diff --git a/asdf/_tests/tags/core/tests/test_ndarray.py b/asdf/_tests/tags/core/tests/test_ndarray.py
index 08a2202fe..d0f4b80ab 100644
--- a/asdf/_tests/tags/core/tests/test_ndarray.py
+++ b/asdf/_tests/tags/core/tests/test_ndarray.py
@@ -976,7 +976,7 @@ def test_memmap_write(tmp_path):
     tmpfile = str(tmp_path / "data.asdf")
     tree = {"data": np.zeros(100)}
 
-    with asdf.AsdfFile(tree) as af:
+    with asdf.AsdfFile(tree, memmap=False) as af:
         # Make sure we're actually writing to an internal array for this test
         af.write_to(tmpfile, all_array_storage="internal")
 
@@ -1002,7 +1002,7 @@ def test_readonly(tmp_path):
         af.write_to(tmpfile, all_array_storage="internal")
 
     # Opening in read mode (the default) should mean array is readonly
-    with asdf.open(tmpfile) as af:
+    with asdf.open(tmpfile, memmap=True) as af:
         assert af["data"].flags.writeable is False
         with pytest.raises(ValueError, match=r"assignment destination is read-only"):
             af["data"][0] = 41
@@ -1046,7 +1046,7 @@ def test_block_data_change(pad_blocks, tmp_path):
     with asdf.AsdfFile(tree) as af:
         af.write_to(tmpfile, pad_blocks=pad_blocks)
 
-    with asdf.open(tmpfile, mode="rw") as af:
+    with asdf.open(tmpfile, mode="rw", memmap=True) as af:
         assert np.all(af.tree["data"] == 0)
         array_before = af.tree["data"].__array__()
         af.tree["data"][:5] = 1
diff --git a/asdf/_tests/test_api.py b/asdf/_tests/test_api.py
index 2b95734f3..0819d2a08 100644
--- a/asdf/_tests/test_api.py
+++ b/asdf/_tests/test_api.py
@@ -61,7 +61,7 @@ def test_open_readonly(tmp_path):
     os.chmod(tmpfile, 0o440)
     assert os.access(tmpfile, os.W_OK) is False
 
-    with asdf.open(tmpfile) as af:
+    with asdf.open(tmpfile, memmap=True) as af:
         assert af["baz"].flags.writeable is False
 
     with pytest.raises(PermissionError, match=r".* Permission denied: .*"), asdf.open(tmpfile, mode="rw"):
diff --git a/asdf/_tests/test_array_blocks.py b/asdf/_tests/test_array_blocks.py
index e8d8cf3c4..e162e668d 100644
--- a/asdf/_tests/test_array_blocks.py
+++ b/asdf/_tests/test_array_blocks.py
@@ -811,9 +811,11 @@ def filename_with_array(tmp_path_factory):
 @pytest.mark.parametrize(
     "open_kwargs,should_memmap",
     [
-        ({}, True),
-        ({"memmap": True}, True),
-        ({"memmap": False}, False),
+        ({}, False),
+        ({"lazy_load": True, "memmap": True}, True),
+        ({"lazy_load": False, "memmap": True}, True),
+        ({"lazy_load": True, "memmap": False}, False),
+        ({"lazy_load": False, "memmap": False}, False),
     ],
 )
 def test_open_no_memmap(filename_with_array, open_kwargs, should_memmap):
@@ -823,7 +825,7 @@ def test_open_no_memmap(filename_with_array, open_kwargs, should_memmap):
         default (no kwargs)
         memmap
     """
-    with asdf.open(filename_with_array, lazy_load=False, **open_kwargs) as af:
+    with asdf.open(filename_with_array, **open_kwargs) as af:
         array = af.tree["array"]
         if should_memmap:
             assert isinstance(array.base, np.memmap)
diff --git a/asdf/_tests/test_generic_io.py b/asdf/_tests/test_generic_io.py
index fea00295f..25158b632 100644
--- a/asdf/_tests/test_generic_io.py
+++ b/asdf/_tests/test_generic_io.py
@@ -110,7 +110,7 @@ def get_read_fd():
         f.read(0)
         return f
 
-    with _roundtrip(tree, get_write_fd, get_read_fd) as ff:
+    with _roundtrip(tree, get_write_fd, get_read_fd, read_options={"memmap": True}) as ff:
         assert len(ff._blocks.blocks) == 2
         assert isinstance(ff._blocks.blocks[0].cached_data, np.memmap)
 
@@ -133,7 +133,7 @@ def get_read_fd():
         assert f._uri == path.as_uri()
         return f
 
-    with _roundtrip(tree, get_write_fd, get_read_fd) as ff:
+    with _roundtrip(tree, get_write_fd, get_read_fd, read_options={"memmap": True}) as ff:
         assert len(ff._blocks.blocks) == 2
         assert isinstance(ff._blocks.blocks[0].cached_data, np.memmap)
 
@@ -173,7 +173,7 @@ def get_read_fd():
         assert f._uri == path.as_uri()
         return f
 
-    with _roundtrip(tree, get_write_fd, get_read_fd) as ff:
+    with _roundtrip(tree, get_write_fd, get_read_fd, read_options={"memmap": True}) as ff:
         assert len(ff._blocks.blocks) == 2
         assert isinstance(ff._blocks.blocks[0].cached_data, np.memmap)
         ff.tree["science_data"][0] = 42
diff --git a/asdf/_tests/test_reference.py b/asdf/_tests/test_reference.py
index 8cbfb16b0..9fd3d38a8 100644
--- a/asdf/_tests/test_reference.py
+++ b/asdf/_tests/test_reference.py
@@ -79,7 +79,7 @@ def do_asserts(ff):
 
         assert_array_equal(ff.tree["internal"], exttree["cool_stuff"]["a"])
 
-    with asdf.AsdfFile({}, uri=(tmp_path / "main.asdf").as_uri()) as ff:
+    with asdf.AsdfFile({}, uri=(tmp_path / "main.asdf").as_uri(), memmap=True) as ff:
         # avoid passing tree to AsdfFile to avoid the deprecation warning, this can be updated
         # when automatic find_references on AsdfFile.__init__ is removed
         ff.tree = tree