diff --git a/armi/bookkeeping/db/tests/test_database3.py b/armi/bookkeeping/db/tests/test_database3.py
index c4e769ea9..91246ac57 100644
--- a/armi/bookkeeping/db/tests/test_database3.py
+++ b/armi/bookkeeping/db/tests/test_database3.py
@@ -29,8 +29,8 @@
 from armi.reactor.excoreStructure import ExcoreCollection, ExcoreStructure
 from armi.reactor.reactors import Core, Reactor
 from armi.reactor.spentFuelPool import SpentFuelPool
-from armi.reactor.tests.test_reactors import loadTestReactor, reduceTestReactorRings
 from armi.settings.fwSettings.globalSettings import CONF_SORT_REACTOR
+from armi.testing import loadTestReactor, reduceTestReactorRings
 from armi.tests import TEST_ROOT, mockRunLogs
 from armi.utils import getPreviousTimeNode, safeCopy
 from armi.utils.directoryChangers import TemporaryDirectoryChanger
diff --git a/armi/bookkeeping/db/tests/test_databaseInterface.py b/armi/bookkeeping/db/tests/test_databaseInterface.py
index e5d066553..a4c12ded4 100644
--- a/armi/bookkeeping/db/tests/test_databaseInterface.py
+++ b/armi/bookkeeping/db/tests/test_databaseInterface.py
@@ -29,7 +29,7 @@
 from armi.physics.neutronics.settings import CONF_LOADING_FILE
 from armi.reactor import grids
 from armi.reactor.flags import Flags
-from armi.reactor.tests.test_reactors import loadTestReactor, reduceTestReactorRings
+from armi.testing import loadTestReactor, reduceTestReactorRings
 from armi.tests import TEST_ROOT
 from armi.utils import directoryChangers
 
diff --git a/armi/bookkeeping/report/tests/test_report.py b/armi/bookkeeping/report/tests/test_report.py
index 24e0ac9b8..b395781d6 100644
--- a/armi/bookkeeping/report/tests/test_report.py
+++ b/armi/bookkeeping/report/tests/test_report.py
@@ -40,7 +40,7 @@
     writeCycleSummary,
     writeWelcomeHeaders,
 )
-from armi.reactor.tests.test_reactors import loadTestReactor
+from armi.testing import loadTestReactor
 from armi.tests import mockRunLogs
 from armi.utils.directoryChangers import TemporaryDirectoryChanger
 
diff --git a/armi/cli/tests/test_runEntryPoint.py b/armi/cli/tests/test_runEntryPoint.py
index 97fcacb3e..2094f6222 100644
--- a/armi/cli/tests/test_runEntryPoint.py
+++ b/armi/cli/tests/test_runEntryPoint.py
@@ -34,7 +34,7 @@
 from armi.cli.run import RunEntryPoint
 from armi.cli.runSuite import RunSuiteCommand
 from armi.physics.neutronics.diffIsotxs import CompareIsotxsLibraries
-from armi.reactor.tests.test_reactors import loadTestReactor, reduceTestReactorRings
+from armi.testing import loadTestReactor, reduceTestReactorRings
 from armi.tests import ARMI_RUN_PATH, TEST_ROOT, mockRunLogs
 from armi.utils.directoryChangers import TemporaryDirectoryChanger
 from armi.utils.dynamicImporter import getEntireFamilyTree
diff --git a/armi/context.py b/armi/context.py
index 76b9e5c02..8436ceae5 100644
--- a/armi/context.py
+++ b/armi/context.py
@@ -97,12 +97,7 @@ def setMode(cls, mode):
 
 
 try:
-    # Check for MPI. The mpi4py module uses cPickle to serialize python objects in preparation for
-    # network transmission. Sometimes, when cPickle fails, it gives very cryptic error messages that
-    # do not help much. If you uncomment th following line, you can trick mpi4py into using the
-    # pure-python pickle module in place of cPickle and now you will generally get much more
-    # meaningful and useful error messages Then comment it back out because it's slow.
-    # import sys, pickle; sys.modules['cPickle'] = pickle
+    # Check for MPI
     from mpi4py import MPI
 
     MPI_COMM = MPI.COMM_WORLD
diff --git a/armi/physics/neutronics/latticePhysics/tests/test_latticeWriter.py b/armi/physics/neutronics/latticePhysics/tests/test_latticeWriter.py
index 90c96accf..89f1b1225 100644
--- a/armi/physics/neutronics/latticePhysics/tests/test_latticeWriter.py
+++ b/armi/physics/neutronics/latticePhysics/tests/test_latticeWriter.py
@@ -30,7 +30,7 @@
     CONF_DISABLE_BLOCK_TYPE_EXCLUSION_IN_XS_GENERATION,
     CONF_XS_BLOCK_REPRESENTATION,
 )
-from armi.reactor.tests.test_reactors import loadTestReactor
+from armi.testing import loadTestReactor
 from armi.tests import TEST_ROOT
 
 
diff --git a/armi/physics/neutronics/tests/test_crossSectionTable.py b/armi/physics/neutronics/tests/test_crossSectionTable.py
index c0f23f7d0..a961be50e 100644
--- a/armi/physics/neutronics/tests/test_crossSectionTable.py
+++ b/armi/physics/neutronics/tests/test_crossSectionTable.py
@@ -23,8 +23,8 @@
 )
 from armi.physics.neutronics.latticePhysics import ORDER
 from armi.reactor.tests.test_blocks import loadTestBlock
-from armi.reactor.tests.test_reactors import loadTestReactor
 from armi.settings import Settings
+from armi.testing import loadTestReactor
 from armi.tests import ISOAA_PATH
 
 
diff --git a/armi/physics/neutronics/tests/test_macroXSGenerationInterface.py b/armi/physics/neutronics/tests/test_macroXSGenerationInterface.py
index 6131c17a8..2b202fdcd 100644
--- a/armi/physics/neutronics/tests/test_macroXSGenerationInterface.py
+++ b/armi/physics/neutronics/tests/test_macroXSGenerationInterface.py
@@ -20,8 +20,8 @@
 from armi.physics.neutronics.macroXSGenerationInterface import (
     MacroXSGenerationInterface,
 )
-from armi.reactor.tests.test_reactors import loadTestReactor
 from armi.settings import Settings
+from armi.testing import loadTestReactor
 from armi.tests import ISOAA_PATH
 
 
diff --git a/armi/reactor/converters/parameterSweeps/tests/test_paramSweepConverters.py b/armi/reactor/converters/parameterSweeps/tests/test_paramSweepConverters.py
index 81f87fa96..af7d0dd6f 100644
--- a/armi/reactor/converters/parameterSweeps/tests/test_paramSweepConverters.py
+++ b/armi/reactor/converters/parameterSweeps/tests/test_paramSweepConverters.py
@@ -22,7 +22,7 @@
     ParameterSweepConverter,
     SettingsModifier,
 )
-from armi.reactor.tests.test_reactors import loadTestReactor
+from armi.testing import loadTestReactor
 from armi.tests import TEST_ROOT
 
 THIS_DIR = os.path.dirname(__file__)
diff --git a/armi/reactor/converters/tests/test_axialExpansionChanger.py b/armi/reactor/converters/tests/test_axialExpansionChanger.py
index a8a4708b9..49bb32bb4 100644
--- a/armi/reactor/converters/tests/test_axialExpansionChanger.py
+++ b/armi/reactor/converters/tests/test_axialExpansionChanger.py
@@ -40,7 +40,7 @@
     areAxiallyLinked,
 )
 from armi.reactor.flags import Flags
-from armi.reactor.tests.test_reactors import loadTestReactor, reduceTestReactorRings
+from armi.testing import loadTestReactor, reduceTestReactorRings
 from armi.tests import TEST_ROOT
 from armi.utils import units
 
diff --git a/armi/reactor/converters/tests/test_blockConverter.py b/armi/reactor/converters/tests/test_blockConverter.py
index e32056345..702b8eb38 100644
--- a/armi/reactor/converters/tests/test_blockConverter.py
+++ b/armi/reactor/converters/tests/test_blockConverter.py
@@ -26,7 +26,7 @@
 from armi.reactor.converters import blockConverters
 from armi.reactor.flags import Flags
 from armi.reactor.tests.test_blocks import loadTestBlock
-from armi.reactor.tests.test_reactors import TEST_ROOT, loadTestReactor
+from armi.testing import TEST_ROOT, loadTestReactor
 from armi.utils import hexagon
 from armi.utils.directoryChangers import TemporaryDirectoryChanger
 
diff --git a/armi/reactor/converters/tests/test_geometryConverters.py b/armi/reactor/converters/tests/test_geometryConverters.py
index 0461e5979..5746a18bb 100644
--- a/armi/reactor/converters/tests/test_geometryConverters.py
+++ b/armi/reactor/converters/tests/test_geometryConverters.py
@@ -23,7 +23,7 @@
 from armi.reactor import blocks, geometry, grids
 from armi.reactor.converters import geometryConverters, uniformMesh
 from armi.reactor.flags import Flags
-from armi.reactor.tests.test_reactors import loadTestReactor, reduceTestReactorRings
+from armi.testing import loadTestReactor, reduceTestReactorRings
 from armi.tests import TEST_ROOT, mockRunLogs
 from armi.utils import directoryChangers
 
diff --git a/armi/reactor/converters/tests/test_meshConverters.py b/armi/reactor/converters/tests/test_meshConverters.py
index 348e5d270..14f102139 100644
--- a/armi/reactor/converters/tests/test_meshConverters.py
+++ b/armi/reactor/converters/tests/test_meshConverters.py
@@ -17,7 +17,7 @@
 import unittest
 
 from armi.reactor.converters import geometryConverters, meshConverters
-from armi.reactor.tests.test_reactors import loadTestReactor
+from armi.testing import loadTestReactor
 from armi.tests import TEST_ROOT
 
 
diff --git a/armi/reactor/converters/tests/test_uniformMesh.py b/armi/reactor/converters/tests/test_uniformMesh.py
index 063883e6a..d5d386f56 100644
--- a/armi/reactor/converters/tests/test_uniformMesh.py
+++ b/armi/reactor/converters/tests/test_uniformMesh.py
@@ -23,8 +23,8 @@
 from armi.reactor.converters import uniformMesh
 from armi.reactor.flags import Flags
 from armi.reactor.tests import test_assemblies, test_blocks
-from armi.reactor.tests.test_reactors import loadTestReactor, reduceTestReactorRings
 from armi.settings.fwSettings.globalSettings import CONF_UNIFORM_MESH_MINIMUM_SIZE
+from armi.testing import loadTestReactor, reduceTestReactorRings
 from armi.tests import ISOAA_PATH, TEST_ROOT
 
 
diff --git a/armi/reactor/tests/test_blocks.py b/armi/reactor/tests/test_blocks.py
index 80ff304ec..aa6c914d4 100644
--- a/armi/reactor/tests/test_blocks.py
+++ b/armi/reactor/tests/test_blocks.py
@@ -37,8 +37,8 @@
 from armi.reactor.components import basicShapes, complexShapes
 from armi.reactor.flags import Flags
 from armi.reactor.tests.test_assemblies import makeTestAssembly
-from armi.reactor.tests.test_reactors import TEST_ROOT, loadTestReactor
-from armi.tests import ISOAA_PATH
+from armi.testing import loadTestReactor
+from armi.tests import ISOAA_PATH, TEST_ROOT
 from armi.utils import densityTools, hexagon, units
 from armi.utils.directoryChangers import TemporaryDirectoryChanger
 from armi.utils.units import (
diff --git a/armi/reactor/tests/test_components.py b/armi/reactor/tests/test_components.py
index eed58904c..ad32245e4 100644
--- a/armi/reactor/tests/test_components.py
+++ b/armi/reactor/tests/test_components.py
@@ -48,7 +48,7 @@
     UnshapedVolumetricComponent,
     materials,
 )
-from armi.reactor.tests.test_reactors import loadTestReactor
+from armi.testing import loadTestReactor
 
 
 class TestComponentFactory(unittest.TestCase):
diff --git a/armi/reactor/tests/test_composites.py b/armi/reactor/tests/test_composites.py
index b9cfd9093..861faa80c 100644
--- a/armi/reactor/tests/test_composites.py
+++ b/armi/reactor/tests/test_composites.py
@@ -28,7 +28,7 @@
 from armi.reactor.composites import getReactionRateDict
 from armi.reactor.flags import Flags, TypeSpec
 from armi.reactor.tests.test_blocks import loadTestBlock
-from armi.reactor.tests.test_reactors import loadTestReactor
+from armi.testing import loadTestReactor
 from armi.tests import ISOAA_PATH, mockRunLogs
 
 
diff --git a/armi/reactor/tests/test_parameters.py b/armi/reactor/tests/test_parameters.py
index 38631b904..9f1a5e018 100644
--- a/armi/reactor/tests/test_parameters.py
+++ b/armi/reactor/tests/test_parameters.py
@@ -20,7 +20,7 @@
 
 from armi.reactor import parameters
 from armi.reactor.reactorParameters import makeParametersReadOnly
-from armi.reactor.tests.test_reactors import loadTestReactor
+from armi.testing import loadTestReactor
 from armi.tests import TEST_ROOT
 from armi.utils.directoryChangers import TemporaryDirectoryChanger
 
diff --git a/armi/reactor/tests/test_reactors.py b/armi/reactor/tests/test_reactors.py
index 70ddf96ca..561c55247 100644
--- a/armi/reactor/tests/test_reactors.py
+++ b/armi/reactor/tests/test_reactors.py
@@ -36,11 +36,11 @@
     CONF_ASSEM_FLAGS_SKIP_AXIAL_EXP,
     CONF_SORT_REACTOR,
 )
-from armi.tests import ARMI_RUN_PATH, TEST_ROOT, mockRunLogs
+from armi.testing import loadTestReactor, reduceTestReactorRings  # noqa: F401
+from armi.tests import TEST_ROOT, mockRunLogs
 from armi.utils import directoryChangers
 
-THIS_DIR = os.path.dirname(__file__)
-TEST_REACTOR = None  # pickled string of test reactor (for fast caching)
+_THIS_DIR = os.path.dirname(__file__)
 
 
 def buildOperatorOfEmptyHexBlocks(customSettings=None):
@@ -125,95 +125,6 @@ def buildOperatorOfEmptyCartesianBlocks(customSettings=None):
     return o
 
 
-"""
-NOTE: If this reactor had 3 rings instead of 9, most unit tests that use it
-go 4 times faster (based on testing). The problem is it would breat a LOT
-of downstream tests that import this method. Probably still worth it though.
-"""
-
-
-def loadTestReactor(
-    inputFilePath=TEST_ROOT,
-    customSettings=None,
-    inputFileName="armiRun.yaml",
-):
-    """
-    Loads a test reactor. Can be used in other test modules.
-
-    Parameters
-    ----------
-    inputFilePath : str, default=TEST_ROOT
-        Path to the directory of the input file.
-
-    customSettings : dict with str keys and values of any type, default=None
-        For each key in customSettings, the cs which is loaded from the
-        armiRun.yaml will be overwritten to the value given in customSettings
-        for that key.
-
-    inputFileName : str, default="armiRun.yaml"
-        Name of the input file to run.
-
-    Returns
-    -------
-    o : Operator
-    r : Reactor
-    """
-    global TEST_REACTOR
-    fName = os.path.join(inputFilePath, inputFileName)
-    customSettings = customSettings or {}
-    isPickeledReactor = fName == ARMI_RUN_PATH and customSettings == {}
-
-    if isPickeledReactor and TEST_REACTOR:
-        # return test reactor only if no custom settings are needed.
-        o, r, assemNum = pickle.loads(TEST_REACTOR)
-        o.reattach(r, o.cs)
-        return o, r
-
-    cs = settings.Settings(fName=fName)
-
-    # Overwrite settings if desired
-    if customSettings:
-        cs = cs.modified(newSettings=customSettings)
-
-    if "verbosity" not in customSettings:
-        runLog.setVerbosity("error")
-
-    newSettings = {}
-    cs = cs.modified(newSettings=newSettings)
-
-    o = operators.factory(cs)
-    r = reactors.loadFromCs(cs)
-
-    o.initializeInterfaces(r)
-
-    o.r.core.regenAssemblyLists()
-
-    if isPickeledReactor:
-        # cache it for fast load for other future tests
-        # protocol=2 allows for classes with __slots__ but not __getstate__ to be pickled
-        TEST_REACTOR = pickle.dumps((o, o.r, o.r.p.maxAssemNum), protocol=2)
-
-    return o, o.r
-
-
-def reduceTestReactorRings(r, cs, maxNumRings):
-    """Helper method for the test reactor above.
-
-    The goal is to reduce the size of the reactor for tests that don't neeed
-    such a large reactor, and would run much faster with a smaller one.
-    """
-    maxRings = r.core.getNumRings()
-    if maxNumRings > maxRings:
-        runLog.info("The test reactor has a maximum of {} rings.".format(maxRings))
-        return
-    elif maxNumRings <= 1:
-        raise ValueError("The test reactor must have multiple rings.")
-
-    # reducing the size of the test reactor, by removing the outer rings
-    for ring in range(maxRings, maxNumRings, -1):
-        r.core.removeAssembliesInRing(ring, cs)
-
-
 class ReactorTests(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
@@ -862,7 +773,8 @@ class MockLib:
         for b in self.r.core.getBlocks():
             b.p.mgFlux = range(5)
             b.p.adjMgFlux = range(5)
-        with directoryChangers.TemporaryDirectoryChanger(root=THIS_DIR):
+
+        with directoryChangers.TemporaryDirectoryChanger(root=_THIS_DIR):
             self.r.core.saveAllFlux()
 
     def test_getFluxVector(self):
diff --git a/armi/testing/__init__.py b/armi/testing/__init__.py
new file mode 100644
index 000000000..994db60d9
--- /dev/null
+++ b/armi/testing/__init__.py
@@ -0,0 +1,117 @@
+# Copyright 2024 TerraPower, LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+Importable testing utilities.
+
+This is a very limited set of ARMI testing tools, meant to be importable as part of the ARMI API.
+The goal is to provide a small set of high quality tools to help downstream ARMI developers write
+tests.
+
+Notes
+-----
+This will not be a catch-all for random unit test functions. Be very sparing here.
+"""
+import os
+import pickle
+
+from armi import operators, runLog, settings
+from armi.reactor import reactors
+from armi.tests import ARMI_RUN_PATH, TEST_ROOT
+
+_THIS_DIR = os.path.dirname(__file__)
+_TEST_REACTOR = None  # pickled string of test reactor (for fast caching)
+
+
+def loadTestReactor(
+    inputFilePath=TEST_ROOT,
+    customSettings=None,
+    inputFileName="armiRun.yaml",
+):
+    """
+    Loads a test reactor. Can be used in other test modules.
+
+    Parameters
+    ----------
+    inputFilePath : str, default=TEST_ROOT
+        Path to the directory of the input file.
+
+    customSettings : dict with str keys and values of any type, default=None
+        For each key in customSettings, the cs which is loaded from the armiRun.yaml will be
+        overwritten to the value given in customSettings for that key.
+
+    inputFileName : str, default="armiRun.yaml"
+        Name of the input file to run.
+
+    Notes
+    -----
+    If the armiRun.yaml test reactor 3 rings instead of 9, most unit tests that use it go 4 times
+    faster (based on testing). The problem is it would breat a LOT of downstream tests that import
+    this method. It is still worth it though.
+
+    Returns
+    -------
+    o : Operator
+    r : Reactor
+    """
+    global _TEST_REACTOR
+    fName = os.path.join(inputFilePath, inputFileName)
+    customSettings = customSettings or {}
+    isPickeledReactor = fName == ARMI_RUN_PATH and customSettings == {}
+
+    if isPickeledReactor and _TEST_REACTOR:
+        # return test reactor only if no custom settings are needed.
+        o, r, assemNum = pickle.loads(_TEST_REACTOR)
+        o.reattach(r, o.cs)
+        return o, r
+
+    cs = settings.Settings(fName=fName)
+
+    # Overwrite settings if desired
+    if customSettings:
+        cs = cs.modified(newSettings=customSettings)
+
+    if "verbosity" not in customSettings:
+        runLog.setVerbosity("error")
+
+    cs = cs.modified(newSettings={})
+    o = operators.factory(cs)
+    r = reactors.loadFromCs(cs)
+
+    o.initializeInterfaces(r)
+    o.r.core.regenAssemblyLists()
+
+    if isPickeledReactor:
+        # cache it for fast load for other future tests protocol=2 allows for classes with __slots__
+        # but not __getstate__ to be pickled
+        _TEST_REACTOR = pickle.dumps((o, o.r, o.r.p.maxAssemNum), protocol=2)
+
+    return o, o.r
+
+
+def reduceTestReactorRings(r, cs, maxNumRings):
+    """Helper method for the test reactor above.
+
+    The goal is to reduce the size of the reactor for tests that don't neeed such a large reactor,
+    and would run much faster with a smaller one.
+    """
+    maxRings = r.core.getNumRings()
+    if maxNumRings > maxRings:
+        runLog.info("The test reactor has a maximum of {} rings.".format(maxRings))
+        return
+    elif maxNumRings <= 1:
+        raise ValueError("The test reactor must have multiple rings.")
+
+    # reducing the size of the test reactor, by removing the outer rings
+    for ring in range(maxRings, maxNumRings, -1):
+        r.core.removeAssembliesInRing(ring, cs)
diff --git a/armi/tests/test_plugins.py b/armi/tests/test_plugins.py
index a8f6a6b68..7852ce653 100644
--- a/armi/tests/test_plugins.py
+++ b/armi/tests/test_plugins.py
@@ -33,7 +33,8 @@
 from armi.reactor.blocks import Block
 from armi.reactor.converters.axialExpansionChanger import AxialExpansionChanger
 from armi.reactor.flags import Flags
-from armi.reactor.tests.test_reactors import TEST_ROOT, loadTestReactor
+from armi.testing import loadTestReactor
+from armi.tests import TEST_ROOT
 
 
 class PluginFlags1(plugins.ArmiPlugin):
diff --git a/armi/utils/tests/test_utils.py b/armi/utils/tests/test_utils.py
index c7982dfd5..b514b5692 100644
--- a/armi/utils/tests/test_utils.py
+++ b/armi/utils/tests/test_utils.py
@@ -20,8 +20,8 @@
 import numpy as np
 
 from armi import utils
-from armi.reactor.tests.test_reactors import loadTestReactor
 from armi.settings.caseSettings import Settings
+from armi.testing import loadTestReactor
 from armi.tests import mockRunLogs
 from armi.utils import (
     codeTiming,
diff --git a/doc/release/0.5.rst b/doc/release/0.5.rst
index f730979d6..0e49b8e5a 100644
--- a/doc/release/0.5.rst
+++ b/doc/release/0.5.rst
@@ -4,11 +4,13 @@ ARMI v0.5 Release Notes
 
 ARMI v0.5.1
 ===========
-Release Date: TBD
+Release Date: TBD (March-ish, 2025)
 
 New Features
 ------------
 #. Move instead of copy files from TemporaryDirectoryChanger. (`PR#2022 <https://github.com/terrapower/armi/pull/2022>`_)
+#. Creating the ``armi.testing`` module, to share ARMI testing tools. (`PR#2028 <https://github.com/terrapower/armi/pull/2028>`_)
+#. TBD
 
 API Changes
 -----------