diff --git a/interfaces/cython/cantera/__init__.py b/interfaces/cython/cantera/__init__.py
index 023fa3883fd..e0fe4e9c40e 100644
--- a/interfaces/cython/cantera/__init__.py
+++ b/interfaces/cython/cantera/__init__.py
@@ -11,10 +11,11 @@
 
 import os
 import sys
+from pathlib import Path
 import warnings
 
 warnings.filterwarnings('default', module='cantera')
-add_directory(os.path.join(os.path.dirname(__file__), 'data'))
+add_directory(Path(__file__).parent / "data")
 add_directory('.')  # Move current working directory to the front of the path
 
 # Python interpreter used for converting mechanisms
diff --git a/interfaces/cython/cantera/base.pyx b/interfaces/cython/cantera/base.pyx
index f3a60801d63..652585ee623 100644
--- a/interfaces/cython/cantera/base.pyx
+++ b/interfaces/cython/cantera/base.pyx
@@ -2,6 +2,7 @@
 # at https://cantera.org/license.txt for license and copyright information.
 
 from collections import defaultdict as _defaultdict
+from pathlib import PurePath
 
 cdef class _SolutionBase:
     def __cinit__(self, infile='', name='', adjacent=(), origin=None,
@@ -53,6 +54,8 @@ cdef class _SolutionBase:
         self.transport = NULL
 
         # Parse inputs
+        if isinstance(infile, PurePath):
+            infile = str(infile)
         if infile.endswith('.yml') or infile.endswith('.yaml') or yaml:
             self._init_yaml(infile, name, adjacent, yaml)
         elif infile or source:
diff --git a/interfaces/cython/cantera/ck2yaml.py b/interfaces/cython/cantera/ck2yaml.py
index 8173c0ac884..eef92ed9153 100644
--- a/interfaces/cython/cantera/ck2yaml.py
+++ b/interfaces/cython/cantera/ck2yaml.py
@@ -1375,8 +1375,9 @@ def load_extra_file(self, path):
         """
         Load YAML-formatted entries from ``path`` on disk.
         """
+        yaml_ = yaml.YAML()
         with open(path, 'rt', encoding="utf-8") as stream:
-            yml = yaml.round_trip_load(stream)
+            yml = yaml_.load(stream)
 
         # do not overwrite reserved field names
         reserved = {'generator', 'input-files', 'cantera-version', 'date',
diff --git a/interfaces/cython/cantera/onedim.pyx b/interfaces/cython/cantera/onedim.pyx
index b2437b763fe..87964b28887 100644
--- a/interfaces/cython/cantera/onedim.pyx
+++ b/interfaces/cython/cantera/onedim.pyx
@@ -1411,7 +1411,7 @@ cdef class Sim1D:
         ...        description='solution with energy eqn. disabled')
 
         """
-        self.sim.save(stringify(filename), stringify(name),
+        self.sim.save(stringify(str(filename)), stringify(name),
                       stringify(description), loglevel)
 
     def restore(self, filename='soln.xml', name='solution', loglevel=2):
@@ -1427,7 +1427,7 @@ cdef class Sim1D:
 
         >>> s.restore(filename='save.xml', name='energy_off')
         """
-        self.sim.restore(stringify(filename), stringify(name), loglevel)
+        self.sim.restore(stringify(str(filename)), stringify(name), loglevel)
         self._initialized = True
 
     def restore_time_stepping_solution(self):
diff --git a/interfaces/cython/cantera/test/__init__.py b/interfaces/cython/cantera/test/__init__.py
index 14f938347a5..4476c62b0f1 100644
--- a/interfaces/cython/cantera/test/__init__.py
+++ b/interfaces/cython/cantera/test/__init__.py
@@ -1,4 +1,4 @@
-import os
+from pathlib import Path
 import cantera
 
 from .test_composite import *
@@ -15,5 +15,5 @@
 from .test_transport import *
 from .test_utils import *
 
-cantera.add_directory(os.path.join(os.path.dirname(__file__), 'data'))
-cantera.add_directory(os.path.join(os.path.dirname(__file__), '..', 'examples', 'surface_chemistry'))
+cantera.add_directory(Path(__file__) / "data")
+cantera.add_directory(Path(__file__).parents[1] / "examples" / "surface_chemistry")
diff --git a/interfaces/cython/cantera/test/test_composite.py b/interfaces/cython/cantera/test/test_composite.py
index 51fdb1c5cb1..0ae19a2dbf8 100644
--- a/interfaces/cython/cantera/test/test_composite.py
+++ b/interfaces/cython/cantera/test/test_composite.py
@@ -1,16 +1,7 @@
-from os.path import join as pjoin
-import os
 import sys
 
 import numpy as np
 from collections import OrderedDict
-import warnings
-
-try:
-    import ruamel_yaml as yaml
-except ImportError:
-    from ruamel import yaml
-
 
 import cantera as ct
 from cantera.composite import _h5py, _pandas
@@ -22,9 +13,8 @@ class TestModels(utilities.CanteraTest):
     @classmethod
     def setUpClass(cls):
         utilities.CanteraTest.setUpClass()
-        cls.yml_file = pjoin(cls.test_data_dir, "thermo-models.yaml")
-        with open(cls.yml_file, 'rt', encoding="utf-8") as stream:
-            cls.yml = yaml.safe_load(stream)
+        cls.yml_file = cls.test_data_path / "thermo-models.yaml"
+        cls.yml = utilities.load_yaml(cls.yml_file)
 
     def test_load_thermo_models(self):
         for ph in self.yml['phases']:
@@ -150,7 +140,7 @@ def test_write_csv(self):
         states.TPX = np.linspace(300, 1000, 7), 2e5, 'H2:0.5, O2:0.4'
         states.equilibrate('HP')
 
-        outfile = pjoin(self.test_work_dir, 'solutionarray.csv')
+        outfile = self.test_work_path / "solutionarray.csv"
         states.write_csv(outfile)
 
         data = np.genfromtxt(outfile, names=True, delimiter=',')
@@ -167,7 +157,7 @@ def test_write_csv(self):
     def test_write_csv_str_column(self):
         states = ct.SolutionArray(self.gas, 3, extra={'spam': 'eggs'})
 
-        outfile = pjoin(self.test_work_dir, 'solutionarray.csv')
+        outfile = self.test_work_path / "solutionarray.csv"
         states.write_csv(outfile)
 
         b = ct.SolutionArray(self.gas, extra={'spam'})
@@ -177,7 +167,7 @@ def test_write_csv_str_column(self):
     def test_write_csv_multidim_column(self):
         states = ct.SolutionArray(self.gas, 3, extra={'spam': np.zeros((3, 5,))})
 
-        outfile = pjoin(self.test_work_dir, 'solutionarray.csv')
+        outfile = self.test_work_path / "solutionarray.csv"
         with self.assertRaisesRegex(NotImplementedError, 'not supported'):
             states.write_csv(outfile)
 
@@ -194,9 +184,10 @@ def test_to_pandas(self):
 
     @utilities.unittest.skipIf(isinstance(_h5py, ImportError), "h5py is not installed")
     def test_write_hdf(self):
-        outfile = pjoin(self.test_work_dir, 'solutionarray.h5')
-        if os.path.exists(outfile):
-            os.remove(outfile)
+        outfile = self.test_work_path / "solutionarray.h5"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if outfile.is_file():
+            outfile.unlink()
 
         extra = {'foo': range(7), 'bar': range(7)}
         meta = {'spam': 'eggs', 'hello': 'world'}
@@ -239,9 +230,10 @@ def test_write_hdf(self):
 
     @utilities.unittest.skipIf(isinstance(_h5py, ImportError), "h5py is not installed")
     def test_write_hdf_str_column(self):
-        outfile = pjoin(self.test_work_dir, 'solutionarray.h5')
-        if os.path.exists(outfile):
-            os.remove(outfile)
+        outfile = self.test_work_path / "solutionarray.h5"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if outfile.is_file():
+            outfile.unlink()
 
         states = ct.SolutionArray(self.gas, 3, extra={'spam': 'eggs'})
         states.write_hdf(outfile, mode='w')
@@ -252,9 +244,10 @@ def test_write_hdf_str_column(self):
 
     @utilities.unittest.skipIf(isinstance(_h5py, ImportError), "h5py is not installed")
     def test_write_hdf_multidim_column(self):
-        outfile = pjoin(self.test_work_dir, 'solutionarray.h5')
-        if os.path.exists(outfile):
-            os.remove(outfile)
+        outfile = self.test_work_path / "solutionarray.h5"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if outfile.is_file():
+            outfile.unlink()
 
         states = ct.SolutionArray(self.gas, 3, extra={'spam': [[1, 2], [3, 4], [5, 6]]})
         states.write_hdf(outfile, mode='w')
@@ -478,8 +471,7 @@ def test_yaml_simple(self):
         gas.equilibrate('HP')
         gas.TP = 1500, ct.one_atm
         gas.write_yaml('h2o2-generated.yaml')
-        with open('h2o2-generated.yaml', 'r') as infile:
-            generated = yaml.safe_load(infile)
+        generated = utilities.load_yaml("h2o2-generated.yaml")
         for key in ('generator', 'date', 'phases', 'species', 'reactions'):
             self.assertIn(key, generated)
         self.assertEqual(generated['phases'][0]['transport'], 'mixture-averaged')
@@ -503,10 +495,8 @@ def test_yaml_outunits(self):
         gas.TP = 1500, ct.one_atm
         units = {'length': 'cm', 'quantity': 'mol', 'energy': 'cal'}
         gas.write_yaml('h2o2-generated.yaml', units=units)
-        with open('h2o2-generated.yaml') as infile:
-            generated = yaml.safe_load(infile)
-        with open(pjoin(self.cantera_data, "h2o2.yaml")) as infile:
-            original = yaml.safe_load(infile)
+        generated = utilities.load_yaml("h2o2-generated.yaml")
+        original = utilities.load_yaml(self.cantera_data_path / "h2o2.yaml")
         self.assertEqual(generated['units'], units)
 
         for r1, r2 in zip(original['reactions'], generated['reactions']):
@@ -529,8 +519,7 @@ def test_yaml_surface(self):
         surf.coverages = np.ones(surf.n_species)
         surf.write_yaml('ptcombust-generated.yaml')
 
-        with open('ptcombust-generated.yaml') as infile:
-            generated = yaml.safe_load(infile)
+        generated = utilities.load_yaml("ptcombust-generated.yaml")
         for key in ('phases', 'species', 'gas-reactions', 'Pt_surf-reactions'):
             self.assertIn(key, generated)
         self.assertEqual(len(generated['gas-reactions']), gas.n_reactions)
diff --git a/interfaces/cython/cantera/test/test_convert.py b/interfaces/cython/cantera/test/test_convert.py
index 24ba4900a60..7ae4c871019 100644
--- a/interfaces/cython/cantera/test/test_convert.py
+++ b/interfaces/cython/cantera/test/test_convert.py
@@ -1,40 +1,33 @@
-import os
-from os.path import join as pjoin
 import itertools
 from pathlib import Path
 import logging
 import io
-import sys
 
 from . import utilities
 import cantera as ct
 from cantera import ck2cti, ck2yaml, cti2yaml, ctml2yaml
 
-try:
-    import ruamel_yaml as yaml
-except ImportError:
-    from ruamel import yaml
-
 
 class converterTestCommon:
     def convert(self, inputFile, thermo=None, transport=None,
                 surface=None, output=None, extra=None,
                 quiet=True, permissive=None):
         if output is None:
-            output = inputFile[:-4]  # strip '.inp'
+            output = Path(inputFile).stem  # strip '.inp'
         if inputFile is not None:
-            inputFile = pjoin(self.test_data_dir, inputFile)
+            inputFile = self.test_data_path / inputFile
         if thermo is not None:
-            thermo = pjoin(self.test_data_dir, thermo)
+            thermo = self.test_data_path / thermo
         if transport is not None:
-            transport = pjoin(self.test_data_dir, transport)
+            transport = self.test_data_path / transport
         if surface is not None:
-            surface = pjoin(self.test_data_dir, surface)
+            surface = self.test_data_path / surface
         if extra is not None:
-            extra = pjoin(self.test_data_dir, extra)
-        output = pjoin(self.test_work_dir, output + self.ext)
-        if os.path.exists(output):
-            os.remove(output)
+            extra = self.test_data_path / extra
+        output = self.test_work_path / (output + self.ext)
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if output.is_file():
+            output.unlink()
         self._convert(inputFile, thermo=thermo, transport=transport,
             surface=surface, output=output, extra=extra,
             quiet=quiet, permissive=permissive)
@@ -367,14 +360,14 @@ def test_empty_reaction_section(self):
 
     def test_reaction_comments1(self):
         output = self.convert('pdep-test.inp')
-        text = Path(output).read_text()
+        text = output.read_text()
         self.assertIn('Generic mechanism header', text)
         self.assertIn('Single PLOG reaction', text)
         self.assertIn('Multiple PLOG expressions at the same pressure', text)
 
     def test_reaction_comments2(self):
         output = self.convert('explicit-third-bodies.inp', thermo='dummy-thermo.dat')
-        text = Path(output).read_text()
+        text = output.read_text()
         self.assertIn('An end of line comment', text)
         self.assertIn('A comment after the last reaction', text)
 
@@ -478,26 +471,24 @@ def test_extra(self):
                      transport='gri30_tran.dat', output='gri30_extra',
                      extra='extra.yaml')
 
-        output = pjoin(self.test_work_dir, 'gri30_extra' + self.ext)
-        with open(output, 'rt', encoding="utf-8") as stream:
-            yml = yaml.safe_load(stream)
+        output = self.test_work_path / ("gri30_extra" + self.ext)
+        yml = utilities.load_yaml(output)
 
         desc = yml['description'].split('\n')[-1]
         self.assertEqual(desc, 'This is an alternative description.')
         for key in ['foo', 'bar']:
             self.assertIn(key, yml.keys())
-        # This test tests it can convert the SRI parameters when D or E equal to 0
-   
+
     def test_sri_zero(self):
+        # This test tests it can convert the SRI parameters when D or E equal to 0
         self.convert('sri_convert_test.txt')
-        output = pjoin(self.test_work_dir, 'sri_convert_test' + self.ext)
-        with open(output, 'r') as f:
-            mech = yaml.safe_load(f)
+        output = self.test_work_path / ("sri_convert_test" + self.ext)
+        mech = utilities.load_yaml(output)
         D = mech['reactions'][0]['SRI']['D']
         E = mech['reactions'][0]['SRI']['E']
         self.assertEqual(D, 0)
         self.assertEqual(E, 0)
-        
+
     def test_duplicate_reactions(self):
         # Running a test this way instead of using the convertMech function
         # tests the behavior of the ck2yaml.main function and the mechanism
@@ -517,8 +508,8 @@ def test_duplicate_reactions(self):
 
         with self.assertRaises(SystemExit):
             ck2yaml.main([
-                '--input={}/undeclared-duplicate-reactions.inp'.format(self.test_data_dir),
-                '--thermo={}/dummy-thermo.dat'.format(self.test_data_dir)])
+                f"--input={self.test_data_path}/undeclared-duplicate-reactions.inp",
+                f"--thermo={self.test_data_path}/dummy-thermo.dat"])
 
         # Put the original logger back in place
         logger.handlers.clear()
@@ -579,8 +570,7 @@ def test_long_source_input(self):
 
         gas = ct.Solution('pdep-test.yaml')
 
-        with open(pjoin(self.test_data_dir, 'pdep-test.cti'), 'r') as f:
-            data = f.read()
+        data = (self.test_data_path / "pdep-test.cti").read_text()
         data_size_2048kB = data + ' '*2048*1024
         gas2 = ct.Solution(source=data_size_2048kB)
 
@@ -594,8 +584,7 @@ def test_short_source_input(self):
 
         gas = ct.Solution('pdep-test.yaml')
 
-        with open(pjoin(self.test_data_dir, 'pdep-test.cti'), 'r') as f:
-            data = f.read()
+        data = (self.test_data_path / "pdep-test.cti").read_text()
         data_size_32kB = data + ' '*18000
         gas2 = ct.Solution(source=data_size_32kB)
 
@@ -674,8 +663,10 @@ def checkTransport(self, ctiPhase, yamlPhase, temperatures,
 
     @utilities.slow_test
     def test_gri30(self):
-        cti2yaml.convert(Path(self.cantera_data).joinpath('gri30.cti'),
-                         Path(self.test_work_dir).joinpath('gri30.yaml'))
+        cti2yaml.convert(
+            self.cantera_data_path / "gri30.cti",
+            self.test_work_path / "gri30.yaml",
+        )
         ctiPhase, yamlPhase = self.checkConversion('gri30')
         X = {'O2': 0.3, 'H2': 0.1, 'CH4': 0.2, 'CO2': 0.4}
         ctiPhase.X = X
@@ -685,15 +676,19 @@ def test_gri30(self):
         self.checkTransport(ctiPhase, yamlPhase, [298, 1001, 2400])
 
     def test_pdep(self):
-        cti2yaml.convert(Path(self.test_data_dir).joinpath('pdep-test.cti'),
-                         Path(self.test_work_dir).joinpath('pdep-test.yaml'))
+        cti2yaml.convert(
+            self.test_data_path / "pdep-test.cti",
+            self.test_work_path / "pdep-test.yaml",
+        )
         ctiPhase, yamlPhase = self.checkConversion('pdep-test')
         self.checkKinetics(ctiPhase, yamlPhase, [300, 1000, 2200],
                            [100, ct.one_atm, 2e5, 2e6, 9.9e6])
 
     def test_ptcombust(self):
-        cti2yaml.convert(Path(self.cantera_data).joinpath('ptcombust.cti'),
-                         Path(self.test_work_dir).joinpath('ptcombust.yaml'))
+        cti2yaml.convert(
+            self.cantera_data_path / "ptcombust.cti",
+            self.test_work_path / "ptcombust.yaml",
+        )
         ctiGas, yamlGas = self.checkConversion('ptcombust')
         ctiSurf, yamlSurf = self.checkConversion('ptcombust', ct.Interface,
             name='Pt_surf', ctiphases=[ctiGas], yamlphases=[yamlGas])
@@ -704,8 +699,10 @@ def test_ptcombust(self):
 
     @utilities.slow_test
     def test_ptcombust_motzwise(self):
-        cti2yaml.convert(Path(self.test_data_dir).joinpath('ptcombust-motzwise.cti'),
-                         Path(self.test_work_dir).joinpath('ptcombust-motzwise.yaml'))
+        cti2yaml.convert(
+            self.test_data_path / "ptcombust-motzwise.cti",
+            self.test_work_path / "ptcombust-motzwise.yaml",
+        )
         ctiGas, yamlGas = self.checkConversion('ptcombust-motzwise')
         ctiSurf, yamlSurf = self.checkConversion('ptcombust-motzwise', ct.Interface,
             name='Pt_surf', ctiphases=[ctiGas], yamlphases=[yamlGas])
@@ -716,8 +713,10 @@ def test_ptcombust_motzwise(self):
         self.checkKinetics(ctiSurf, yamlSurf, [900], [101325])
 
     def test_sofc(self):
-        cti2yaml.convert(Path(self.cantera_data).joinpath('sofc.cti'),
-                         Path(self.test_work_dir).joinpath('sofc.yaml'))
+        cti2yaml.convert(
+            self.cantera_data_path / "sofc.cti",
+            self.test_work_path / "sofc.yaml",
+        )
         ctiGas, yamlGas = self.checkConversion('sofc')
         ctiMetal, yamlMetal = self.checkConversion('sofc', name='metal')
         ctiOxide, yamlOxide = self.checkConversion('sofc', name='oxide_bulk')
@@ -740,9 +739,11 @@ def test_sofc(self):
 
     @utilities.slow_test
     def test_liquidvapor(self):
-        output_file = Path(self.test_work_dir).joinpath('liquidvapor.yaml')
-        cti2yaml.convert(Path(self.cantera_data).joinpath('liquidvapor.cti'),
-                         output_file)
+        output_file = self.test_work_path / "liquidvapor.yaml"
+        cti2yaml.convert(
+            self.cantera_data_path / "liquidvapor.cti",
+            output_file,
+        )
         for name in ['water', 'nitrogen', 'methane', 'hydrogen', 'oxygen',
                      'hfc134a', 'carbondioxide', 'heptane']:
             ctiPhase, yamlPhase = self.checkConversion('liquidvapor', name=name)
@@ -753,8 +754,10 @@ def test_liquidvapor(self):
         output_file.unlink()
 
     def test_Redlich_Kwong_CO2(self):
-        cti2yaml.convert(Path(self.test_data_dir).joinpath('co2_RK_example.cti'),
-                         Path(self.test_work_dir).joinpath('co2_RK_example.yaml'))
+        cti2yaml.convert(
+            self.test_data_path / "co2_RK_example.cti",
+            self.test_work_path / "co2_RK_example.yaml",
+        )
         ctiGas, yamlGas = self.checkConversion('co2_RK_example')
         for P in [1e5, 2e6, 1.3e7]:
             yamlGas.TP = ctiGas.TP = 300, P
@@ -762,16 +765,20 @@ def test_Redlich_Kwong_CO2(self):
 
     @utilities.slow_test
     def test_Redlich_Kwong_ndodecane(self):
-        cti2yaml.convert(Path(self.cantera_data).joinpath('nDodecane_Reitz.cti'),
-                         Path(self.test_work_dir).joinpath('nDodecane_Reitz.yaml'))
+        cti2yaml.convert(
+            self.cantera_data_path / "nDodecane_Reitz.cti",
+            self.test_work_path / "nDodecane_Reitz.yaml",
+        )
         ctiGas, yamlGas = self.checkConversion('nDodecane_Reitz')
         self.checkThermo(ctiGas, yamlGas, [300, 400, 500])
         self.checkKinetics(ctiGas, yamlGas, [300, 500, 1300], [1e5, 2e6, 1.4e7],
                            1e-6)
 
     def test_diamond(self):
-        cti2yaml.convert(Path(self.cantera_data).joinpath('diamond.cti'),
-                         Path(self.test_work_dir).joinpath('diamond.yaml'))
+        cti2yaml.convert(
+            self.cantera_data_path / "diamond.cti",
+            self.test_work_path / "diamond.yaml",
+        )
         ctiGas, yamlGas = self.checkConversion('diamond', name='gas')
         ctiSolid, yamlSolid = self.checkConversion('diamond', name='diamond')
         ctiSurf, yamlSurf = self.checkConversion('diamond',
@@ -782,8 +789,10 @@ def test_diamond(self):
         self.checkKinetics(ctiSurf, yamlSurf, [400, 800], [2e5])
 
     def test_lithium_ion_battery(self):
-        cti2yaml.convert(Path(self.cantera_data).joinpath('lithium_ion_battery.cti'),
-                         Path(self.test_work_dir).joinpath('lithium_ion_battery.yaml'))
+        cti2yaml.convert(
+            self.cantera_data_path / "lithium_ion_battery.cti",
+            self.test_work_path / "lithium_ion_battery.yaml",
+        )
         name = 'lithium_ion_battery'
         ctiAnode, yamlAnode = self.checkConversion(name, name='anode')
         ctiCathode, yamlCathode = self.checkConversion(name, name='cathode')
@@ -819,8 +828,10 @@ def test_lithium_ion_battery(self):
         self.checkKinetics(ctiCathodeInt, yamlCathodeInt, [300], [1e5])
 
     def test_ch4_ion(self):
-        cti2yaml.convert(Path(self.test_data_dir).joinpath("ch4_ion.cti"),
-                          Path(self.test_work_dir).joinpath("ch4_ion.yaml"))
+        cti2yaml.convert(
+            self.test_data_path / "ch4_ion.cti",
+            self.test_work_path / "ch4_ion.yaml",
+        )
         ctiGas, yamlGas = self.checkConversion("ch4_ion")
         self.checkThermo(ctiGas, yamlGas, [300, 500, 1300, 2000])
         self.checkKinetics(ctiGas, yamlGas, [900, 1800], [2e5, 20e5])
@@ -900,8 +911,8 @@ def checkTransport(self, ctmlPhase, yamlPhase, temperatures,
     @utilities.slow_test
     def test_gri30(self):
         ctml2yaml.convert(
-            Path(self.cantera_data).joinpath('gri30.xml'),
-            Path(self.test_work_dir).joinpath('gri30.yaml'),
+            self.cantera_data_path / "gri30.xml",
+            self.test_work_path / "gri30.yaml",
         )
         ctmlPhase, yamlPhase = self.checkConversion('gri30')
         X = {'O2': 0.3, 'H2': 0.1, 'CH4': 0.2, 'CO2': 0.4}
@@ -913,8 +924,8 @@ def test_gri30(self):
 
     def test_pdep(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath('pdep-test.xml'),
-            Path(self.test_work_dir).joinpath('pdep-test.yaml'),
+            self.test_data_path / "pdep-test.xml",
+            self.test_work_path / "pdep-test.yaml",
         )
         ctmlPhase, yamlPhase = self.checkConversion('pdep-test')
         self.checkKinetics(ctmlPhase, yamlPhase, [300, 1000, 2200],
@@ -922,8 +933,8 @@ def test_pdep(self):
 
     def test_ptcombust(self):
         ctml2yaml.convert(
-            Path(self.cantera_data).joinpath('ptcombust.xml'),
-            Path(self.test_work_dir).joinpath('ptcombust.yaml'),
+            self.cantera_data_path / "ptcombust.xml",
+            self.test_work_path / "ptcombust.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion('ptcombust')
         ctmlSurf, yamlSurf = self.checkConversion('ptcombust', ct.Interface,
@@ -935,8 +946,8 @@ def test_ptcombust(self):
 
     def test_ptcombust_motzwise(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath('ptcombust-motzwise.xml'),
-            Path(self.test_work_dir).joinpath('ptcombust-motzwise.yaml'),
+            self.test_data_path / "ptcombust-motzwise.xml",
+            self.test_work_path / "ptcombust-motzwise.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion('ptcombust-motzwise')
         ctmlSurf, yamlSurf = self.checkConversion('ptcombust-motzwise', ct.Interface,
@@ -948,8 +959,8 @@ def test_ptcombust_motzwise(self):
 
     def test_sofc(self):
         ctml2yaml.convert(
-            Path(self.cantera_data).joinpath('sofc.xml'),
-            Path(self.test_work_dir).joinpath('sofc.yaml'),
+            self.cantera_data_path / "sofc.xml",
+            self.test_work_path / "sofc.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion('sofc')
         ctmlMetal, yamlMetal = self.checkConversion('sofc', name='metal')
@@ -972,9 +983,9 @@ def test_sofc(self):
         self.checkKinetics(ctml_tpb, yaml_tpb, [900, 1000, 1100], [1e5])
 
     def test_liquidvapor(self):
-        output_file = Path(self.test_work_dir).joinpath('liquidvapor.yaml')
+        output_file = self.test_work_path / "liquidvapor.yaml"
         ctml2yaml.convert(
-            Path(self.cantera_data).joinpath('liquidvapor.xml'), output_file,
+            self.cantera_data_path / "liquidvapor.xml", output_file,
         )
         for name in ['water', 'nitrogen', 'methane', 'hydrogen', 'oxygen',
                      'hfc134a', 'carbondioxide', 'heptane']:
@@ -987,8 +998,8 @@ def test_liquidvapor(self):
 
     def test_Redlich_Kwong_CO2(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath('co2_RK_example.xml'),
-            Path(self.test_work_dir).joinpath('co2_RK_example.yaml'),
+            self.test_data_path / "co2_RK_example.xml",
+            self.test_work_path / "co2_RK_example.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion('co2_RK_example')
         for P in [1e5, 2e6, 1.3e7]:
@@ -998,8 +1009,8 @@ def test_Redlich_Kwong_CO2(self):
     @utilities.slow_test
     def test_Redlich_Kwong_ndodecane(self):
         ctml2yaml.convert(
-            Path(self.cantera_data).joinpath('nDodecane_Reitz.xml'),
-            Path(self.test_work_dir).joinpath('nDodecane_Reitz.yaml'),
+            self.cantera_data_path / "nDodecane_Reitz.xml",
+            self.test_work_path / "nDodecane_Reitz.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion('nDodecane_Reitz')
         self.checkThermo(ctmlGas, yamlGas, [300, 400, 500])
@@ -1008,8 +1019,8 @@ def test_Redlich_Kwong_ndodecane(self):
 
     def test_diamond(self):
         ctml2yaml.convert(
-            Path(self.cantera_data).joinpath('diamond.xml'),
-            Path(self.test_work_dir).joinpath('diamond.yaml'),
+            self.cantera_data_path / "diamond.xml",
+            self.test_work_path / "diamond.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion('diamond', name='gas')
         ctmlSolid, yamlSolid = self.checkConversion('diamond', name='diamond')
@@ -1023,8 +1034,8 @@ def test_diamond(self):
     def test_lithium_ion_battery(self):
         name = 'lithium_ion_battery'
         ctml2yaml.convert(
-            Path(self.cantera_data).joinpath(name + ".xml"),
-            Path(self.test_work_dir).joinpath(name + ".yaml"),
+            self.cantera_data_path / (name + ".xml"),
+            self.test_work_path / (name + ".yaml"),
         )
         ctmlAnode, yamlAnode = self.checkConversion(name, name='anode')
         ctmlCathode, yamlCathode = self.checkConversion(name, name='cathode')
@@ -1061,8 +1072,8 @@ def test_lithium_ion_battery(self):
 
     def test_noxNeg(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath('noxNeg.xml'),
-            Path(self.test_work_dir).joinpath('noxNeg.yaml'),
+            self.test_data_path / "noxNeg.xml",
+            self.test_work_path / "noxNeg.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion('noxNeg')
         self.checkThermo(ctmlGas, yamlGas, [300, 1000])
@@ -1070,8 +1081,8 @@ def test_noxNeg(self):
 
     def test_ch4_ion(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("ch4_ion.xml"),
-            Path(self.test_work_dir).joinpath("ch4_ion.yaml"),
+            self.test_data_path / "ch4_ion.xml",
+            self.test_work_path / "ch4_ion.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion("ch4_ion")
         self.checkThermo(ctmlGas, yamlGas, [300, 500, 1300, 2000])
@@ -1080,16 +1091,16 @@ def test_ch4_ion(self):
 
     def test_nasa9(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("nasa9-test.xml"),
-            Path(self.test_work_dir).joinpath("nasa9-test.yaml"),
+            self.test_data_path / "nasa9-test.xml",
+            self.test_work_path / "nasa9-test.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion("nasa9-test")
         self.checkThermo(ctmlGas, yamlGas, [300, 500, 1300, 2000])
 
     def test_chemically_activated(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("chemically-activated-reaction.xml"),
-            Path(self.test_work_dir).joinpath("chemically-activated-reaction.yaml"),
+            self.test_data_path / "chemically-activated-reaction.xml",
+            self.test_work_path / "chemically-activated-reaction.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion("chemically-activated-reaction")
         self.checkThermo(ctmlGas, yamlGas, [300, 500, 1300, 2000])
@@ -1097,24 +1108,26 @@ def test_chemically_activated(self):
 
     def test_explicit_forward_order(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("explicit-forward-order.xml"),
-            Path(self.test_work_dir).joinpath("explicit-forward-order.yaml"),
+            self.test_data_path / "explicit-forward-order.xml",
+            self.test_work_path / "explicit-forward-order.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion("explicit-forward-order")
         self.checkThermo(ctmlGas, yamlGas, [300, 500, 1300, 2000])
         self.checkKinetics(ctmlGas, yamlGas, [900, 1800], [2e5, 20e5])
 
     def test_explicit_reverse_rate(self):
-        ctml2yaml.convert(Path(self.test_data_dir).joinpath("explicit-reverse-rate.xml"),
-                          Path(self.test_work_dir).joinpath("explicit-reverse-rate.yaml"))
+        ctml2yaml.convert(
+            self.test_data_path / "explicit-reverse-rate.xml",
+            self.test_work_path / "explicit-reverse-rate.yaml",
+        )
         ctmlGas, yamlGas = self.checkConversion("explicit-reverse-rate")
         self.checkThermo(ctmlGas, yamlGas, [300, 500, 1300, 2000])
         self.checkKinetics(ctmlGas, yamlGas, [900, 1800], [2e5, 20e5])
 
     def test_explicit_third_bodies(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("explicit-third-bodies.xml"),
-            Path(self.test_work_dir).joinpath("explicit-third-bodies.yaml"),
+            self.test_data_path / "explicit-third-bodies.xml",
+            self.test_work_path / "explicit-third-bodies.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion("explicit-third-bodies")
         self.checkThermo(ctmlGas, yamlGas, [300, 500, 1300, 2000])
@@ -1122,8 +1135,8 @@ def test_explicit_third_bodies(self):
 
     def test_fractional_stoich_coeffs(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("frac.xml"),
-            Path(self.test_work_dir).joinpath("frac.yaml"),
+            self.test_data_path / "frac.xml",
+            self.test_work_path / "frac.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion("frac")
         self.checkThermo(ctmlGas, yamlGas, [300, 500, 1300, 2000])
@@ -1131,8 +1144,8 @@ def test_fractional_stoich_coeffs(self):
 
     def test_water_IAPWS95_thermo(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("liquid-water.xml"),
-            Path(self.test_work_dir).joinpath("liquid-water.yaml"),
+            self.test_data_path / "liquid-water.xml",
+            self.test_work_path / "liquid-water.yaml",
         )
         ctmlWater, yamlWater = self.checkConversion("liquid-water")
         self.checkThermo(ctmlWater, yamlWater, [300, 500, 1300, 2000], pressure=22064000.0)
@@ -1147,8 +1160,8 @@ def test_water_IAPWS95_thermo(self):
 
     def test_hmw_nacl_phase(self):
         basename = "HMW_NaCl_sp1977_alt"
-        xml_file = Path(self.test_data_dir).joinpath(basename).with_suffix(".xml")
-        yaml_file = Path(self.test_data_dir).joinpath(basename).with_suffix(".yaml")
+        xml_file = self.test_data_path / (basename + ".xml")
+        yaml_file = self.test_data_path / (basename + ".yaml")
         ctml2yaml.convert(xml_file, yaml_file)
 
         # Can only be loaded by ThermoPhase due to a bug in TransportFactory
@@ -1162,16 +1175,16 @@ def test_hmw_nacl_phase(self):
 
     def test_NaCl_solid_phase(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("NaCl_Solid.xml"),
-            Path(self.test_work_dir).joinpath("NaCl_Solid.yaml"),
+            self.test_data_path / "NaCl_Solid.xml",
+            self.test_work_path / "NaCl_Solid.yaml",
         )
         ctmlPhase, yamlPhase = self.checkConversion("NaCl_Solid")
         self.checkThermo(ctmlPhase, yamlPhase, [300, 500, 1300, 2000])
 
     def test_DH_NaCl_phase(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("debye-huckel-all.xml"),
-            Path(self.test_work_dir).joinpath("debye-huckel-all.yaml"),
+            self.test_data_path / "debye-huckel-all.xml",
+            self.test_work_path / "debye-huckel-all.yaml",
         )
         for name in [
             "debye-huckel-dilute",
@@ -1191,8 +1204,8 @@ def test_DH_NaCl_phase(self):
 
     def test_Maskell_solid_soln(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("MaskellSolidSolnPhase_valid.xml"),
-            Path(self.test_work_dir).joinpath("MaskellSolidSolnPhase_valid.yaml"),
+            self.test_data_path / "MaskellSolidSolnPhase_valid.xml",
+            self.test_work_path / "MaskellSolidSolnPhase_valid.yaml",
         )
 
         ctmlPhase, yamlPhase = self.checkConversion("MaskellSolidSolnPhase_valid")
@@ -1204,8 +1217,8 @@ def test_Maskell_solid_soln(self):
 
     def test_mock_ion(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("mock_ion.xml"),
-            Path(self.test_work_dir).joinpath("mock_ion.yaml"),
+            self.test_data_path / "mock_ion.xml",
+            self.test_work_path / "mock_ion.yaml",
         )
         ctmlPhase = ct.ThermoPhase("mock_ion.xml")
         yamlPhase = ct.ThermoPhase("mock_ion.yaml")
@@ -1225,8 +1238,8 @@ def test_mock_ion(self):
 
     def test_Redlich_Kister(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("RedlichKisterVPSSTP_valid.xml"),
-            Path(self.test_work_dir).joinpath("RedlichKisterVPSSTP_valid.yaml"),
+            self.test_data_path / "RedlichKisterVPSSTP_valid.xml",
+            self.test_work_path / "RedlichKisterVPSSTP_valid.yaml",
         )
 
         ctmlPhase, yamlPhase = self.checkConversion("RedlichKisterVPSSTP_valid")
@@ -1234,16 +1247,16 @@ def test_Redlich_Kister(self):
 
     def test_species_names(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath('species-names.xml'),
-            Path(self.test_work_dir).joinpath('species-names.yaml'),
+            self.test_data_path / "species-names.xml",
+            self.test_work_path / "species-names.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion('species-names')
         self.checkThermo(ctmlGas, yamlGas, [300, 500, 1300, 2000])
 
     def test_sri_falloff_reaction(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("sri-falloff.xml"),
-            Path(self.test_work_dir).joinpath("sri-falloff.yaml"),
+            self.test_data_path / "sri-falloff.xml",
+            self.test_work_path / "sri-falloff.yaml",
         )
         ctmlGas, yamlGas = self.checkConversion("sri-falloff")
         self.checkThermo(ctmlGas, yamlGas, [300, 500, 1300, 2000])
@@ -1251,8 +1264,8 @@ def test_sri_falloff_reaction(self):
 
     def test_vpss_and_hkft(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("pdss_hkft.xml"),
-            Path(self.test_work_dir).joinpath("pdss_hkft.yaml"),
+            self.test_data_path / "pdss_hkft.xml",
+            self.test_work_path / "pdss_hkft.yaml",
         )
         ctmlPhase = ct.ThermoPhase("pdss_hkft.xml")
         yamlPhase = ct.ThermoPhase("pdss_hkft.yaml")
@@ -1268,8 +1281,8 @@ def test_vpss_and_hkft(self):
 
     def test_lattice_solid(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("Li7Si3_ls.xml"),
-            Path(self.test_work_dir).joinpath("Li7Si3_ls.yaml"),
+            self.test_data_path / "Li7Si3_ls.xml",
+            self.test_work_path / "Li7Si3_ls.yaml",
         )
         # Use ThermoPhase to avoid constructing a default Transport object which
         # throws an error for the LatticeSolidPhase
@@ -1283,8 +1296,8 @@ def test_lattice_solid(self):
 
     def test_margules(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("LiKCl_liquid.xml"),
-            Path(self.test_work_dir).joinpath("LiKCl_liquid.yaml"),
+            self.test_data_path / "LiKCl_liquid.xml",
+            self.test_work_path / "LiKCl_liquid.yaml",
         )
         ctmlPhase, yamlPhase = self.checkConversion("LiKCl_liquid")
         self.checkThermo(ctmlPhase, yamlPhase, [300, 500])
@@ -1292,8 +1305,8 @@ def test_margules(self):
     def test_idealsolidsoln(self):
         with self.assertWarnsRegex(UserWarning, "SolidKinetics type is not implemented"):
             ctml2yaml.convert(
-                Path(self.test_data_dir).joinpath("IdealSolidSolnPhaseExample.xml"),
-                Path(self.test_work_dir).joinpath("IdealSolidSolnPhaseExample.yaml"),
+                self.test_data_path / "IdealSolidSolnPhaseExample.xml",
+                self.test_work_path / "IdealSolidSolnPhaseExample.yaml",
             )
 
         # SolidKinetics is not implemented, so can't create a Kinetics class instance.
@@ -1307,8 +1320,8 @@ def test_idealsolidsoln(self):
 
     def test_idealmolalsoln(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("IdealMolalSolnPhaseExample.xml"),
-            Path(self.test_work_dir).joinpath("IdealMolalSolnPhaseExample.yaml"),
+            self.test_data_path / "IdealMolalSolnPhaseExample.xml",
+            self.test_work_path / "IdealMolalSolnPhaseExample.yaml",
         )
 
         ctmlPhase, yamlPhase = self.checkConversion("IdealMolalSolnPhaseExample")
@@ -1316,8 +1329,8 @@ def test_idealmolalsoln(self):
 
     def test_transport_models(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("transport_models_test.xml"),
-            Path(self.test_work_dir).joinpath("transport_models_test.yaml"),
+            self.test_data_path / "transport_models_test.xml",
+            self.test_work_path / "transport_models_test.yaml",
         )
         for name in ["UnityLewis", "CK_Mix", "CK_Multi", "HighP"]:
             ctmlPhase, yamlPhase = self.checkConversion("transport_models_test", name=name)
@@ -1325,8 +1338,8 @@ def test_transport_models(self):
 
     def test_nonreactant_orders(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("reaction-orders.xml"),
-            Path(self.test_work_dir).joinpath("reaction-orders.yaml"),
+            self.test_data_path / "reaction-orders.xml",
+            self.test_work_path / "reaction-orders.yaml",
         )
 
         ctmlPhase, yamlPhase = self.checkConversion("reaction-orders")
@@ -1335,8 +1348,8 @@ def test_nonreactant_orders(self):
 
     def test_species_ss_temperature_polynomials(self):
         ctml2yaml.convert(
-            Path(self.test_data_dir).joinpath("Li_Liquid.xml"),
-            Path(self.test_work_dir).joinpath("Li_Liquid.yaml"),
+            self.test_data_path / "Li_Liquid.xml",
+            self.test_work_path / "Li_Liquid.yaml",
         )
 
         ctmlPhase, yamlPhase = self.checkConversion("Li_Liquid")
@@ -1345,11 +1358,11 @@ def test_species_ss_temperature_polynomials(self):
     def test_duplicate_section_ids(self):
         with self.assertWarnsRegex(UserWarning, "Duplicate 'speciesData' id"):
                 ctml2yaml.convert(
-                    Path(self.test_data_dir).joinpath("duplicate-speciesData-ids.xml"),
-                    Path(self.test_work_dir).joinpath("duplicate-speciesData-ids.yaml")
+                    self.test_data_path / "duplicate-speciesData-ids.xml",
+                    self.test_work_path / "duplicate-speciesData-ids.yaml",
                 )
         with self.assertWarnsRegex(UserWarning, "Duplicate 'reactionData' id"):
                 ctml2yaml.convert(
-                    Path(self.test_data_dir).joinpath("duplicate-reactionData-ids.xml"),
-                    Path(self.test_work_dir).joinpath("duplicate-reactionData-ids.yaml")
+                    self.test_data_path / "duplicate-reactionData-ids.xml",
+                    self.test_work_path / "duplicate-reactionData-ids.yaml",
                 )
diff --git a/interfaces/cython/cantera/test/test_equilibrium.py b/interfaces/cython/cantera/test/test_equilibrium.py
index eea5cbb76ff..f0a236e580b 100644
--- a/interfaces/cython/cantera/test/test_equilibrium.py
+++ b/interfaces/cython/cantera/test/test_equilibrium.py
@@ -1,5 +1,4 @@
 import unittest
-from os.path import join as pjoin
 
 import numpy as np
 
@@ -153,7 +152,7 @@ def test_equil_TP(self):
 
             data[i,1:] = self.mix.species_moles
 
-        self.compare(data, pjoin(self.test_data_dir, 'koh-equil-TP.csv'))
+        self.compare(data, self.test_data_path / "koh-equil-TP.csv")
 
     @utilities.slow_test
     def test_equil_HP(self):
@@ -177,7 +176,7 @@ def test_equil_HP(self):
             data[i,1] = self.mix.T # equilibrated temperature
             data[i,2:] = self.mix.species_moles
 
-        self.compare(data, pjoin(self.test_data_dir, 'koh-equil-HP.csv'))
+        self.compare(data, self.test_data_path / "koh-equil-HP.csv")
 
 
 class TestEquil_GasCarbon(utilities.CanteraTest):
@@ -207,7 +206,7 @@ def solve(self, solver, **kwargs):
             data[i,:2] = (phi[i], mix.T)
             data[i,2:] = mix.species_moles
 
-        self.compare(data, pjoin(self.test_data_dir, 'gas-carbon-equil.csv'))
+        self.compare(data, self.test_data_path / "gas-carbon-equil.csv")
 
     @utilities.slow_test
     def test_gibbs(self):
diff --git a/interfaces/cython/cantera/test/test_func1.py b/interfaces/cython/cantera/test/test_func1.py
index 3efa0a2e324..dd91a5f32f4 100644
--- a/interfaces/cython/cantera/test/test_func1.py
+++ b/interfaces/cython/cantera/test/test_func1.py
@@ -2,7 +2,6 @@
 
 import cantera as ct
 from . import utilities
-from .utilities import unittest
 
 class TestFunc1(utilities.CanteraTest):
     def test_function(self):
diff --git a/interfaces/cython/cantera/test/test_kinetics.py b/interfaces/cython/cantera/test/test_kinetics.py
index 55000f3c039..a5e035ec8c1 100644
--- a/interfaces/cython/cantera/test/test_kinetics.py
+++ b/interfaces/cython/cantera/test/test_kinetics.py
@@ -1,8 +1,6 @@
 import numpy as np
 import re
 import itertools
-from os.path import join as pjoin
-import os
 
 import cantera as ct
 from . import utilities
@@ -816,7 +814,7 @@ def cathode_curr(E):
                              cathode_bulk.electric_potential -
                              anode_bulk.electric_potential])
 
-        self.compare(data, pjoin(self.test_data_dir, 'sofc-test.csv'), rtol=1e-7)
+        self.compare(data, self.test_data_path / "sofc-test.csv", rtol=1e-7)
 
 
 class TestDuplicateReactions(utilities.CanteraTest):
@@ -889,8 +887,7 @@ def test_fromCti(self):
 
     def test_fromXml(self):
         import xml.etree.ElementTree as ET
-        p = os.path.dirname(__file__)
-        root = ET.parse(pjoin(p, '..', 'data', 'h2o2.xml')).getroot()
+        root = ET.parse(self.cantera_data_path / "h2o2.xml").getroot()
         rxn_node = root.find('.//reaction[@id="0001"]')
         r = ct.Reaction.fromXml(ET.tostring(rxn_node))
 
@@ -925,18 +922,14 @@ def test_listFromFile(self):
 
     def test_listFromCti(self):
         gas = ct.Solution("h2o2.xml", transport_model=None)
-        p = os.path.dirname(__file__)
-        with open(pjoin(p, '..', 'data', 'h2o2.cti')) as f:
-            R = ct.Reaction.listFromCti(f.read())
+        R = ct.Reaction.listFromCti((self.cantera_data_path / "h2o2.cti").read_text())
         eq1 = [r.equation for r in R]
         eq2 = [r.equation for r in gas.reactions()]
         self.assertEqual(eq1, eq2)
 
     def test_listFromXml(self):
         gas = ct.Solution("h2o2.xml", transport_model=None)
-        p = os.path.dirname(__file__)
-        with open(pjoin(p, '..', 'data', 'h2o2.xml')) as f:
-            R = ct.Reaction.listFromXml(f.read())
+        R = ct.Reaction.listFromXml((self.cantera_data_path / "h2o2.xml").read_text())
         eq1 = [r.equation for r in R]
         eq2 = [r.equation for r in gas.reactions()]
         self.assertEqual(eq1, eq2)
diff --git a/interfaces/cython/cantera/test/test_onedim.py b/interfaces/cython/cantera/test/test_onedim.py
index 753ce16a3e5..5cc10f45315 100644
--- a/interfaces/cython/cantera/test/test_onedim.py
+++ b/interfaces/cython/cantera/test/test_onedim.py
@@ -1,8 +1,6 @@
 import cantera as ct
 from . import utilities
 import numpy as np
-import os
-from os.path import join as pjoin
 
 from cantera.composite import _h5py
 
@@ -510,9 +508,10 @@ def test_save_restore(self):
 
         self.create_sim(p, Tin, reactants)
         self.solve_fixed_T()
-        filename = pjoin(self.test_work_dir, 'onedim-fixed-T.xml')
-        if os.path.exists(filename):
-            os.remove(filename)
+        filename = self.test_work_path / "onedim-fixed-T.xml"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if filename.is_file():
+            filename.unlink()
 
         Y1 = self.sim.Y
         u1 = self.sim.velocity
@@ -577,9 +576,10 @@ def test_save_restore_add_species(self):
         p = 2 * ct.one_atm
         Tin = 400
 
-        filename = pjoin(self.test_work_dir, 'onedim-add-species.xml')
-        if os.path.exists(filename):
-            os.remove(filename)
+        filename = self.test_work_path / "onedim-add-species.xml"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if filename.is_file():
+            filename.unlink()
 
         self.create_sim(p, Tin, reactants, mech='h2o2.xml')
         gas1 = self.gas
@@ -606,9 +606,10 @@ def test_save_restore_remove_species(self):
         p = 2 * ct.one_atm
         Tin = 400
 
-        filename = pjoin(self.test_work_dir, 'onedim-add-species.xml')
-        if os.path.exists(filename):
-            os.remove(filename)
+        filename = self.test_work_path / "onedim-add-species.xml"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if filename.is_file():
+            filename.unlink()
 
         self.create_sim(p, Tin, reactants, mech='h2o2-plus.xml')
         gas1 = self.gas
@@ -630,9 +631,10 @@ def test_save_restore_remove_species(self):
             self.assertArrayNear(Y1[k1], Y2[k2])
 
     def test_write_csv(self):
-        filename = pjoin(self.test_work_dir, 'onedim-write_csv.csv')
-        if os.path.exists(filename):
-            os.remove(filename)
+        filename = self.test_work_path / "onedim-write_csv.csv"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if filename.is_file():
+            filename.unlink()
 
         self.create_sim(2e5, 350, 'H2:1.0, O2:2.0', mech='h2o2.xml')
         self.sim.write_csv(filename)
@@ -645,9 +647,10 @@ def test_write_csv(self):
 
     @utilities.unittest.skipIf(isinstance(_h5py, ImportError), "h5py is not installed")
     def test_write_hdf(self):
-        filename = pjoin(self.test_work_dir, 'onedim-write_hdf.h5')
-        if os.path.exists(filename):
-            os.remove(filename)
+        filename = self.test_work_path / "onedim-write_hdf.h5"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if filename.is_file():
+            filename.unlink()
 
         self.run_mix(phi=1.1, T=350, width=2.0, p=2.0, refine=False)
         desc = 'mixture-averaged simulation'
@@ -771,7 +774,7 @@ def solve_mix(self, ratio=3.0, slope=0.1, curve=0.12, prune=0.0):
 
     @utilities.slow_test
     def test_mixture_averaged(self, saveReference=False):
-        referenceFile = pjoin(self.test_data_dir, 'DiffusionFlameTest-h2-mix.csv')
+        referenceFile = self.test_data_path / "DiffusionFlameTest-h2-mix.csv"
         self.create_sim(p=ct.one_atm)
 
         nPoints = len(self.sim.grid)
@@ -796,7 +799,7 @@ def test_mixture_averaged(self, saveReference=False):
             self.assertFalse(bad, bad)
 
     def test_auto(self, saveReference=False):
-        referenceFile = pjoin(self.test_data_dir, 'DiffusionFlameTest-h2-auto.csv')
+        referenceFile = self.test_data_path / "DiffusionFlameTest-h2-auto.csv"
         self.create_sim(p=ct.one_atm, mdot_fuel=2, mdot_ox=3)
 
         nPoints = []
@@ -885,7 +888,7 @@ def test_restart(self):
         self.assertNear(mdot[-1], -self.sim.oxidizer_inlet.mdot, 1e-4)
 
     def test_mixture_averaged_rad(self, saveReference=False):
-        referenceFile = pjoin(self.test_data_dir, 'DiffusionFlameTest-h2-mix-rad.csv')
+        referenceFile = self.test_data_path / "DiffusionFlameTest-h2-mix-rad.csv"
         self.create_sim(p=ct.one_atm)
 
         nPoints = len(self.sim.grid)
@@ -916,12 +919,15 @@ def test_mixture_averaged_rad(self, saveReference=False):
                                             rtol=1e-2, atol=1e-8, xtol=1e-2)
             self.assertFalse(bad, bad)
 
-        filename = pjoin(self.test_work_dir, 'DiffusionFlameTest-h2-mix-rad.csv')
+        filename = self.test_work_path / "DiffusionFlameTest-h2-mix-rad.csv"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if filename.is_file():
+            filename.unlink()
+
         self.sim.write_csv(filename) # check output
-        self.assertTrue(os.path.exists(filename))
+        self.assertTrue(filename.is_file())
         csv_data = np.genfromtxt(filename, dtype=float, delimiter=',', names=True)
         self.assertIn('qdot', csv_data.dtype.names)
-        os.remove(filename)
 
     def test_strain_rate(self):
         # This doesn't test that the values are correct, just that they can be
@@ -1006,7 +1012,7 @@ def test_mixture_averaged(self, saveReference=False):
         data[:,3] = sim.T
         data[:,4:] = sim.Y.T
 
-        referenceFile = pjoin(self.test_data_dir, 'CounterflowPremixedFlame-h2-mix.csv')
+        referenceFile = self.test_data_path / "CounterflowPremixedFlame-h2-mix.csv"
         if saveReference:
             np.savetxt(referenceFile, data, '%11.6e', ', ')
         else:
@@ -1014,12 +1020,15 @@ def test_mixture_averaged(self, saveReference=False):
                                             rtol=1e-2, atol=1e-8, xtol=1e-2)
             self.assertFalse(bad, bad)
 
-        filename = pjoin(self.test_work_dir, 'CounterflowPremixedFlame-h2-mix.csv')
+        filename = self.test_work_path / "CounterflowPremixedFlame-h2-mix.csv"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if filename.is_file():
+            filename.unlink()
+
         sim.write_csv(filename) # check output
-        self.assertTrue(os.path.exists(filename))
+        self.assertTrue(filename.is_file())
         csv_data = np.genfromtxt(filename, dtype=float, delimiter=',', names=True)
         self.assertNotIn('qdot', csv_data.dtype.names)
-        os.remove(filename)
 
     def run_case(self, phi, T, width, P):
         gas = ct.Solution('h2o2.xml')
@@ -1190,9 +1199,10 @@ def test_reacting_surface_case3(self):
 
     @utilities.unittest.skipIf(isinstance(_h5py, ImportError), "h5py is not installed")
     def test_write_hdf(self):
-        filename = pjoin(self.test_work_dir, 'impingingjet-write_hdf.h5')
-        if os.path.exists(filename):
-            os.remove(filename)
+        filename = self.test_work_path / "impingingjet-write_hdf.h5"
+        # In Python >= 3.8, this can be replaced by the missing_ok argument
+        if filename.is_file():
+            filename.unlink()
 
         self.run_reacting_surface(xch4=0.095, tsurf=900.0, mdot=0.06, width=0.1)
         self.sim.write_hdf(filename)
diff --git a/interfaces/cython/cantera/test/test_purefluid.py b/interfaces/cython/cantera/test/test_purefluid.py
index 9f1ee9bbb83..b2e4a73f990 100644
--- a/interfaces/cython/cantera/test/test_purefluid.py
+++ b/interfaces/cython/cantera/test/test_purefluid.py
@@ -1,6 +1,5 @@
 import itertools
 import numpy as np
-import warnings
 
 import cantera as ct
 from . import utilities
diff --git a/interfaces/cython/cantera/test/test_reactor.py b/interfaces/cython/cantera/test/test_reactor.py
index 7ca13a34404..67a5e784827 100644
--- a/interfaces/cython/cantera/test/test_reactor.py
+++ b/interfaces/cython/cantera/test/test_reactor.py
@@ -1,7 +1,5 @@
 import math
 import re
-from os.path import join as pjoin
-import os
 
 import numpy as np
 from .utilities import unittest
@@ -9,8 +7,6 @@
 import cantera as ct
 from . import utilities
 
-import warnings
-
 class TestReactor(utilities.CanteraTest):
     reactorClass = ct.Reactor
 
@@ -1145,8 +1141,8 @@ def test_coverages_regression1(self):
         surf1.coverages = C
         self.assertArrayNear(surf1.coverages, C)
         data = []
-        test_file = pjoin(self.test_work_dir, 'test_coverages_regression1.csv')
-        reference_file = pjoin(self.test_data_dir, 'WallKinetics-coverages-regression1.csv')
+        test_file = self.test_work_path / "test_coverages_regression1.csv"
+        reference_file = self.test_data_path / "WallKinetics-coverages-regression1.csv"
         data = []
         for t in np.linspace(1e-6, 1e-3):
             self.net.advance(t)
@@ -1170,8 +1166,8 @@ def test_coverages_regression2(self):
         surf.coverages = C
         self.assertArrayNear(surf.coverages, C)
         data = []
-        test_file = pjoin(self.test_work_dir, 'test_coverages_regression2.csv')
-        reference_file = pjoin(self.test_data_dir, 'WallKinetics-coverages-regression2.csv')
+        test_file = self.test_work_path / "test_coverages_regression2.csv"
+        reference_file = self.test_data_path / "WallKinetics-coverages-regression2.csv"
         data = []
         for t in np.linspace(1e-6, 1e-3):
             self.net.advance(t)
@@ -1516,7 +1512,7 @@ class CombustorTestImplementation:
     """
 
     def setUp(self):
-        self.referenceFile = pjoin(os.path.dirname(__file__), 'data', 'CombustorTest-integrateWithAdvance.csv')
+        self.referenceFile = utilities.TEST_DATA_PATH / "CombustorTest-integrateWithAdvance.csv"
         self.gas = ct.Solution('h2o2.yaml', transport_model=None)
 
         # create a reservoir for the fuel inlet, and set to pure methane.
@@ -1622,7 +1618,7 @@ class WallTestImplementation:
     """
 
     def setUp(self):
-        self.referenceFile = pjoin(os.path.dirname(__file__), 'data', 'WallTest-integrateWithAdvance.csv')
+        self.referenceFile = utilities.TEST_DATA_PATH / "WallTest-integrateWithAdvance.csv"
         # reservoir to represent the environment
         self.gas0 = ct.Solution('air.xml')
         self.gas0.TP = 300, ct.one_atm
diff --git a/interfaces/cython/cantera/test/test_thermo.py b/interfaces/cython/cantera/test/test_thermo.py
index b7b34349b6b..6d5cbcd9a77 100644
--- a/interfaces/cython/cantera/test/test_thermo.py
+++ b/interfaces/cython/cantera/test/test_thermo.py
@@ -1,10 +1,6 @@
-from os.path import join as pjoin
-from pathlib import Path
 from collections import OrderedDict
-import os
 import numpy as np
 import gc
-import warnings
 
 import cantera as ct
 from . import utilities
@@ -1113,8 +1109,7 @@ def test_fromCti(self):
 
     def test_fromXml(self):
         import xml.etree.ElementTree as ET
-        p = os.path.dirname(__file__)
-        root = ET.parse(pjoin(p, '..', 'data', 'h2o2.xml')).getroot()
+        root = ET.parse(self.cantera_data_path / "h2o2.xml").getroot()
         h2_node = root.find('.//species[@name="H2"]')
         h2_string = ET.tostring(h2_node)
 
@@ -1138,10 +1133,7 @@ def test_listfromFile_yaml(self):
         self.assertEqual({sp.name for sp in S}, set(self.gas.species_names))
 
     def test_listFromCti(self):
-        p = os.path.dirname(__file__)
-        with open(pjoin(p, '..', 'data', 'h2o2.cti')) as f:
-            S = ct.Species.listFromCti(f.read())
-
+        S = ct.Species.listFromCti((self.cantera_data_path / "h2o2.cti").read_text())
         self.assertEqual(S[3].name, self.gas.species_name(3))
 
     def test_listFomYaml(self):
@@ -1160,17 +1152,14 @@ def test_listFomYaml(self):
 
     def test_listFromYaml_section(self):
         species = ct.Species.listFromYaml(
-            Path(__file__).parent.joinpath('data', 'ideal-gas.yaml').read_text(),
+            (self.test_data_path / "ideal-gas.yaml").read_text(),
             'species')
 
         self.assertEqual(species[0].name, 'O2')
         self.assertEqual(species[1].composition, {'N': 1, 'O': 1})
 
     def test_listFromXml(self):
-        p = os.path.dirname(__file__)
-        with open(pjoin(p, '..', 'data', 'h2o2.xml')) as f:
-            S = ct.Species.listFromXml(f.read())
-
+        S = ct.Species.listFromXml((self.cantera_data_path / "h2o2.xml").read_text())
         self.assertEqual(S[4].name, self.gas.species_name(4))
 
     def test_modify_thermo(self):
diff --git a/interfaces/cython/cantera/test/utilities.py b/interfaces/cython/cantera/test/utilities.py
index cbb0bebb6d2..3a10a07120c 100644
--- a/interfaces/cython/cantera/test/utilities.py
+++ b/interfaces/cython/cantera/test/utilities.py
@@ -1,14 +1,29 @@
 import numpy as np
-import sys
-import os
+from os import environ
 import warnings
-import shutil
 import tempfile
 import unittest
-import errno
+from pathlib import Path, PurePath
+
+try:
+    import ruamel_yaml as yaml
+except ImportError:
+    from ruamel import yaml
+
 import cantera
 
-slow_test = unittest.skipIf(os.environ.get("CT_SKIP_SLOW", "0") == "1", "slow test")
+slow_test = unittest.skipIf(environ.get("CT_SKIP_SLOW", "0") == "1", "slow test")
+
+TEST_DATA_PATH = Path(__file__).parent / "data"
+CANTERA_DATA_PATH = Path(__file__).parents[1] / "data"
+
+
+def load_yaml(yml_file, typ="safe"):
+    # Load YAML data from file. The YAML loader defaults to "safe".
+    yaml_ = yaml.YAML(typ=typ)
+    with open(yml_file, "rt", encoding="utf-8") as stream:
+        return yaml_.load(stream)
+
 
 class CanteraTest(unittest.TestCase):
     @classmethod
@@ -17,37 +32,34 @@ def setUpClass(cls):
         # an in-source test, create the directory in the root
         # test/work directory. Otherwise, create a system level
         # temporary directory
-        root_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
-                                                '..', '..', '..', '..'))
-        if os.path.exists(os.path.join(root_dir, 'SConstruct')):
-            cls.test_work_dir = os.path.join(root_dir, 'test', 'work', 'python')
+        root_dir = Path(__file__).parents[4].resolve()
+        if (root_dir / "SConstruct").is_file():
+            cls.test_work_path = root_dir / "test" / "work" / "python"
             cls.using_tempfile = False
             try:
-                os.makedirs(cls.test_work_dir)
-            except OSError as e:
-                if e.errno == errno.EEXIST:
-                    pass
-                elif e.errno == errno.EACCES:
-                    cls.test_work_dir = tempfile.mkdtemp()
-                else:
-                    raise
+                cls.test_work_path.mkdir(exist_ok=True)
+            except FileNotFoundError:
+                cls.test_work_path = Path(tempfile.mkdtemp())
+                cls.using_tempfile = True
         else:
-            cls.test_work_dir = tempfile.mkdtemp()
+            cls.test_work_path = Path(tempfile.mkdtemp())
             cls.using_tempfile = True
 
         cantera.make_deprecation_warnings_fatal()
-        cantera.add_directory(cls.test_work_dir)
-        cls.test_data_dir = os.path.abspath(os.path.join(os.path.dirname(__file__), 'data'))
-        cls.cantera_data = os.path.abspath(os.path.join(
-            os.path.dirname(__file__), '..', 'data'))
+        cantera.add_directory(cls.test_work_path)
+        cls.test_data_path = TEST_DATA_PATH
+        cls.cantera_data_path = CANTERA_DATA_PATH
+
 
     @classmethod
     def tearDownClass(cls):
         # Remove the working directory after testing, but only if its a temp directory
         if getattr(cls, "using_tempfile", False):
             try:
-                shutil.rmtree(cls.test_work_dir)
-            except OSError:
+                for f in cls.test_work_path.glob("*.*"):
+                    f.unlink()
+                cls.test_work_path.rmdir()
+            except FileNotFoundError:
                 pass
 
     def assertNear(self, a, b, rtol=1e-8, atol=1e-12, msg=None):
@@ -87,7 +99,7 @@ def compare(self, data, reference_file, rtol=1e-8, atol=1e-12):
         file if it does not exist.
         """
         data = np.array(data)
-        if os.path.exists(reference_file):
+        if Path(reference_file).is_file():
             # Compare with existing output file
             ref = np.genfromtxt(reference_file)
             self.assertEqual(data.shape, ref.shape)
@@ -96,7 +108,7 @@ def compare(self, data, reference_file, rtol=1e-8, atol=1e-12):
         else:
             # Generate the output file for the first time
             warnings.warn('Generating test data file:' +
-                          os.path.abspath(reference_file))
+                          Path(reference_file).resolve())
             np.savetxt(reference_file, data, fmt='%.10e')
 
 
@@ -117,12 +129,12 @@ def compareProfiles(reference, sample, rtol=1e-5, atol=1e-12, xtol=1e-5):
     If the comparison succeeds, this function returns `None`. If the comparison
     fails, a formatted report of the differing elements is returned.
     """
-    if isinstance(reference, str):
+    if isinstance(reference, (str, PurePath)):
         reference = np.genfromtxt(reference, delimiter=',').T
     else:
         reference = np.asarray(reference).T
 
-    if isinstance(sample, str):
+    if isinstance(sample, (str, PurePath)):
         sample = np.genfromtxt(sample, delimiter=',').T
     else:
         sample = np.asarray(sample).T
diff --git a/interfaces/cython/cantera/utils.pyx b/interfaces/cython/cantera/utils.pyx
index 79b91e330cf..7388f55d81f 100644
--- a/interfaces/cython/cantera/utils.pyx
+++ b/interfaces/cython/cantera/utils.pyx
@@ -23,7 +23,7 @@ cdef pystr(string x):
 
 def add_directory(directory):
     """ Add a directory to search for Cantera data files. """
-    CxxAddDirectory(stringify(directory))
+    CxxAddDirectory(stringify(str(directory)))
 
 def get_data_directories():
     """ Get a list of the directories Cantera searches for data files. """