diff --git a/astropy/convolution/tests/test_convolve_fft.py b/astropy/convolution/tests/test_convolve_fft.py
index 964410ccc124..a6eb30dd1544 100644
--- a/astropy/convolution/tests/test_convolve_fft.py
+++ b/astropy/convolution/tests/test_convolve_fft.py
@@ -787,12 +787,12 @@ def test_big_fail(self):
         Test that convolve_fft raises an exception if a too-large array is passed in.
         """
 
-        # note 512**3 * 16 bytes = 2.0 GB
+        # while a good idea, this approach did not work; it actually writes to disk
+        # arr = np.memmap('file.np', mode='w+', shape=(512, 512, 512), dtype=complex)
+        # this just allocates the memory but never touches it; it's better:
         arr = np.empty([512, 512, 512], dtype=complex)
+        # note 512**3 * 16 bytes = 2.0 GB
         with pytest.raises((ValueError, MemoryError)):
-            # while a good idea, this approach did not work; it actually writes to disk
-            # arr = np.memmap('file.np', mode='w+', shape=(512, 512, 512), dtype=complex)
-            # this just allocates the memory but never touches it; it's better:
             convolve_fft(arr, arr)
 
     def test_padding(self):
diff --git a/astropy/convolution/tests/test_kernel_class.py b/astropy/convolution/tests/test_kernel_class.py
index ac607f3e641a..75cd6677f38f 100644
--- a/astropy/convolution/tests/test_kernel_class.py
+++ b/astropy/convolution/tests/test_kernel_class.py
@@ -45,20 +45,7 @@
     AiryDisk2DKernel,
     Ring2DKernel,
 ]
-KERNEL_TYPES_WITH_ARGS = [
-    (AiryDisk2DKernel, (2,)),
-    (Box2DKernel, (2,)),
-    (Gaussian1DKernel, (2,)),
-    (Gaussian2DKernel, (2,)),
-    (RickerWavelet1DKernel, (2,)),
-    (RickerWavelet2DKernel, (2,)),
-    (Model1DKernel, (Gaussian1D(1, 0, 2),)),
-    (Model2DKernel, (Gaussian2D(1, 0, 0, 2, 2),)),
-    (Ring2DKernel, (9, 8)),
-    (Tophat2DKernel, (2,)),
-    (Trapezoid1DKernel, (2,)),
-    (Trapezoid1DKernel, (2,)),
-]
+
 
 NUMS = [1, 1.0, np.float32(1.0), np.float64(1.0)]
 
@@ -635,11 +622,26 @@ def test_kernel2d_initialization(self):
         with pytest.raises(TypeError):
             Kernel2D()
 
-    @pytest.mark.parametrize(["kernel", "opt"], KERNEL_TYPES_WITH_ARGS)
+    @pytest.mark.parametrize(
+        ["kernel", "opt"],
+        [
+            (AiryDisk2DKernel, (2,)),
+            (Box2DKernel, (2,)),
+            (Gaussian1DKernel, (2,)),
+            (Gaussian2DKernel, (2,)),
+            (RickerWavelet1DKernel, (2,)),
+            (RickerWavelet2DKernel, (2,)),
+            (Model1DKernel, (Gaussian1D(1, 0, 2),)),
+            (Model2DKernel, (Gaussian2D(1, 0, 0, 2, 2),)),
+            (Ring2DKernel, (9, 8)),
+            (Tophat2DKernel, (2,)),
+            (Trapezoid1DKernel, (2,)),
+        ],
+    )
     def test_array_keyword_not_allowed(self, kernel, opt):
         """
         Regression test for issue #10439
         """
         x = np.ones([10, 10])
-        with pytest.raises(TypeError, match=r".* allowed .*"):
+        with pytest.raises(TypeError, match=r"Array argument not allowed for kernel.*"):
             kernel(*opt, array=x)
diff --git a/astropy/coordinates/tests/test_angles.py b/astropy/coordinates/tests/test_angles.py
index 29bb9a9de5af..ca4b6de558cb 100644
--- a/astropy/coordinates/tests/test_angles.py
+++ b/astropy/coordinates/tests/test_angles.py
@@ -744,7 +744,6 @@ def test_latitude():
     ):
         Latitude(lon)
 
-    lon = Longitude(10, "deg")
     lat = Latitude([20], "deg")
     with pytest.raises(
         TypeError, match="A Longitude angle cannot be assigned to a Latitude angle"
diff --git a/astropy/cosmology/flrw/tests/conftest.py b/astropy/cosmology/flrw/tests/conftest.py
index 9fd0898aa721..96faace494a3 100644
--- a/astropy/cosmology/flrw/tests/conftest.py
+++ b/astropy/cosmology/flrw/tests/conftest.py
@@ -4,8 +4,12 @@
 
 from __future__ import annotations
 
+import copy
 from typing import TYPE_CHECKING, TypeVar
 
+import pytest
+
+from astropy.cosmology import core
 from astropy.cosmology.tests.helper import clean_registry  # noqa: F401
 from astropy.tests.helper import pickle_protocol  # noqa: F401
 
@@ -34,3 +38,11 @@ def filter_keys_from_items(
         Iterable of ``(key, value)`` pairs with the ``filter_out`` keys removed.
     """
     return ((k, v) for k, v in m.items() if k not in filter_out)
+
+
+@pytest.fixture
+def clean_cosmology_classes():
+    original = copy.deepcopy(core._COSMOLOGY_CLASSES)
+    yield
+    core._COSMOLOGY_CLASSES.clear()
+    core._COSMOLOGY_CLASSES.update(original)
diff --git a/astropy/cosmology/flrw/tests/test_base.py b/astropy/cosmology/flrw/tests/test_base.py
index eb891d3e1c46..c4f85b8ffe9f 100644
--- a/astropy/cosmology/flrw/tests/test_base.py
+++ b/astropy/cosmology/flrw/tests/test_base.py
@@ -1009,6 +1009,7 @@ def setup_class(self):
     # ---------------------------------------------------------------
     # class-level
 
+    @pytest.mark.usefixtures("clean_cosmology_classes")
     def test_init_subclass(self, cosmo_cls):
         """Test initializing subclass, mostly that can't have Ode0 in init."""
         super().test_init_subclass(cosmo_cls)
@@ -1019,11 +1020,6 @@ class HASOde0SubClass(cosmo_cls):
                 def __init__(self, Ode0):
                     pass
 
-        try:
-            _COSMOLOGY_CLASSES.pop(HASOde0SubClass.__qualname__, None)
-        except UnboundLocalError:
-            pass
-
     # ---------------------------------------------------------------
     # instance-level
 
diff --git a/astropy/io/ascii/tests/test_c_reader.py b/astropy/io/ascii/tests/test_c_reader.py
index ce3a765180e4..951c69e478d6 100644
--- a/astropy/io/ascii/tests/test_c_reader.py
+++ b/astropy/io/ascii/tests/test_c_reader.py
@@ -866,25 +866,16 @@ def test_rdb(read_rdb):
     assert table["B"].dtype.kind in ("S", "U")
     assert_equal(table["C"].dtype.kind, "f")
 
-    text = "A\tB\tC\nN\tS\tN\n4\tb\ta"  # C column contains non-numeric data
     with pytest.raises(ValueError) as e:
-        read_rdb(
-            text,
-        )
+        read_rdb("A\tB\tC\nN\tS\tN\n4\tb\ta")  # C column contains non-numeric data
     assert "Column C failed to convert" in str(e.value)
 
-    text = "A\tB\tC\nN\tN\n1\t2\t3"  # not enough types specified
     with pytest.raises(ValueError) as e:
-        read_rdb(
-            text,
-        )
+        read_rdb("A\tB\tC\nN\tN\n1\t2\t3")  # not enough types specified
     assert "mismatch between number of column names and column types" in str(e.value)
 
-    text = "A\tB\tC\nN\tN\t5\n1\t2\t3"  # invalid type for column C
     with pytest.raises(ValueError) as e:
-        read_rdb(
-            text,
-        )
+        read_rdb("A\tB\tC\nN\tN\t5\n1\t2\t3")  # invalid type for column C
     assert "type definitions do not all match [num](N|S)" in str(e.value)
 
 
diff --git a/astropy/io/fits/scripts/fitscheck.py b/astropy/io/fits/scripts/fitscheck.py
index 82acefcf98fb..62f3ec87da00 100644
--- a/astropy/io/fits/scripts/fitscheck.py
+++ b/astropy/io/fits/scripts/fitscheck.py
@@ -68,8 +68,7 @@ def handle_options(args):
         args = ["-h"]
 
     parser = argparse.ArgumentParser(
-        description=DESCRIPTION,
-        formatter_class=argparse.RawDescriptionHelpFormatter,
+        description=DESCRIPTION, formatter_class=argparse.RawDescriptionHelpFormatter
     )
 
     parser.add_argument(
diff --git a/astropy/io/fits/scripts/fitsheader.py b/astropy/io/fits/scripts/fitsheader.py
index fe412e30d498..8d55a1975e1a 100644
--- a/astropy/io/fits/scripts/fitsheader.py
+++ b/astropy/io/fits/scripts/fitsheader.py
@@ -401,8 +401,7 @@ def print_headers_as_comparison(args):
 def main(args=None):
     """This is the main function called by the `fitsheader` script."""
     parser = argparse.ArgumentParser(
-        description=DESCRIPTION,
-        formatter_class=argparse.RawDescriptionHelpFormatter,
+        description=DESCRIPTION, formatter_class=argparse.RawDescriptionHelpFormatter
     )
 
     parser.add_argument(
diff --git a/astropy/io/fits/scripts/fitsinfo.py b/astropy/io/fits/scripts/fitsinfo.py
index 30127f6d6707..3d32f7b0daad 100644
--- a/astropy/io/fits/scripts/fitsinfo.py
+++ b/astropy/io/fits/scripts/fitsinfo.py
@@ -55,8 +55,7 @@ def fitsinfo(filename):
 def main(args=None):
     """The main function called by the `fitsinfo` script."""
     parser = argparse.ArgumentParser(
-        description=DESCRIPTION,
-        formatter_class=argparse.RawDescriptionHelpFormatter,
+        description=DESCRIPTION, formatter_class=argparse.RawDescriptionHelpFormatter
     )
     parser.add_argument(
         "--version", action="version", version=f"%(prog)s {__version__}"
diff --git a/astropy/io/fits/tests/test_core.py b/astropy/io/fits/tests/test_core.py
index 4a077dc8d843..d2d6da5734d4 100644
--- a/astropy/io/fits/tests/test_core.py
+++ b/astropy/io/fits/tests/test_core.py
@@ -643,30 +643,24 @@ def test_open_file_handle(self):
                 pass
 
         # Opening without explicitly specifying binary mode should fail
-        with (
-            pytest.raises(ValueError),
-            open(self.data("test0.fits")) as handle,
-            fits.open(handle) as _,
-        ):
-            pass
+        with open(self.data("test0.fits")) as handle:
+            with pytest.raises(ValueError):
+                with fits.open(handle) as _:
+                    pass
 
         # All of these read modes should fail
         for mode in ["r", "rt"]:
-            with (
-                pytest.raises(ValueError),
-                open(self.data("test0.fits"), mode=mode) as handle,
-                fits.open(handle) as _,
-            ):
-                pass
+            with open(self.data("test0.fits"), mode=mode) as handle:
+                with pytest.raises(ValueError):
+                    with fits.open(handle) as _:
+                        pass
 
         # These update or write modes should fail as well
         for mode in ["w", "wt", "w+", "wt+", "r+", "rt+", "a", "at", "a+", "at+"]:
-            with (
-                pytest.raises(ValueError),
-                open(self.temp("temp.fits"), mode=mode) as handle,
-                fits.open(handle) as _,
-            ):
-                pass
+            with open(self.temp("temp.fits"), mode=mode) as handle:
+                with pytest.raises(ValueError):
+                    with fits.open(handle) as _:
+                        pass
 
     def test_fits_file_handle_mode_combo(self):
         # This should work fine since no mode is given
@@ -680,12 +674,10 @@ def test_fits_file_handle_mode_combo(self):
                 pass
 
         # This should not work since the modes conflict
-        with (
-            pytest.raises(ValueError),
-            open(self.data("test0.fits"), "rb") as handle,
-            fits.open(handle, mode="ostream") as _,
-        ):
-            pass
+        with open(self.data("test0.fits"), "rb") as handle:
+            with pytest.raises(ValueError):
+                with fits.open(handle, mode="ostream") as _:
+                    pass
 
     def test_open_from_url(self):
         file_url = "file:///" + self.data("test0.fits").lstrip("/")
@@ -695,20 +687,13 @@ def test_open_from_url(self):
 
         # It will not be possible to write to a file that is from a URL object
         for mode in ("ostream", "append", "update"):
-            with (
-                pytest.raises(ValueError),
-                urllib.request.urlopen(file_url) as urlobj,
-                fits.open(urlobj, mode=mode) as _,
-            ):
-                pass
+            with urllib.request.urlopen(file_url) as urlobj:
+                with pytest.raises(ValueError):
+                    with fits.open(urlobj, mode=mode) as _:
+                        pass
 
     @pytest.mark.remote_data(source="astropy")
     def test_open_from_remote_url(self):
-        def open_from_remote_url(remote_url, mode):
-            with urllib.request.urlopen(remote_url) as urlobj:
-                with fits.open(urlobj, mode=mode) as fits_handle:
-                    assert len(fits_handle) == 1
-
         for dataurl in (conf.dataurl, conf.dataurl_mirror):
             remote_url = f"{dataurl}/allsky/allsky_rosat.fits"
             try:
@@ -717,8 +702,10 @@ def open_from_remote_url(remote_url, mode):
                         assert len(fits_handle) == 1
 
                 for mode in ("ostream", "append", "update"):
-                    with pytest.raises(ValueError):
-                        open_from_remote_url(remote_url, mode)
+                    with urllib.request.urlopen(remote_url) as urlobj:
+                        with pytest.raises(ValueError):
+                            with fits.open(urlobj, mode=mode) as fits_handle:
+                                assert len(fits_handle) == 1
 
             except (urllib.error.HTTPError, urllib.error.URLError):
                 continue
diff --git a/astropy/io/fits/tests/test_fitscheck.py b/astropy/io/fits/tests/test_fitscheck.py
index 614b342b1f77..dd7e27cbb857 100644
--- a/astropy/io/fits/tests/test_fitscheck.py
+++ b/astropy/io/fits/tests/test_fitscheck.py
@@ -21,15 +21,12 @@ def test_help(self):
 
     def test_version(self, capsys):
         script = "fitscheck"
-        p = subprocess.Popen(
-            [script, "--version"],
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
+        script_result = subprocess.run(
+            [script, "--version"], capture_output=True, text=True, check=False
         )
-        stdout, stderr = p.communicate()
 
-        assert p.returncode == 0
-        assert stdout.decode("utf-8").strip() == f"fitscheck {version}"
+        assert script_result.returncode == 0
+        assert script_result.stdout.strip() == f"{script} {version}"
 
     def test_missing_file(self, capsys):
         assert fitscheck.main(["missing.fits"]) == 1
diff --git a/astropy/io/fits/tests/test_fitsdiff.py b/astropy/io/fits/tests/test_fitsdiff.py
index 15c58cc88b17..e914ac80e4e3 100644
--- a/astropy/io/fits/tests/test_fitsdiff.py
+++ b/astropy/io/fits/tests/test_fitsdiff.py
@@ -25,15 +25,12 @@ def test_help(self):
 
     def test_version(self, capsys):
         script = "fitsdiff"
-        p = subprocess.Popen(
-            [script, "--version"],
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
+        script_result = subprocess.run(
+            [script, "--version"], capture_output=True, text=True, check=False
         )
-        stdout, stderr = p.communicate()
 
-        assert p.returncode == 0
-        assert stdout.decode("utf-8").strip() == f"fitsdiff {version}"
+        assert script_result.returncode == 0
+        assert script_result.stdout.strip() == f"{script} {version}"
 
     def test_noargs(self):
         with pytest.raises(SystemExit) as e:
diff --git a/astropy/io/fits/tests/test_fitsheader.py b/astropy/io/fits/tests/test_fitsheader.py
index 7f3210eba1c9..ae4002fb38c6 100644
--- a/astropy/io/fits/tests/test_fitsheader.py
+++ b/astropy/io/fits/tests/test_fitsheader.py
@@ -18,15 +18,12 @@ def test_help(self):
 
     def test_version(self, capsys):
         script = "fitsheader"
-        p = subprocess.Popen(
-            [script, "--version"],
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
+        script_result = subprocess.run(
+            [script, "--version"], capture_output=True, text=True, check=False
         )
-        stdout, stderr = p.communicate()
 
-        assert p.returncode == 0
-        assert stdout.decode("utf-8").strip() == f"fitsheader {version}"
+        assert script_result.returncode == 0
+        assert script_result.stdout.strip() == f"{script} {version}"
 
     def test_file_exists(self, capsys):
         fitsheader.main([self.data("arange.fits")])
diff --git a/astropy/io/fits/tests/test_fitsinfo.py b/astropy/io/fits/tests/test_fitsinfo.py
index 8e6a18bfcfae..14390791db1c 100644
--- a/astropy/io/fits/tests/test_fitsinfo.py
+++ b/astropy/io/fits/tests/test_fitsinfo.py
@@ -18,15 +18,12 @@ def test_help(self):
 
     def test_version(self, capsys):
         script = "fitsinfo"
-        p = subprocess.Popen(
-            [script, "--version"],
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
+        script_result = subprocess.run(
+            [script, "--version"], capture_output=True, text=True, check=False
         )
-        stdout, stderr = p.communicate()
 
-        assert p.returncode == 0
-        assert stdout.decode("utf-8").strip() == f"fitsinfo {version}"
+        assert script_result.returncode == 0
+        assert script_result.stdout.strip() == f"{script} {version}"
 
     def test_onefile(self, capsys):
         fitsinfo.main([self.data("arange.fits")])
diff --git a/astropy/io/fits/tests/test_fitstime.py b/astropy/io/fits/tests/test_fitstime.py
index eb28e2ce4e86..457776d70615 100644
--- a/astropy/io/fits/tests/test_fitstime.py
+++ b/astropy/io/fits/tests/test_fitstime.py
@@ -93,9 +93,10 @@ def test_time_to_fits_loc(self, table_types):
             self.time, format="isot", scale="tt", location=EarthLocation(2, 3, 4)
         )
 
-        with pytest.raises(ValueError) as err:
+        with pytest.raises(
+            ValueError, match="Multiple Time Columns with different geocentric"
+        ):
             table, hdr = time_to_fits(t)
-        assert "Multiple Time Columns with different geocentric" in str(err.value)
 
         # Check that Time column with no location specified will assume global location
         t["b"] = Time(self.time, format="isot", scale="tt", location=None)
diff --git a/astropy/uncertainty/tests/test_distribution.py b/astropy/uncertainty/tests/test_distribution.py
index 2d5e1a40de39..7d48e10b1634 100644
--- a/astropy/uncertainty/tests/test_distribution.py
+++ b/astropy/uncertainty/tests/test_distribution.py
@@ -317,8 +317,7 @@ def test_reprs():
     ],
 )
 def test_wrong_kw_fails(func, kws):
-    kw_temp = kws.copy()
-    kw_temp["n_sample"] = 100  # note the missing "s"
+    kw_temp = kws | {"n_sample": 100}  # note the missing "s"
     with pytest.raises(TypeError, match="missing 1 required"):
         assert func(**kw_temp).n_samples == 100
     kw_temp = kws.copy()
diff --git a/astropy/units/tests/test_format.py b/astropy/units/tests/test_format.py
index 996ab0b7f7d5..c0de4603b760 100644
--- a/astropy/units/tests/test_format.py
+++ b/astropy/units/tests/test_format.py
@@ -48,7 +48,6 @@ def test_unit_grammar(strings, unit):
     "string", ["sin( /pixel /s)", "mag(mag)", "dB(dB(mW))", "dex()"]
 )
 def test_unit_grammar_fail(string):
-    string.__repr__()
     with pytest.raises(ValueError):
         u_format.Generic.parse(string)
 
@@ -131,7 +130,6 @@ def test_cds_grammar(strings, unit):
     ],
 )
 def test_cds_grammar_fail(string):
-    string.__repr__()
     with pytest.raises(ValueError):
         u_format.CDS.parse(string)
 
@@ -236,7 +234,6 @@ def test_ogip_grammar(strings, unit):
     ],
 )
 def test_ogip_grammar_fail(string):
-    string.__repr__()
     with pytest.raises(ValueError):
         u_format.OGIP.parse(string)
 
@@ -647,7 +644,6 @@ def test_deprecated_did_you_mean_units():
 @pytest.mark.parametrize("string", ["mag(ct/s)", "dB(mW)", "dex(cm s**-2)"])
 def test_fits_function(string):
     # Function units cannot be written, so ensure they're not parsed either.
-    string.__repr__()
     with pytest.raises(ValueError):
         u_format.Fits().parse(string)
 
@@ -655,10 +651,11 @@ def test_fits_function(string):
 @pytest.mark.parametrize("string", ["mag(ct/s)", "dB(mW)", "dex(cm s**-2)"])
 def test_vounit_function(string):
     # Function units cannot be written, so ensure they're not parsed either.
-    with pytest.raises(ValueError), warnings.catch_warnings():  # noqa: PT012
+    with warnings.catch_warnings():
         # ct, dex also raise warnings - irrelevant here.
         warnings.simplefilter("ignore")
-        u_format.VOUnit().parse(string)
+        with pytest.raises(ValueError):
+            u_format.VOUnit().parse(string)
 
 
 def test_vounit_binary_prefix():
diff --git a/astropy/wcs/tests/test_wcs.py b/astropy/wcs/tests/test_wcs.py
index a736b86c2285..f0ed1ce31a21 100644
--- a/astropy/wcs/tests/test_wcs.py
+++ b/astropy/wcs/tests/test_wcs.py
@@ -794,13 +794,10 @@ def test_error_message():
     hdr["PV2_1"] = -110
     hdr["PV2_2"] = -110
 
-    def init_wcs_and_alter(hdr):
+    with pytest.warns(wcs.FITSFixedWarning):
         w = wcs.WCS(hdr, _do_set=False)
-        w.all_pix2world([[536.0, 894.0]], 0)
-
-    with pytest.raises(wcs.InvalidTransformError):
-        with pytest.warns(wcs.FITSFixedWarning):
-            init_wcs_and_alter(hdr)
+        with pytest.raises(wcs.InvalidTransformError):
+            w.all_pix2world([[536.0, 894.0]], 0)
 
 
 def test_out_of_bounds():