diff --git a/tests/test_constrainobjects.py b/tests/test_constrainobjects.py
new file mode 100644
index 00000000..dcbeb93e
--- /dev/null
+++ b/tests/test_constrainobjects.py
@@ -0,0 +1,244 @@
+import numpy
+import numpy.random
+import numpy.testing
+import pytest
+import cellprofiler.object
+
+import constrainobjects
+
+
+instance = constrainobjects.ConstrainObjects
+
+
+@pytest.fixture(scope="function")
+def reference_empty():
+    obj = cellprofiler.object.Objects()
+
+    return obj
+
+
+@pytest.fixture(scope="function")
+def object_set_empty(objects_empty, reference_empty):
+    objects_set = cellprofiler.object.ObjectSet()
+    objects_set.add_objects(objects_empty, "InputObjects")
+    objects_set.add_objects(reference_empty, "ReferenceObjects")
+
+    return objects_set
+
+
+@pytest.fixture(scope="function")
+def image_labels():
+    labels = numpy.zeros((20, 20), dtype=numpy.uint16)
+
+    # Make some child objects
+    labels[2:7, 2:7] = 1
+    labels[2:7, 14:19] = 2
+    labels[14:19, 2:7] = 3
+    labels[14:20, 14:20] = 4
+    # One protruding object
+    labels[9:13, 9:13] = 5
+
+    return labels
+
+
+@pytest.fixture(scope="function")
+def image_reference():
+    labels = numpy.zeros((20, 20), dtype=numpy.uint16)
+
+    # Make some parent objects
+    labels[1:8, 1:8] = 1
+    labels[1:8, 13:20] = 2
+    labels[13:20, 1:8] = 3
+    labels[10:18, 10:18] = 4
+
+    return labels
+
+
+def test_2d_ignore(image_labels, image_reference, module, object_set_empty, objects_empty,
+                   reference_empty, workspace_empty):
+    labels = image_labels.copy()
+    reference = image_reference.copy()
+
+    objects_empty.segmented = labels
+    reference_empty.segmented = reference
+
+    module.x_name.value = "InputObjects"
+    module.y_name.value = "OutputObjects"
+    module.reference_name.value = "ReferenceObjects"
+
+    module.run(workspace_empty)
+
+    actual = object_set_empty.get_objects("OutputObjects").segmented
+
+    expected = labels.copy()
+    # The piece of object 4 outside of the parent should be removed
+    # and object 5 should be ignored
+    expected[14:20, 18:20] = 0
+    expected[18:20, 14:20] = 0
+
+    numpy.testing.assert_array_equal(actual, expected)
+
+
+def test_2d_remove_protrude(image_labels, image_reference, module, object_set_empty, objects_empty,
+                            reference_empty, workspace_empty):
+    labels = image_labels.copy()
+    reference = image_reference.copy()
+
+    objects_empty.segmented = labels
+    reference_empty.segmented = reference
+
+    module.x_name.value = "InputObjects"
+    module.y_name.value = "OutputObjects"
+    module.reference_name.value = "ReferenceObjects"
+
+    module.coersion_method.value = constrainobjects.METHOD_REMOVE
+
+    module.run(workspace_empty)
+
+    actual = object_set_empty.get_objects("OutputObjects").segmented
+
+    expected = labels.copy()
+    # The piece of object 4 outside of the parent should be removed
+    # and the part of object 5 inside object 4 should be removed
+    expected[14:20, 18:20] = 0
+    expected[18:20, 14:20] = 0
+    expected[10:13, 10:13] = 0
+
+    numpy.testing.assert_array_equal(actual, expected)
+
+
+def test_2d_remove_orphans(image_labels, image_reference, module, object_set_empty, objects_empty,
+                            reference_empty, workspace_empty):
+    labels = image_labels.copy()
+    reference = image_reference.copy()
+
+    objects_empty.segmented = labels
+    reference_empty.segmented = reference
+
+    module.x_name.value = "InputObjects"
+    module.y_name.value = "OutputObjects"
+    module.reference_name.value = "ReferenceObjects"
+
+    module.remove_orphans.value = True
+
+    module.run(workspace_empty)
+
+    actual = object_set_empty.get_objects("OutputObjects").segmented
+
+    expected = labels.copy()
+    # The piece of object 4 outside of the parent should be removed
+    expected[14:20, 18:20] = 0
+    expected[18:20, 14:20] = 0
+    # Object 5 should be removed altogether
+    expected[expected == 5] = 0
+
+    numpy.testing.assert_array_equal(actual, expected)
+
+
+@pytest.fixture(scope="function")
+def volume_labels():
+    labels = numpy.zeros((10, 20, 20), dtype=numpy.uint16)
+
+    # Make some child objects
+    labels[2:7, 2:7, 2:7] = 1
+    labels[2:5, 2:7, 14:19] = 2
+    labels[5:9, 14:19, 2:7] = 3
+    labels[3:8, 14:20, 14:20] = 4
+    # One protruding object
+    labels[0:9, 9:13, 9:13] = 5
+
+    return labels
+
+
+@pytest.fixture(scope="function")
+def volume_reference():
+    labels = numpy.zeros((10, 20, 20), dtype=numpy.uint16)
+
+    # Make some parent objects
+    labels[2:7, 1:8, 1:8] = 1
+    labels[2:5, 1:8, 13:20] = 2
+    labels[5:9, 13:20, 1:8] = 3
+    labels[3:8, 10:18, 10:18] = 4
+
+    return labels
+
+
+def test_3d_ignore(volume_labels, volume_reference, module, object_set_empty, objects_empty,
+                   reference_empty, workspace_empty):
+    labels = volume_labels.copy()
+    reference = volume_reference.copy()
+
+    objects_empty.segmented = labels
+    reference_empty.segmented = reference
+
+    module.x_name.value = "InputObjects"
+    module.y_name.value = "OutputObjects"
+    module.reference_name.value = "ReferenceObjects"
+
+    module.run(workspace_empty)
+
+    actual = object_set_empty.get_objects("OutputObjects").segmented
+
+    expected = labels.copy()
+    # The piece of object 4 outside of the parent should be removed
+    # and object 5 should be ignored
+    expected[3:8, 14:20, 18:20] = 0
+    expected[3:8, 18:20, 14:20] = 0
+
+    numpy.testing.assert_array_equal(actual, expected)
+
+
+def test_3d_remove_protrude(volume_labels, volume_reference, module, object_set_empty, objects_empty,
+                            reference_empty, workspace_empty):
+    labels = volume_labels.copy()
+    reference = volume_reference.copy()
+
+    objects_empty.segmented = labels
+    reference_empty.segmented = reference
+
+    module.x_name.value = "InputObjects"
+    module.y_name.value = "OutputObjects"
+    module.reference_name.value = "ReferenceObjects"
+
+    module.coersion_method.value = constrainobjects.METHOD_REMOVE
+
+    module.run(workspace_empty)
+
+    actual = object_set_empty.get_objects("OutputObjects").segmented
+
+    expected = labels.copy()
+    # The piece of object 4 outside of the parent should be removed
+    # and the part of object 5 inside object 4 should be removed
+    expected[3:8, 14:20, 18:20] = 0
+    expected[3:8, 18:20, 14:20] = 0
+    expected[3:8, 10:13, 10:13] = 0
+
+    numpy.testing.assert_array_equal(actual, expected)
+
+
+def test_3d_remove_orphans(volume_labels, volume_reference, module, object_set_empty, objects_empty,
+                           reference_empty, workspace_empty):
+    labels = volume_labels.copy()
+    reference = volume_reference.copy()
+
+    objects_empty.segmented = labels
+    reference_empty.segmented = reference
+
+    module.x_name.value = "InputObjects"
+    module.y_name.value = "OutputObjects"
+    module.reference_name.value = "ReferenceObjects"
+
+    module.remove_orphans.value = True
+
+    module.run(workspace_empty)
+
+    actual = object_set_empty.get_objects("OutputObjects").segmented
+
+    expected = labels.copy()
+    # The piece of object 4 outside of the parent should be removed
+    expected[3:8, 14:20, 18:20] = 0
+    expected[3:8, 18:20, 14:20] = 0
+    # Object 5 should be removed altogether
+    expected[expected == 5] = 0
+
+    numpy.testing.assert_array_equal(actual, expected)