diff --git a/jedi/_compatibility.py b/jedi/_compatibility.py
index 38b701e3..6bb3eeaa 100644
--- a/jedi/_compatibility.py
+++ b/jedi/_compatibility.py
@@ -20,7 +20,7 @@ def cast_path(string):
     """
     if isinstance(string, bytes):
         return str(string, encoding='UTF-8', errors='replace')
-    return string
+    return str(string)
 
 
 def pickle_load(file):
diff --git a/jedi/api/__init__.py b/jedi/api/__init__.py
index a2098bef..2be38b8f 100644
--- a/jedi/api/__init__.py
+++ b/jedi/api/__init__.py
@@ -142,7 +142,7 @@ class Script(object):
 
         if project is None:
             # Load the Python grammar of the current interpreter.
-            project = get_default_project(self.path)
+            project = get_default_project(None if self.path is None else self.path.parent)
         # TODO deprecate and remove sys_path from the Script API.
         if sys_path is not None:
             project._sys_path = sys_path
@@ -192,7 +192,7 @@ class Script(object):
             file_io = None
         else:
             file_io = KnownContentFileIO(cast_path(self.path), self._code)
-        if self.path is not None and self.path.suffix == 'pyi':
+        if self.path is not None and self.path.suffix == '.pyi':
             # We are in a stub file. Try to load the stub properly.
             stub_module = load_proper_stub_module(
                 self._inference_state,
diff --git a/jedi/api/classes.py b/jedi/api/classes.py
index 455d2b6a..c55d7b68 100644
--- a/jedi/api/classes.py
+++ b/jedi/api/classes.py
@@ -15,6 +15,7 @@ the interesting information about all operations.
 """
 import re
 import warnings
+from typing import Optional
 
 from parso.python.tree import search_ancestor
 
@@ -92,7 +93,7 @@ class BaseName(object):
         return self._name.get_root_context()
 
     @property
-    def module_path(self):
+    def module_path(self) -> Optional[str]:
         """
         Shows the file path of a module. e.g. ``/usr/lib/python3.9/os.py``
 
@@ -102,7 +103,9 @@ class BaseName(object):
         if module.is_stub() or not module.is_compiled():
             # Compiled modules should not return a module path even if they
             # have one.
-            return self._get_module_context().py__file__()
+            path = self._get_module_context().py__file__()
+            if path is not None:
+                return path
 
         return None
 
diff --git a/jedi/api/helpers.py b/jedi/api/helpers.py
index 7d3677f7..bcd59922 100644
--- a/jedi/api/helpers.py
+++ b/jedi/api/helpers.py
@@ -44,7 +44,7 @@ def match(string, like_name, fuzzy=False):
 
 def sorted_definitions(defs):
     # Note: `or ''` below is required because `module_path` could be
-    return sorted(defs, key=lambda x: (str(x.module_path) or '',
+    return sorted(defs, key=lambda x: (str(x.module_path or ''),
                                        x.line or 0,
                                        x.column or 0,
                                        x.name))
diff --git a/jedi/api/project.py b/jedi/api/project.py
index 056a3873..ae00c38b 100644
--- a/jedi/api/project.py
+++ b/jedi/api/project.py
@@ -80,6 +80,8 @@ class Project(object):
 
         :param path: The path of the directory you want to use as a project.
         """
+        if isinstance(path, str):
+            path = Path(path)
         with open(cls._get_json_path(path)) as f:
             version, data = json.load(f)
 
@@ -98,8 +100,9 @@ class Project(object):
         data.pop('_environment', None)
         data.pop('_django', None)  # TODO make django setting public?
         data = {k.lstrip('_'): v for k, v in data.items()}
+        data['path'] = str(data['path'])
 
-        self._path.mkdir(parents=True, exist_ok=True)
+        self._get_config_folder_path(self._path).mkdir(parents=True, exist_ok=True)
         with open(self._get_json_path(self._path), 'w') as f:
             return json.dump((_SERIALIZER_VERSION, data), f)
 
@@ -129,11 +132,15 @@ class Project(object):
             self._path = path
 
             self._environment_path = environment_path
+            if sys_path is not None:
+                # Remap potential pathlib.Path entries
+                sys_path = list(map(str, sys_path))
             self._sys_path = sys_path
             self._smart_sys_path = smart_sys_path
             self._load_unsafe_extensions = load_unsafe_extensions
             self._django = False
-            self.added_sys_path = list(added_sys_path)
+            # Remap potential pathlib.Path entries
+            self.added_sys_path = list(map(str, added_sys_path))
             """The sys path that is going to be added at the end of the """
 
         py2_comp(path, **kwargs)
@@ -173,10 +180,10 @@ class Project(object):
             prefixed.append(str(self._path))
 
             if inference_state.script_path is not None:
-                suffixed += discover_buildout_paths(
+                suffixed += map(str, discover_buildout_paths(
                     inference_state,
                     inference_state.script_path
-                )
+                ))
 
                 if add_parent_paths:
                     # Collect directories in upward search by:
@@ -362,6 +369,8 @@ def get_default_project(path=None):
     """
     if path is None:
         path = Path.cwd()
+    elif isinstance(path, str):
+        path = Path(path)
 
     check = path.absolute()
     probable_path = None
@@ -379,7 +388,7 @@ def get_default_project(path=None):
                 # In the case that a __init__.py exists, it's in 99% just a
                 # Python package and the project sits at least one level above.
                 continue
-            else:
+            elif not dir.is_file():
                 first_no_init_file = dir
 
         if _is_django_path(dir):
diff --git a/jedi/api/refactoring/__init__.py b/jedi/api/refactoring/__init__.py
index e73beee4..32aff1ed 100644
--- a/jedi/api/refactoring/__init__.py
+++ b/jedi/api/refactoring/__init__.py
@@ -1,4 +1,6 @@
 import difflib
+from pathlib import Path
+from typing import Dict
 
 from parso import split_lines
 
@@ -47,8 +49,8 @@ class ChangedFile(object):
             to_p = self._to_path.relative_to(project_path)
         diff = difflib.unified_diff(
             old_lines, new_lines,
-            fromfile=from_p,
-            tofile=to_p,
+            fromfile=str(from_p),
+            tofile=str(to_p),
         )
         # Apparently there's a space at the end of the diff - for whatever
         # reason.
@@ -76,17 +78,15 @@ class Refactoring(object):
         self._renames = renames
         self._file_to_node_changes = file_to_node_changes
 
-    def get_changed_files(self):
-        """
-        Returns a path to ``ChangedFile`` map.
-        """
+    def get_changed_files(self) -> Dict[Path, ChangedFile]:
         def calculate_to_path(p):
             if p is None:
                 return p
+            p = str(p)
             for from_, to in renames:
-                if p.startswith(from_):
-                    p = to + p[len(from_):]
-            return p
+                if p.startswith(str(from_)):
+                    p = str(to) + p[len(str(from_)):]
+            return Path(p)
 
         renames = self.get_renames()
         return {
@@ -144,7 +144,8 @@ def rename(inference_state, definitions, new_name):
     for d in definitions:
         tree_name = d._name.tree_name
         if d.type == 'module' and tree_name is None:
-            file_renames.add(_calculate_rename(d.module_path, new_name))
+            p = None if d.module_path is None else Path(d.module_path)
+            file_renames.add(_calculate_rename(p, new_name))
         else:
             # This private access is ok in a way. It's not public to
             # protect Jedi users from seeing it.
diff --git a/jedi/inference/compiled/value.py b/jedi/inference/compiled/value.py
index d3d6f4a0..61600983 100644
--- a/jedi/inference/compiled/value.py
+++ b/jedi/inference/compiled/value.py
@@ -4,6 +4,7 @@ Imitate the parser representation.
 import re
 from functools import partial
 from inspect import Parameter
+from pathlib import Path
 
 from jedi import debug
 from jedi.inference.utils import to_list
@@ -312,7 +313,10 @@ class CompiledModule(CompiledValue):
         return tuple(name.split('.'))
 
     def py__file__(self):
-        return cast_path(self.access_handle.py__file__())
+        path = cast_path(self.access_handle.py__file__())
+        if path is None:
+            return None
+        return Path(path)
 
 
 class CompiledName(AbstractNameDefinition):
diff --git a/jedi/inference/gradual/typeshed.py b/jedi/inference/gradual/typeshed.py
index 10681834..e186bfc3 100644
--- a/jedi/inference/gradual/typeshed.py
+++ b/jedi/inference/gradual/typeshed.py
@@ -2,6 +2,7 @@ import os
 import re
 from functools import wraps
 from collections import namedtuple
+from pathlib import Path
 
 from jedi import settings
 from jedi.file_io import FileIO
@@ -11,10 +12,10 @@ from jedi.inference.base_value import ValueSet, NO_VALUES
 from jedi.inference.gradual.stub_value import TypingModuleWrapper, StubModuleValue
 from jedi.inference.value import ModuleValue
 
-_jedi_path = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
-TYPESHED_PATH = os.path.join(_jedi_path, 'third_party', 'typeshed')
-DJANGO_INIT_PATH = os.path.join(_jedi_path, 'third_party', 'django-stubs',
-                                'django-stubs', '__init__.pyi')
+_jedi_path = Path(__file__).parent.parent.parent
+TYPESHED_PATH = _jedi_path.joinpath('third_party', 'typeshed')
+DJANGO_INIT_PATH = _jedi_path.joinpath('third_party', 'django-stubs',
+                                       'django-stubs', '__init__.pyi')
 
 _IMPORT_MAP = dict(
     _collections='collections',
@@ -60,7 +61,7 @@ def _create_stub_map(directory_path_info):
 def _get_typeshed_directories(version_info):
     check_version_list = ['2and3', '3']
     for base in ['stdlib', 'third_party']:
-        base_path = os.path.join(TYPESHED_PATH, base)
+        base_path = TYPESHED_PATH.joinpath(base)
         base_list = os.listdir(base_path)
         for base_list_entry in base_list:
             match = re.match(r'(\d+)\.(\d+)$', base_list_entry)
@@ -70,7 +71,7 @@ def _get_typeshed_directories(version_info):
 
         for check_version in check_version_list:
             is_third_party = base != 'stdlib'
-            yield PathInfo(os.path.join(base_path, check_version), is_third_party)
+            yield PathInfo(str(base_path.joinpath(check_version)), is_third_party)
 
 
 _version_cache = {}
@@ -181,7 +182,7 @@ def _try_to_load_stub(inference_state, import_names, python_value_set,
             return _try_to_load_stub_from_file(
                 inference_state,
                 python_value_set,
-                file_io=FileIO(DJANGO_INIT_PATH),
+                file_io=FileIO(str(DJANGO_INIT_PATH)),
                 import_names=import_names,
             )
 
diff --git a/jedi/inference/gradual/utils.py b/jedi/inference/gradual/utils.py
index fc68b7b1..83162625 100644
--- a/jedi/inference/gradual/utils.py
+++ b/jedi/inference/gradual/utils.py
@@ -1,4 +1,5 @@
 import os
+from pathlib import Path
 
 from jedi.inference.gradual.typeshed import TYPESHED_PATH, create_stub_module
 
@@ -9,14 +10,18 @@ def load_proper_stub_module(inference_state, file_io, import_names, module_node)
     module.
     """
     path = file_io.path
-    assert path.endswith('.pyi')
-    if path.startswith(TYPESHED_PATH):
-        # /foo/stdlib/3/os/__init__.pyi -> stdlib/3/os/__init__
-        rest = path[len(TYPESHED_PATH) + 1: -4]
-        split_paths = tuple(rest.split(os.path.sep))
+    path = Path(path)
+    assert path.suffix == '.pyi'
+    try:
+        relative_path = path.relative_to(TYPESHED_PATH)
+    except ValueError:
+        pass
+    else:
+        # /[...]/stdlib/3/os/__init__.pyi -> stdlib/3/os/__init__
+        rest = relative_path.with_suffix('')
         # Remove the stdlib/3 or third_party/3.6 part
-        import_names = split_paths[2:]
-        if import_names[-1] == '__init__':
+        import_names = rest.parts[2:]
+        if rest.name == '__init__':
             import_names = import_names[:-1]
 
     if import_names is not None:
diff --git a/jedi/inference/sys_path.py b/jedi/inference/sys_path.py
index 12e0f166..bc91d56d 100644
--- a/jedi/inference/sys_path.py
+++ b/jedi/inference/sys_path.py
@@ -148,7 +148,7 @@ def discover_buildout_paths(inference_state, script_path):
 
 
 def _get_paths_from_buildout_script(inference_state, buildout_script_path):
-    file_io = FileIO(buildout_script_path)
+    file_io = FileIO(str(buildout_script_path))
     try:
         module_node = inference_state.parse(
             file_io=file_io,
@@ -164,7 +164,7 @@ def _get_paths_from_buildout_script(inference_state, buildout_script_path):
         inference_state, module_node,
         file_io=file_io,
         string_names=None,
-        code_lines=get_cached_code_lines(inference_state.grammar, buildout_script_path),
+        code_lines=get_cached_code_lines(inference_state.grammar, str(buildout_script_path)),
     ).as_context()
     for path in check_sys_path_modifications(module_context):
         yield path
@@ -228,6 +228,8 @@ def transform_path_to_dotted(sys_path, module_path):
     """
     # First remove the suffix.
     module_path = remove_python_path_suffix(module_path)
+    if module_path.name.startswith('.'):
+        return None, False
 
     # Once the suffix was removed we are using the files as we know them. This
     # means that if someone uses an ending like .vim for a Python file, .vim
diff --git a/jedi/plugins/pytest.py b/jedi/plugins/pytest.py
index 91a85c2f..432385e3 100644
--- a/jedi/plugins/pytest.py
+++ b/jedi/plugins/pytest.py
@@ -1,3 +1,5 @@
+from pathlib import Path
+
 from parso.python.tree import search_ancestor
 from jedi.inference.cache import inference_state_method_cache
 from jedi.inference.imports import load_module_from_path
@@ -128,7 +130,7 @@ def _iter_pytest_modules(module_context, skip_own_module=False):
         sys_path = module_context.inference_state.get_sys_path()
         while any(folder.path.startswith(p) for p in sys_path):
             file_io = folder.get_file_io('conftest.py')
-            if file_io.path != module_context.py__file__():
+            if Path(file_io.path) != module_context.py__file__():
                 try:
                     m = load_module_from_path(module_context.inference_state, file_io)
                     yield m.as_context()
diff --git a/test/helpers.py b/test/helpers.py
index e9426eba..b11f4941 100644
--- a/test/helpers.py
+++ b/test/helpers.py
@@ -7,14 +7,14 @@ from contextlib import contextmanager
 
 import os
 import pytest
-from os.path import abspath, dirname, join
 from functools import partial, wraps
 from jedi import Project
+from pathlib import Path
 
-test_dir = dirname(abspath(__file__))
+test_dir = Path(__file__).absolute().parent
 test_dir_project = Project(test_dir)
-root_dir = dirname(test_dir)
-example_dir = join(test_dir, 'examples')
+root_dir = test_dir.parent
+example_dir = test_dir.joinpath('examples')
 
 sample_int = 1  # This is used in completion/imports.py
 
@@ -25,7 +25,7 @@ skip_if_not_windows = partial(pytest.param,
 
 
 def get_example_dir(*names):
-    return join(example_dir, *names)
+    return example_dir.joinpath(*names)
 
 
 def cwd_at(path):
@@ -46,10 +46,10 @@ def cwd_at(path):
 
 @contextmanager
 def set_cwd(path, absolute_path=False):
-    repo_root = os.path.dirname(test_dir)
+    repo_root = test_dir.parent
 
-    oldcwd = os.getcwd()
-    os.chdir(os.path.join(repo_root, path))
+    oldcwd = Path.cwd()
+    os.chdir(repo_root.joinpath(path))
     try:
         yield
     finally:
diff --git a/test/test_api/test_api.py b/test/test_api/test_api.py
index 9f54dbce..107bd52b 100644
--- a/test/test_api/test_api.py
+++ b/test/test_api/test_api.py
@@ -22,7 +22,7 @@ def test_preload_modules():
         # Filter the typeshed parser cache.
         typeshed_cache_count = sum(
             1 for path in grammar_cache
-            if path is not None and path.startswith(typeshed.TYPESHED_PATH)
+            if path is not None and str(path).startswith(str(typeshed.TYPESHED_PATH))
         )
         # +1 for None module (currently used)
         assert len(grammar_cache) - typeshed_cache_count == len(modules) + 1
@@ -210,11 +210,11 @@ def test_goto_follow_imports(Script):
     import inspect
     inspect.isfunction""")
     definition, = Script(code).goto(column=0, follow_imports=True)
-    assert 'inspect.py' in definition.module_path
+    assert definition.module_path.name == 'inspect.py'
     assert (definition.line, definition.column) == (1, 0)
 
     definition, = Script(code).goto(follow_imports=True)
-    assert 'inspect.py' in definition.module_path
+    assert definition.module_path.name == 'inspect.py'
     assert (definition.line, definition.column) > (1, 0)
 
     code = '''def param(p): pass\nparam(1)'''
@@ -245,11 +245,11 @@ def test_goto_module(Script):
         assert module.module_path == expected
 
     base_path = get_example_dir('simple_import')
-    path = os.path.join(base_path, '__init__.py')
+    path = base_path.joinpath('__init__.py')
 
-    check(1, os.path.join(base_path, 'module.py'))
-    check(1, os.path.join(base_path, 'module.py'), follow_imports=True)
-    check(5, os.path.join(base_path, 'module2.py'))
+    check(1, base_path.joinpath('module.py'))
+    check(1, base_path.joinpath('module.py'), follow_imports=True)
+    check(5, base_path.joinpath('module2.py'))
 
 
 def test_goto_definition_cursor(Script):
diff --git a/test/test_api/test_classes.py b/test/test_api/test_classes.py
index 21f9875a..27b227c1 100644
--- a/test/test_api/test_classes.py
+++ b/test/test_api/test_classes.py
@@ -3,7 +3,6 @@
 
 from textwrap import dedent
 from inspect import cleandoc
-import os
 
 import pytest
 
@@ -534,8 +533,8 @@ def test_execute(Script, code, description):
         ('from pkg import Foo; Foo().bar', 'bar', 'module.py'),
     ])
 def test_inheritance_module_path(Script, goto, code, name, file_name):
-    base_path = os.path.join(get_example_dir('inheritance'), 'pkg')
-    whatever_path = os.path.join(base_path, 'NOT_EXISTING.py')
+    base_path = get_example_dir('inheritance', 'pkg')
+    whatever_path = base_path.joinpath('NOT_EXISTING.py')
 
     script = Script(code, path=whatever_path)
     if goto is None:
@@ -544,7 +543,7 @@ def test_inheritance_module_path(Script, goto, code, name, file_name):
         func, = script.goto(follow_imports=goto)
     assert func.type == 'function'
     assert func.name == name
-    assert func.module_path == os.path.join(base_path, file_name)
+    assert func.module_path == base_path.joinpath(file_name)
 
 
 def test_definition_goto_follow_imports(Script):
diff --git a/test/test_api/test_completion.py b/test/test_api/test_completion.py
index 5e11b8c4..7805faba 100644
--- a/test/test_api/test_completion.py
+++ b/test/test_api/test_completion.py
@@ -221,8 +221,8 @@ current_dirname = os.path.basename(dirname(dirname(dirname(__file__))))
         ('example.py', 'rb"' + join('..', current_dirname, 'tes'), None, ['t' + s]),
 
         # Absolute paths
-        (None, '"' + join(root_dir, 'test', 'test_ca'), None, ['che.py"']),
-        (None, '"%s"' % join(root_dir, 'test', 'test_ca'), len(root_dir) + 14, ['che.py']),
+        (None, f'"{root_dir.joinpath("test", "test_ca")}', None, ['che.py"']),
+        (None, f'"{root_dir.joinpath("test", "test_ca")}"', len(str(root_dir)) + 14, ['che.py']),
 
         # Longer quotes
         ('example.py', 'r"""test', None, [s]),
diff --git a/test/test_api/test_keyword.py b/test/test_api/test_keyword.py
index 37e33a88..efafdfa3 100644
--- a/test/test_api/test_keyword.py
+++ b/test/test_api/test_keyword.py
@@ -41,7 +41,7 @@ def test_keyword_attributes(Script):
     assert def_.line is def_.column is None
     assert def_.in_builtin_module() is True
     assert def_.module_name == 'builtins'
-    assert 'typeshed' in def_.module_path
+    assert 'typeshed' in def_.module_path.parts
     assert def_.type == 'keyword'
 
 
diff --git a/test/test_api/test_project.py b/test/test_api/test_project.py
index 2eac0ff1..c9bbe008 100644
--- a/test/test_api/test_project.py
+++ b/test/test_api/test_project.py
@@ -1,4 +1,5 @@
 import os
+from pathlib import Path
 
 import pytest
 
@@ -21,13 +22,12 @@ def test_django_default_project(Script):
 
 def test_django_default_project_of_file(Script):
     project = get_default_project(__file__)
-    d = os.path.dirname
-    assert project._path == d(d(d(__file__)))
+    assert project._path == Path(__file__).parent.parent.parent
 
 
 def test_interpreter_project_path():
     # Run from anywhere it should be the cwd.
-    dir = os.path.join(root_dir, 'test')
+    dir = Path(root_dir).joinpath('test')
     with set_cwd(dir):
         project = Interpreter('', [locals()])._inference_state.project
         assert project._path == dir
diff --git a/test/test_api/test_refactoring.py b/test/test_api/test_refactoring.py
index 24a9d27a..c229c129 100644
--- a/test/test_api/test_refactoring.py
+++ b/test/test_api/test_refactoring.py
@@ -1,5 +1,6 @@
 import os
 from textwrap import dedent
+from pathlib import Path
 
 import pytest
 
@@ -10,22 +11,22 @@ import jedi
 def dir_with_content(tmpdir):
     with open(os.path.join(tmpdir.strpath, 'modx.py'), 'w', newline='') as f:
         f.write('import modx\nfoo\n')  # self reference
-    return tmpdir.strpath
+    return Path(tmpdir.strpath)
 
 
 def test_rename_mod(Script, dir_with_content):
     script = Script(
         'import modx; modx\n',
-        path=os.path.join(dir_with_content, 'some_script.py'),
+        path=dir_with_content.joinpath('some_script.py'),
         project=jedi.Project(dir_with_content),
     )
     refactoring = script.rename(line=1, new_name='modr')
     refactoring.apply()
 
-    p1 = os.path.join(dir_with_content, 'modx.py')
-    p2 = os.path.join(dir_with_content, 'modr.py')
+    p1 = dir_with_content.joinpath('modx.py')
+    p2 = dir_with_content.joinpath('modr.py')
     expected_code = 'import modr\nfoo\n'
-    assert not os.path.exists(p1)
+    assert not p1.exists()
     with open(p2, newline='') as f:
         assert f.read() == expected_code
 
diff --git a/test/test_inference/test_buildout_detection.py b/test/test_inference/test_buildout_detection.py
index 6d646ca7..f15e9a78 100644
--- a/test/test_inference/test_buildout_detection.py
+++ b/test/test_inference/test_buildout_detection.py
@@ -1,5 +1,6 @@
 import os
 from textwrap import dedent
+from pathlib import Path
 
 from jedi.inference.sys_path import _get_parent_dir_with_file, \
     _get_buildout_script_paths, check_sys_path_modifications
@@ -13,18 +14,18 @@ def check_module_test(Script, code):
 
 
 def test_parent_dir_with_file(Script):
-    path = get_example_dir('buildout_project', 'src', 'proj_name')
+    path = Path(get_example_dir('buildout_project', 'src', 'proj_name'))
     parent = _get_parent_dir_with_file(path, 'buildout.cfg')
     assert parent is not None
-    assert parent.endswith(os.path.join('test', 'examples', 'buildout_project'))
+    assert str(parent).endswith(os.path.join('test', 'examples', 'buildout_project'))
 
 
 def test_buildout_detection(Script):
-    path = get_example_dir('buildout_project', 'src', 'proj_name')
-    scripts = list(_get_buildout_script_paths(os.path.join(path, 'module_name.py')))
-    assert len(scripts) == 1
+    path = Path(get_example_dir('buildout_project', 'src', 'proj_name'))
+    paths = list(_get_buildout_script_paths(path.joinpath('module_name.py')))
+    assert len(paths) == 1
     appdir_path = os.path.normpath(os.path.join(path, '../../bin/app'))
-    assert scripts[0] == appdir_path
+    assert str(paths[0]) == appdir_path
 
 
 def test_append_on_non_sys_path(Script):
@@ -79,4 +80,4 @@ def test_path_from_sys_path_assignment(Script):
 
     paths = check_module_test(Script, code)
     assert 1 not in paths
-    assert '/home/test/.buildout/eggs/important_package.egg' in paths
+    assert '/home/test/.buildout/eggs/important_package.egg' in map(str, paths)
diff --git a/test/test_inference/test_gradual/test_stubs.py b/test/test_inference/test_gradual/test_stubs.py
index 71a881d9..b3a042c7 100644
--- a/test/test_inference/test_gradual/test_stubs.py
+++ b/test/test_inference/test_gradual/test_stubs.py
@@ -87,4 +87,4 @@ def test_infer_and_goto(Script, code, full_name, has_stub, has_python, way,
             assert has_python == (not d.is_stub())
         assert d.full_name == full_name
 
-        assert d.is_stub() == d.module_path.endswith('.pyi')
+        assert d.is_stub() == (d.module_path.suffix == '.pyi')
diff --git a/test/test_inference/test_gradual/test_typeshed.py b/test/test_inference/test_gradual/test_typeshed.py
index 890de9b8..ca48db11 100644
--- a/test/test_inference/test_gradual/test_typeshed.py
+++ b/test/test_inference/test_gradual/test_typeshed.py
@@ -14,7 +14,7 @@ TYPESHED_PYTHON3 = os.path.join(typeshed.TYPESHED_PATH, 'stdlib', '3')
 def test_get_typeshed_directories():
     def get_dirs(version_info):
         return {
-            p.path.replace(typeshed.TYPESHED_PATH, '').lstrip(os.path.sep)
+            p.path.replace(str(typeshed.TYPESHED_PATH), '').lstrip(os.path.sep)
             for p in typeshed._get_typeshed_directories(version_info)
         }
 
@@ -52,7 +52,7 @@ def test_keywords_variable(Script):
         assert seq.name == 'Sequence'
         # This points towards the typeshed implementation
         stub_seq, = seq.goto(only_stubs=True)
-        assert typeshed.TYPESHED_PATH in stub_seq.module_path
+        assert str(stub_seq.module_path).startswith(str(typeshed.TYPESHED_PATH))
 
 
 def test_class(Script):
@@ -91,8 +91,12 @@ def test_sys_exc_info(Script):
     none, def_ = Script(code + '[1]').infer()
     # It's an optional.
     assert def_.name == 'BaseException'
+    assert def_.module_path == typeshed.TYPESHED_PATH.joinpath(
+        'stdlib', '2and3', 'builtins.pyi'
+    )
     assert def_.type == 'instance'
     assert none.name == 'NoneType'
+    assert none.module_path is None
 
     none, def_ = Script(code + '[0]').infer()
     assert def_.name == 'BaseException'
@@ -111,7 +115,7 @@ def test_sys_hexversion(Script):
     script = Script('import sys; sys.hexversion')
     def_, = script.complete()
     assert isinstance(def_._name, StubName), def_._name
-    assert typeshed.TYPESHED_PATH in def_.module_path
+    assert str(def_.module_path).startswith(str(typeshed.TYPESHED_PATH))
     def_, = script.infer()
     assert def_.name == 'int'
 
@@ -138,14 +142,14 @@ def test_type_var(Script):
 def test_math_is_stub(Script, code, full_name):
     s = Script(code)
     cos, = s.infer()
-    wanted = os.path.join('typeshed', 'stdlib', '2and3', 'math.pyi')
-    assert cos.module_path.endswith(wanted)
+    wanted = ('typeshed', 'stdlib', '2and3', 'math.pyi')
+    assert cos.module_path.parts[-4:] == wanted
     assert cos.is_stub() is True
     assert cos.goto(only_stubs=True) == [cos]
     assert cos.full_name == full_name
 
     cos, = s.goto()
-    assert cos.module_path.endswith(wanted)
+    assert cos.module_path.parts[-4:] == wanted
     assert cos.goto(only_stubs=True) == [cos]
     assert cos.is_stub() is True
     assert cos.full_name == full_name
diff --git a/test/test_inference/test_imports.py b/test/test_inference/test_imports.py
index 48140d1d..6cc7b051 100644
--- a/test/test_inference/test_imports.py
+++ b/test/test_inference/test_imports.py
@@ -4,6 +4,7 @@ Tests".
 """
 
 import os
+from pathlib import Path
 
 import pytest
 
@@ -38,11 +39,11 @@ def test_find_module_not_package():
     assert is_package is False
 
 
-pkg_zip_path = get_example_dir('zipped_imports', 'pkg.zip')
+pkg_zip_path = Path(get_example_dir('zipped_imports', 'pkg.zip'))
 
 
 def test_find_module_package_zipped(Script, inference_state, environment):
-    sys_path = environment.get_sys_path() + [pkg_zip_path]
+    sys_path = environment.get_sys_path() + [str(pkg_zip_path)]
 
     project = Project('.', sys_path=sys_path)
     script = Script('import pkg; pkg.mod', project=project)
@@ -86,14 +87,14 @@ def test_find_module_package_zipped(Script, inference_state, environment):
 )
 def test_correct_zip_package_behavior(Script, inference_state, environment, code,
                                       file, package, path):
-    sys_path = environment.get_sys_path() + [pkg_zip_path]
+    sys_path = environment.get_sys_path() + [str(pkg_zip_path)]
     pkg, = Script(code, project=Project('.', sys_path=sys_path)).infer()
     value, = pkg._name.infer()
-    assert value.py__file__() == os.path.join(pkg_zip_path, 'pkg', file)
+    assert value.py__file__() == pkg_zip_path.joinpath('pkg', file)
     assert '.'.join(value.py__package__()) == package
     assert value.is_package() is (path is not None)
     if path is not None:
-        assert value.py__path__() == [os.path.join(pkg_zip_path, path)]
+        assert value.py__path__() == [str(pkg_zip_path.joinpath(path))]
 
 
 def test_find_module_not_package_zipped(Script, inference_state, environment):
@@ -103,7 +104,7 @@ def test_find_module_not_package_zipped(Script, inference_state, environment):
     assert len(script.complete()) == 1
 
     file_io, is_package = inference_state.compiled_subprocess.get_module_info(
-        sys_path=sys_path,
+        sys_path=map(str, sys_path),
         string='not_pkg',
         full_name='not_pkg'
     )
@@ -435,8 +436,8 @@ def test_pre_defined_imports_module(Script, environment, name):
     module = Script('', path=path)._get_module_context()
     assert module.string_names == (name,)
 
-    assert module.inference_state.builtins_module.py__file__() != path
-    assert module.inference_state.typing_module.py__file__() != path
+    assert str(module.inference_state.builtins_module.py__file__()) != path
+    assert str(module.inference_state.typing_module.py__file__()) != path
 
 
 @pytest.mark.parametrize('name', ('builtins', 'typing'))
@@ -449,8 +450,8 @@ def test_import_needed_modules_by_jedi(Script, environment, tmpdir, name):
         project=Project('.', sys_path=[tmpdir.strpath] + environment.get_sys_path()),
     )
     module, = script.infer()
-    assert module._inference_state.builtins_module.py__file__() != module_path
-    assert module._inference_state.typing_module.py__file__() != module_path
+    assert str(module._inference_state.builtins_module.py__file__()) != module_path
+    assert str(module._inference_state.typing_module.py__file__()) != module_path
 
 
 def test_import_with_semicolon(Script):
diff --git a/test/test_inference/test_sys_path.py b/test/test_inference/test_sys_path.py
index 300d7935..e0c6d74e 100644
--- a/test/test_inference/test_sys_path.py
+++ b/test/test_inference/test_sys_path.py
@@ -2,6 +2,7 @@ import os
 from glob import glob
 import sys
 import shutil
+from pathlib import Path, PurePath
 
 import pytest
 
@@ -17,9 +18,9 @@ def test_paths_from_assignment(Script):
         return set(sys_path._paths_from_assignment(script._get_module_context(), expr_stmt))
 
     # Normalize paths for Windows.
-    path_a = os.path.abspath('/foo/a')
-    path_b = os.path.abspath('/foo/b')
-    path_c = os.path.abspath('/foo/c')
+    path_a = PurePath('/foo/a')
+    path_b = PurePath('/foo/b')
+    path_c = PurePath('/foo/c')
 
     assert paths('sys.path[0:0] = ["a"]') == {path_a}
     assert paths('sys.path = ["b", 1, x + 3, y, "c"]') == {path_b, path_c}
@@ -105,5 +106,5 @@ def test_transform_path_to_dotted(sys_path_, module_path, expected, is_package):
     # transform_path_to_dotted expects normalized absolute paths.
     sys_path_ = [os.path.abspath(path) for path in sys_path_]
     module_path = os.path.abspath(module_path)
-    assert sys_path.transform_path_to_dotted(sys_path_, module_path) \
+    assert sys_path.transform_path_to_dotted(sys_path_, Path(module_path)) \
         == (expected, is_package)