diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 485fc08f5..7de90d9f5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -81,6 +81,8 @@ jobs:
         - linux: py39-devdeps-parallel
         - linux: py310-devdeps-parallel
         - linux: py311-devdeps-parallel
+        - linux: py312-devdeps-parallel
+          python-version: '3.12-dev'
 
   oldest:
     needs: [core, asdf-schemas]
diff --git a/asdf/_tests/tags/core/tests/test_ndarray.py b/asdf/_tests/tags/core/tests/test_ndarray.py
index 45373326f..941c6a125 100644
--- a/asdf/_tests/tags/core/tests/test_ndarray.py
+++ b/asdf/_tests/tags/core/tests/test_ndarray.py
@@ -241,12 +241,39 @@ def test_table_inline(tmpdir):
 
 
 def test_array_inline_threshold_recursive(tmpdir):
-    models = pytest.importorskip("astropy.modeling.models")
+    """
+    Test that setting the inline threshold works for objects
+    that contain (and when serialized produce a ndarray)
+    """
+
+    class NDArrayContainer:
+        def __init__(self, array):
+            self._array = array
+
+        @property
+        def array(self):
+            return np.array(self._array)
+
+    class NDArrayContainerConverter:
+        tags = ["http://somewhere.org/tags/foo-1.0.0"]
+        types = [NDArrayContainer]
+
+        def to_yaml_tree(self, obj, tag, ctx):
+            return {"array": obj.array}
+
+        def from_yaml_tree(self, node, tag, ctx):
+            return NDArrayContainer(node["array"])
+
+    class NDArrayContainerExtension:
+        tags = NDArrayContainerConverter.tags
+        converters = [NDArrayContainerConverter()]
+        extension_uri = "http://somewhere.org/extensions/foo-1.0.0"
 
-    aff = models.AffineTransformation2D(matrix=[[1, 2], [3, 4]])
-    tree = {"test": aff}
+    container = NDArrayContainer([[1, 2], [3, 4]])
+    tree = {"test": container}
 
     with asdf.config_context() as config:
+        config.add_extension(NDArrayContainerExtension())
         config.array_inline_threshold = 100
         # we can no longer use _helpers.assert_roundtrip_tree here because
         # the model no longer has a CustomType which results in equality testing
diff --git a/asdf/_tests/test_api.py b/asdf/_tests/test_api.py
index 3d394ce6f..0c5b8a575 100644
--- a/asdf/_tests/test_api.py
+++ b/asdf/_tests/test_api.py
@@ -7,7 +7,6 @@
 
 import numpy as np
 import pytest
-from astropy.modeling import models
 from numpy.testing import assert_array_equal
 
 import asdf
@@ -117,23 +116,6 @@ def test_atomic_write(tmp_path, small_tree):
         ff.write_to(tmpfile)
 
 
-def test_overwrite(tmp_path):
-    """
-    This is intended to reproduce the following issue:
-    https://github.com/asdf-format/asdf/issues/100
-    """
-    tmpfile = str(tmp_path / "test.asdf")
-    aff = models.AffineTransformation2D(matrix=[[1, 2], [3, 4]])
-    f = asdf.AsdfFile()
-    f.tree["model"] = aff
-    f.write_to(tmpfile)
-    model = f.tree["model"]
-
-    ff = asdf.AsdfFile()
-    ff.tree["model"] = model
-    ff.write_to(tmpfile)
-
-
 def test_default_version():
     """
     See https://github.com/asdf-format/asdf/issues/364
diff --git a/asdf/_tests/test_asdf.py b/asdf/_tests/test_asdf.py
index d41e2b31a..8584367d8 100644
--- a/asdf/_tests/test_asdf.py
+++ b/asdf/_tests/test_asdf.py
@@ -1,6 +1,5 @@
 import os
 
-import fsspec
 import pytest
 
 from asdf import config_context
@@ -361,6 +360,8 @@ def test_fsspec(tmp_path):
     Issue #1146 reported errors when opening a fsspec 'file'
     This is a regression test for the fix in PR #1226
     """
+    fsspec = pytest.importorskip("fsspec")
+
     tree = {"a": 1}
     af = AsdfFile(tree)
     fn = tmp_path / "test.asdf"
@@ -378,6 +379,8 @@ def test_fsspec_http(httpserver):
     filesystem)
     This is a regression test for the fix in PR #1228
     """
+    fsspec = pytest.importorskip("fsspec")
+
     tree = {"a": 1}
     af = AsdfFile(tree)
     path = os.path.join(httpserver.tmpdir, "test")
diff --git a/asdf/_tests/test_file_format.py b/asdf/_tests/test_file_format.py
index 6c9cc593b..6a82671a6 100644
--- a/asdf/_tests/test_file_format.py
+++ b/asdf/_tests/test_file_format.py
@@ -59,7 +59,6 @@ def test_no_final_newline(tmp_path):
         assert len(ff.tree) == 2
 
 
-@pytest.mark.filterwarnings("ignore::astropy.io.fits.verify.VerifyWarning")
 def test_no_asdf_header(tmp_path):
     content = b"What? This ain't no ASDF file"
 
@@ -98,7 +97,6 @@ def test_empty_file():
         assert len(ff._blocks.blocks) == 0
 
 
-@pytest.mark.filterwarnings("ignore::astropy.io.fits.verify.VerifyWarning")
 @pytest.mark.filterwarnings("ignore::asdf.exceptions.AsdfDeprecationWarning")
 def test_not_asdf_file():
     buff = io.BytesIO(b"SIMPLE")
diff --git a/asdf/_tests/test_generic_io.py b/asdf/_tests/test_generic_io.py
index fbc8427cc..b92047b00 100644
--- a/asdf/_tests/test_generic_io.py
+++ b/asdf/_tests/test_generic_io.py
@@ -5,7 +5,6 @@
 import sys
 import urllib.request as urllib_request
 
-import fsspec
 import numpy as np
 import pytest
 
@@ -786,6 +785,8 @@ def test_fsspec(tmp_path):
     Issue #1146 reported errors when opening a fsspec 'file'
     This is a regression test for the fix in PR #1226
     """
+    fsspec = pytest.importorskip("fsspec")
+
     ref = b"01234567890"
     fn = tmp_path / "test"
 
@@ -809,6 +810,8 @@ def test_fsspec_http(httpserver):
     filesystem)
     This is a regression test for the fix in PR #1228
     """
+    fsspec = pytest.importorskip("fsspec")
+
     ref = b"01234567890"
     path = os.path.join(httpserver.tmpdir, "test")
 
diff --git a/asdf/_tests/test_schema.py b/asdf/_tests/test_schema.py
index 7496d5bbb..82cea9238 100644
--- a/asdf/_tests/test_schema.py
+++ b/asdf/_tests/test_schema.py
@@ -64,22 +64,43 @@ class TagReferenceExtension:
 
 
 def test_tagging_scalars():
-    pytest.importorskip("astropy", "3.0.0")
-    from astropy import units as u
+    class Scalar:
+        def __init__(self, value):
+            self.value = value
 
-    yaml = """
-unit: !unit/unit-1.0.0
+    scalar_tag = "http://somewhere.org/tags/scalar-1.0.0"
+
+    class ScalarConverter:
+        tags = [scalar_tag]
+        types = [Scalar]
+
+        def to_yaml_tree(self, obj, tag, ctx):
+            return obj.value
+
+        def from_yaml_tree(self, node, tag, ctx):
+            return Scalar(node)
+
+    class ScalarExtension:
+        tags = [scalar_tag]
+        converters = [ScalarConverter()]
+        extension_uri = "http://somewhere.org/extensions/scalar-1.0.0"
+
+    yaml = f"""
+tagged: !<{scalar_tag}>
   m
-not_unit:
+not_tagged:
   m
     """
-    buff = helpers.yaml_to_asdf(yaml)
-    with asdf.open(buff) as ff:
-        assert isinstance(ff.tree["unit"], u.UnitBase)
-        assert not isinstance(ff.tree["not_unit"], u.UnitBase)
-        assert isinstance(ff.tree["not_unit"], str)
+    with asdf.config_context() as cfg:
+        cfg.add_extension(ScalarExtension())
+        buff = helpers.yaml_to_asdf(yaml)
+        with asdf.open(buff) as ff:
+            assert isinstance(ff.tree["tagged"], Scalar)
+            assert not isinstance(ff.tree["not_tagged"], Scalar)
+            assert isinstance(ff.tree["not_tagged"], str)
 
-        assert ff.tree == {"unit": u.m, "not_unit": "m"}
+            assert ff.tree["tagged"].value == "m"
+            assert ff.tree["not_tagged"] == "m"
 
 
 def test_read_json_schema():
diff --git a/pyproject.toml b/pyproject.toml
index 1834068f4..3f954c247 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -43,14 +43,11 @@ docs = [
   'tomli; python_version < "3.11"',
 ]
 tests = [
-  "astropy>=5.0.4",
   "fsspec[http]>=2022.8.2",
-  "asdf-astropy>=0.4.0",
   "lz4>=0.10",
   "psutil",
   "pytest>=6",
   "pytest-doctestplus",
-  "pytest-openfiles",
   "pytest-remotedata",
 ]
 [project.urls]
@@ -107,15 +104,13 @@ minversion = 4.6
 norecursedirs = ['build', 'docs/_build', 'docs/sphinxext']
 doctest_plus = 'enabled'
 remote_data_strict = true
-# The asdf.asdftypes module emits a warning on import,
-# which pytest trips over during collection:
 filterwarnings = [
     'error',
     'ignore:numpy.ndarray size changed:RuntimeWarning',
 ]
 # Configuration for pytest-doctestplus
 text_file_format = 'rst'
-addopts = '--color=yes --doctest-rst'
+addopts = '--color=yes --doctest-rst -rsx'
 
 [tool.coverage.run]
 omit = [
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 82af43cfc..a552322cc 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,11 +1,12 @@
-git+https://github.com/astropy/asdf-astropy
 git+https://github.com/asdf-format/asdf-coordinates-schemas
 git+https://github.com/asdf-format/asdf-standard
 git+https://github.com/asdf-format/asdf-transform-schemas
 git+https://github.com/asdf-format/asdf-unit-schemas.git
 git+https://github.com/asdf-format/asdf-wcs-schemas
-git+https://github.com/astropy/astropy
-#git+https://github.com/yaml/pyyaml.git
+git+https://github.com/yaml/pyyaml.git
 
 numpy>=0.0.dev0
+# although we don't use scipy, we include it here so that any dependency
+# that uses it during these tests will use the development version
+# which is more likely to work with the above development version of numpy
 scipy>=0.0.dev0
diff --git a/tox.ini b/tox.ini
index 42c494872..87f88ce22 100644
--- a/tox.ini
+++ b/tox.ini
@@ -2,7 +2,8 @@
 env_list =
     compatibility
     coverage
-    py{39,310,311}{,-compatibility,-coverage,-jsonschema}{,-parallel}
+    devdep{,-parallel}
+    py{39,310,311,312}{,-compatibility,-coverage,-jsonschema}{,-parallel}
     asdf{-standard,-transform-schemas,-unit-schemas,-wcs-schemas,-coordinates-schemas,-astropy}
     gwcs
     jwst
@@ -46,7 +47,6 @@ commands =
     --remote-data \
     --durations=10 \
     jsonschema: --jsonschema \
-    coverage: --open-files \
     parallel: --numprocesses auto \
 # the OpenAstronomy workflow appends `--cov-report` in `{posargs}`, which `coverage` doesn't recognize
     !coverage: {posargs}