diff --git a/README.md b/README.md
index 016a5e5..57dc66a 100644
--- a/README.md
+++ b/README.md
@@ -69,7 +69,27 @@ assert registry.find("my_device") is the_device
 ```
 
 This greedy behavior can be suppressed with the *auto_register*
-parameter. If *auto_register* is false, then a device class can be
+parameter. It can also be turned off after initialization by setting
+the *auto_register* attribute to ``False``::
+
+```python
+
+registry = Registry(auto_register=False)
+
+# Make a bunch of devices
+...
+
+# Turn if off for this one
+registry.auto_register = False
+device = MyDevice(...)
+registry.auto_register = True
+
+# Register some other devices maybe
+...
+
+```
+
+If *auto_register* is false, then a device class can be
 decorated to allow the registry to find it:
 
 ```python
diff --git a/pyproject.toml b/pyproject.toml
index a35a671..9861a89 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -19,7 +19,7 @@ dependencies = ["ophyd"]
 
 [project.optional-dependencies]
 
-dev = ["black", "isort", "pytest", "build", "twine", "flake8", "caproto", "ruff"]
+dev = ["black", "isort", "pytest", "build", "twine", "flake8", "ruff"]
 
 [project.urls]
 "Homepage" = "https://github.com/spc-group/ophyd-registry"
diff --git a/src/ophydregistry/registry.py b/src/ophydregistry/registry.py
index 5b7239e..4ca7576 100644
--- a/src/ophydregistry/registry.py
+++ b/src/ophydregistry/registry.py
@@ -107,6 +107,7 @@ class Registry:
     """
 
     use_typhos: bool = False
+    _auto_register: bool
 
     # components: Sequence
     _objects_by_name: Mapping
@@ -119,11 +120,28 @@ def __init__(self, auto_register: bool = True, use_typhos: bool = False):
         # Set up empty lists and things for registering components
         self.clear()
         self.use_typhos = use_typhos
-        # Add a callback to get notified of new objects
-        if auto_register:
+        self.auto_register = auto_register
+
+    @property
+    def auto_register(self):
+        return self._auto_register
+
+    @auto_register.setter
+    def auto_register(self, val):
+        """Turn on or off the automatic registration of new devices."""
+        self._auto_register = val
+        if val:
+            # Add a callback to get notified of new objects
             ophydobj.OphydObject.add_instantiation_callback(
                 self.register, fail_if_late=False
             )
+        else:
+            try:
+                ophydobj.OphydObject._OphydObject__instantiation_callbacks.remove(
+                    self.register
+                )
+            except ValueError:
+                pass
 
     def __getitem__(self, key):
         """Retrieve the object from the dicionary.
@@ -454,11 +472,14 @@ def register(self, component: ophydobj.OphydObject) -> ophydobj.OphydObject:
             # (Needed for some sub-components that are just readback
             # values of the parent)
             # Check that we're not adding a duplicate component name
+            if name == "I0_center":
+                print(self._objects_by_name.keys(), self)
             if name in self._objects_by_name.keys():
                 old_obj = self._objects_by_name[name]
                 is_readback = component in [
                     getattr(old_obj, "readback", None),
                     getattr(old_obj, "user_readback", None),
+                    getattr(old_obj, "val", None),
                 ]
                 if is_readback:
                     msg = f"Ignoring readback with duplicate name: '{name}'"
diff --git a/src/ophydregistry/tests/test_instrument_registry.py b/src/ophydregistry/tests/test_instrument_registry.py
index e8feae6..86b2599 100644
--- a/src/ophydregistry/tests/test_instrument_registry.py
+++ b/src/ophydregistry/tests/test_instrument_registry.py
@@ -1,3 +1,4 @@
+import gc
 import logging
 
 import pytest
@@ -8,13 +9,14 @@
 
 @pytest.fixture()
 def registry():
-    reg = Registry(auto_register=False)
-    return reg
+    reg = Registry(auto_register=False, use_typhos=False)
+    try:
+        yield reg
+    finally:
+        del reg
 
 
 def test_register_component(registry):
-    # Prepare registry
-    registry = Registry(auto_register=False)
     # Create an unregistered component
     cpt = sim.SynGauss(
         "I0",
@@ -40,9 +42,8 @@ def test_register_component(registry):
     assert cpt in results
 
 
-def test_find_missing_components():
+def test_find_missing_components(registry):
     """Test that registry raises an exception if no matches are found."""
-    reg = Registry()
     cpt = sim.SynGauss(
         "I0",
         sim.motor,
@@ -52,25 +53,23 @@ def test_find_missing_components():
         sigma=1,
         labels={"ion_chamber"},
     )
-    reg.register(cpt)
+    registry.register(cpt)
     # Now make sure a different query still returns no results
     with pytest.raises(ComponentNotFound):
-        reg.findall(label="spam")
+        registry.findall(label="spam")
 
 
-def test_find_allow_missing_components():
+def test_find_allow_missing_components(registry):
     """Test that registry tolerates missing components with the
     *allow_none* argument.
 
     """
-    reg = Registry()
     # Get some non-existent devices and check that the right nothing is returned
-    assert list(reg.findall(label="spam", allow_none=True)) == []
-    assert reg.find(name="eggs", allow_none=True) is None
+    assert list(registry.findall(label="spam", allow_none=True)) == []
+    assert registry.find(name="eggs", allow_none=True) is None
 
 
 def test_exceptions(registry):
-    registry = Registry()
     registry.register(Device("", name="It"))
     # Test if a non-existent labels throws an exception
     with pytest.raises(ComponentNotFound):
@@ -137,9 +136,7 @@ def test_find_name_by_dot_notation(registry):
     assert result is cptA.val
 
 
-def test_find_labels_by_dot_notation():
-    # Prepare registry
-    reg = Registry()
+def test_find_labels_by_dot_notation(registry):
     # Create a simulated component
     cptA = sim.SynGauss(
         "I0",
@@ -150,15 +147,13 @@ def test_find_labels_by_dot_notation():
         sigma=1,
         labels={"ion_chamber"},
     )
-    reg.register(cptA)
+    registry.register(cptA)
     # Only one match should work fine
-    result = reg.find(label="ion_chamber.val")
+    result = registry.find(label="ion_chamber.val")
     assert result is cptA.val
 
 
-def test_find_any():
-    # Prepare registry
-    reg = Registry()
+def test_find_any(registry):
     # Create an unregistered component
     cptA = sim.SynGauss(
         "I0",
@@ -196,25 +191,23 @@ def test_find_any():
         labels={},
     )
     # Register the components
-    reg.register(cptA)
-    reg.register(cptB)
-    reg.register(cptC)
-    reg.register(cptD)
+    registry.register(cptA)
+    registry.register(cptB)
+    registry.register(cptC)
+    registry.register(cptD)
     # Only one match should work fine
-    result = reg.findall(any_of="ion_chamber")
+    result = registry.findall(any_of="ion_chamber")
     assert cptA in result
     assert cptB in result
     assert cptC in result
     assert cptD not in result
 
 
-def test_find_by_device():
+def test_find_by_device(registry):
     """The registry should just return the device itself if that's what is passed."""
-    # Prepare registry
-    reg = Registry()
     # Register a component
     cptD = sim.SynGauss(
-        "sample motor",
+        "sample_motor",
         sim.motor,
         "motor",
         center=-0.5,
@@ -222,16 +215,14 @@ def test_find_by_device():
         sigma=1,
         labels={},
     )
-    reg.register(cptD)
+    registry.register(cptD)
     # Pass the device itself to the find method
-    result = reg.find(cptD)
+    result = registry.find(cptD)
     assert result is cptD
 
 
-def test_find_by_list_of_names():
+def test_find_by_list_of_names(registry):
     """Will the findall() method handle lists of things to look up."""
-    # Prepare registry
-    reg = Registry()
     # Register a component
     cptA = sim.SynGauss(
         "sample motor A",
@@ -260,11 +251,11 @@ def test_find_by_list_of_names():
         sigma=1,
         labels={},
     )
-    reg.register(cptA)
-    reg.register(cptB)
-    reg.register(cptC)
+    registry.register(cptA)
+    registry.register(cptB)
+    registry.register(cptC)
     # Pass the device names into the findall method
-    result = reg.findall(["sample motor A", "sample motor B"])
+    result = registry.findall(["sample motor A", "sample motor B"])
     assert cptA in result
     assert cptB in result
     assert cptC not in result
@@ -272,7 +263,9 @@ def test_find_by_list_of_names():
 
 def test_user_readback(registry):
     """Edge case where EpicsMotor.user_readback is named the same as the motor itself."""
-    device = EpicsMotor("255idVME:m1", name="epics_motor")
+    device = sim.instantiate_fake_device(
+        EpicsMotor, prefix="255idVME:m1", name="epics_motor"
+    )
     registry.register(device)
     # See if requesting the device.user_readback returns the proper signal
     registry.find("epics_motor_user_readback")
@@ -284,7 +277,8 @@ def test_auto_register():
     Uses ophyds instantiation callback mechanism.
 
     """
-    registry = Registry()
+    registry = Registry(auto_register=True)
+    print(f"auto_register: {registry}")
     sim.SynGauss(
         "I0",
         sim.motor,
@@ -295,11 +289,12 @@ def test_auto_register():
         labels={"ion_chamber"},
     )
     registry.find("I0")
+    # Delete this registry to avoid warnings about duplicate entries
+    registry.auto_register = False
 
 
-def test_clear():
+def test_clear(registry):
     """Can the registry be properly cleared."""
-    registry = Registry()
     cpt = sim.SynGauss(
         "I0",
         sim.motor,
@@ -309,6 +304,7 @@ def test_clear():
         sigma=1,
         labels={"ion_chamber"},
     )
+    registry.register(cpt)
     assert registry.find("I0") is cpt
     # Clear the registry and confirm that it's gone
     registry.clear()
@@ -316,10 +312,10 @@ def test_clear():
         registry.find("I0")
 
 
-def test_component_properties():
+def test_component_properties(registry):
     """Check that we can get lists of component and devices."""
-    registry = Registry()
-    sim.SynGauss(
+    print(f"component_properties: {registry}")
+    I0 = sim.SynGauss(
         "I0",
         sim.motor,
         "motor",
@@ -328,6 +324,7 @@ def test_component_properties():
         sigma=1,
         labels={"ion_chamber"},
     )
+    registry.register(I0)
     assert registry.device_names == {"I0"}
     assert registry.component_names == {
         "I0",
@@ -336,12 +333,10 @@ def test_component_properties():
         "I0_noise",
         "I0_noise_multiplier",
         "I0_sigma",
-        "I0_val",
     }
 
 
-def test_root_devices():
-    registry = Registry()
+def test_root_devices(registry):
     registry.register(sim.motor1)
     registry.register(sim.motor2)
     registry.register(sim.motor3)
@@ -350,18 +345,16 @@ def test_root_devices():
     assert len(root_devices) == 3
 
 
-def test_getitem():
+def test_getitem(registry):
     """Check that the registry can be accessed like a dictionary."""
-    registry = Registry()
     registry.register(sim.motor1)
     # Check that the dictionary access works
     result = registry["motor1"]
     assert result is sim.motor1
 
 
-def test_duplicate_device(caplog):
+def test_duplicate_device(caplog, registry):
     """Check that a device doesn't get added twice."""
-    registry = Registry()
     motor = sim.motor
     # Set up logging so that we can know what
     caplog.clear()
@@ -379,10 +372,9 @@ def test_duplicate_device(caplog):
     assert "Ignoring component with duplicate name" in caplog.text
 
 
-def test_delete_by_name():
+def test_delete_by_name(registry):
     """Check that we can remove an item from the ophyd registry."""
     # Add an item to the registry
-    registry = Registry()
     motor = sim.motor
     registry.register(motor)
     # Delete the item from the registry
@@ -392,10 +384,9 @@ def test_delete_by_name():
         registry[motor.name]
 
 
-def test_pop_by_name():
+def test_pop_by_name(registry):
     """Check that we can remove an item from the ophyd registry."""
     # Add an item to the registry
-    registry = Registry()
     motor = sim.motor
     registry.register(motor)
     # Pop the item from the registry
@@ -411,10 +402,9 @@ def test_pop_by_name():
         registry[motor.acceleration.name]
 
 
-def test_pop_by_object():
+def test_pop_by_object(registry):
     """Check that we can remove an item from the ophyd registry."""
     # Add an item to the registry
-    registry = Registry()
     motor = sim.motor
     registry.register(motor)
     # Pop the item from the registry
@@ -427,10 +417,9 @@ def test_pop_by_object():
         registry["motors"]
 
 
-def test_pop_default():
+def test_pop_default(registry):
     """Check that we get a default object if our key is not present."""
     # Add an item to the registry
-    registry = Registry()
     motor = sim.motor
     # Pop the item from the registry
     popped = registry.pop("gibberish", motor)