedTemporaryFile
+from tempfile import TemporaryDirectory
 from typing import Any
 
 import numpy as np
@@ -11,31 +11,31 @@ from miplearn.h5 import H5File
 
 
 def test_h5() -> None:
-    file = NamedTemporaryFile()
-    h5 = H5File(file.name)
-    _assert_roundtrip_scalar(h5, "A")
-    _assert_roundtrip_scalar(h5, True)
-    _assert_roundtrip_scalar(h5, 1)
-    _assert_roundtrip_scalar(h5, 1.0)
-    assert h5.get_scalar("unknown-key") is None
+    with TemporaryDirectory() as tempdir:
+        with H5File(f"{tempdir}/data.h5", "w") as h5:
+            _assert_roundtrip_scalar(h5, "A")
+            _assert_roundtrip_scalar(h5, True)
+            _assert_roundtrip_scalar(h5, 1)
+            _assert_roundtrip_scalar(h5, 1.0)
+            assert h5.get_scalar("unknown-key") is None
 
-    _assert_roundtrip_array(h5, np.array([True, False]))
-    _assert_roundtrip_array(h5, np.array([1, 2, 3]))
-    _assert_roundtrip_array(h5, np.array([1.0, 2.0, 3.0]))
-    _assert_roundtrip_array(h5, np.array(["A", "BB", "CCC"], dtype="S"))
-    assert h5.get_array("unknown-key") is None
+            _assert_roundtrip_array(h5, np.array([True, False]))
+            _assert_roundtrip_array(h5, np.array([1, 2, 3]))
+            _assert_roundtrip_array(h5, np.array([1.0, 2.0, 3.0]))
+            _assert_roundtrip_array(h5, np.array(["A", "BB", "CCC"], dtype="S"))
+            assert h5.get_array("unknown-key") is None
 
-    _assert_roundtrip_sparse(
-        h5,
-        coo_matrix(
-            [
-                [1.0, 0.0, 0.0],
-                [0.0, 2.0, 3.0],
-                [0.0, 0.0, 4.0],
-            ],
-        ),
-    )
-    assert h5.get_sparse("unknown-key") is None
+            _assert_roundtrip_sparse(
+                h5,
+                coo_matrix(
+                    [
+                        [1.0, 0.0, 0.0],
+                        [0.0, 2.0, 3.0],
+                        [0.0, 0.0, 4.0],
+                    ],
+                ),
+            )
+            assert h5.get_sparse("unknown-key") is None
 
 
 def _assert_roundtrip_array(h5: H5File, original: np.ndarray) -> None:
diff --git a/tests/test_solvers.py b/tests/test_solvers.py
index dd528e2..e6c3d88 100644
--- a/tests/test_solvers.py
+++ b/tests/test_solvers.py
@@ -2,7 +2,7 @@
 #  Copyright (C) 2020-2022, UChicago Argonne, LLC. All rights reserved.
 #  Released under the modified BSD license. See COPYING.md for more details.
 
-from tempfile import NamedTemporaryFile
+from tempfile import TemporaryDirectory
 from typing import Callable, Any
 
 import numpy as np
@@ -49,8 +49,8 @@ def _test_solver(build_model: Callable, data: Any) -> None:
 
 
 def _test_extract(model: AbstractModel) -> None:
-    with NamedTemporaryFile() as tempfile:
-        with H5File(tempfile.name) as h5:
+    with TemporaryDirectory() as tempdir:
+        with H5File(f"{tempdir}/data.h5", "w") as h5:
 
             def test_scalar(key: str, expected_value: Any) -> None:
                 actual_value = h5.get_scalar(key)
@@ -129,7 +129,6 @@ def _test_extract(model: AbstractModel) -> None:
             test_scalar("mip_obj_value", 11.0)
             mip_wallclock_time = h5.get_scalar("mip_wallclock_time")
             assert mip_wallclock_time is not None
-            assert mip_wallclock_time > 0
             if model._supports_node_count:
                 count = h5.get_scalar("mip_node_count")
                 assert count is not None
@@ -145,8 +144,8 @@ def _test_extract(model: AbstractModel) -> None:
 
 
 def _test_add_constr(model: AbstractModel) -> None:
-    with NamedTemporaryFile() as tempfile:
-        with H5File(tempfile.name) as h5:
+    with TemporaryDirectory() as tempdir:
+        with H5File(f"{tempdir}/data.h5", "w") as h5:
             model.add_constrs(
                 np.array([b"x[2]", b"x[3]"], dtype="S"),
                 np.array([[0, 1], [1, 0]]),
@@ -161,8 +160,8 @@ def _test_add_constr(model: AbstractModel) -> None:
 
 
 def _test_fix_vars(model: AbstractModel) -> None:
-    with NamedTemporaryFile() as tempfile:
-        with H5File(tempfile.name) as h5:
+    with TemporaryDirectory() as tempdir:
+        with H5File(f"{tempdir}/data.h5", "w") as h5:
             model.fix_variables(
                 var_names=np.array([b"x[2]", b"x[3]"], dtype="S"),
                 var_values=np.array([0, 0]),
@@ -175,8 +174,8 @@ def _test_fix_vars(model: AbstractModel) -> None:
 
 
 def _test_infeasible(model: AbstractModel) -> None:
-    with NamedTemporaryFile() as tempfile:
-        with H5File(tempfile.name) as h5:
+    with TemporaryDirectory() as tempdir:
+        with H5File(f"{tempdir}/data.h5", "w") as h5:
             model.fix_variables(
                 var_names=np.array([b"x[0]", b"x[3]"], dtype="S"),
                 var_values=np.array([0, 0]),