diff --git a/python-stdlib/unittest-discover/manifest.py b/python-stdlib/unittest-discover/manifest.py
new file mode 100644
index 00000000..28874c7e
--- /dev/null
+++ b/python-stdlib/unittest-discover/manifest.py
@@ -0,0 +1,7 @@
+metadata(version="0.1.0")
+
+require("argparse")
+require("fnmatch")
+require("unittest")
+
+module("unittest_discover.py")
diff --git a/python-stdlib/unittest-discover/tests/isolated.py b/python-stdlib/unittest-discover/tests/isolated.py
new file mode 100644
index 00000000..21b905c1
--- /dev/null
+++ b/python-stdlib/unittest-discover/tests/isolated.py
@@ -0,0 +1,4 @@
+# Module that is used in both test_isolated_1.py and test_isolated_2.py.
+# The module should be clean reloaded for each.
+
+state = None
diff --git a/python-stdlib/unittest-discover/tests/test_isolated_1.py b/python-stdlib/unittest-discover/tests/test_isolated_1.py
new file mode 100644
index 00000000..a2bd83b1
--- /dev/null
+++ b/python-stdlib/unittest-discover/tests/test_isolated_1.py
@@ -0,0 +1,8 @@
+import unittest
+import isolated
+
+
+class TestUnittestIsolated1(unittest.TestCase):
+    def test_NotChangedByOtherTest(self):
+        self.assertIsNone(isolated.state)
+        isolated.state = True
diff --git a/python-stdlib/unittest-discover/tests/test_isolated_2.py b/python-stdlib/unittest-discover/tests/test_isolated_2.py
new file mode 100644
index 00000000..1beb9961
--- /dev/null
+++ b/python-stdlib/unittest-discover/tests/test_isolated_2.py
@@ -0,0 +1,8 @@
+import unittest
+import isolated
+
+
+class TestUnittestIsolated2(unittest.TestCase):
+    def test_NotChangedByOtherTest(self):
+        self.assertIsNone(isolated.state)
+        isolated.state = True
diff --git a/python-stdlib/unittest-discover/unittest_discover.py b/python-stdlib/unittest-discover/unittest_discover.py
new file mode 100644
index 00000000..b57ccf39
--- /dev/null
+++ b/python-stdlib/unittest-discover/unittest_discover.py
@@ -0,0 +1,140 @@
+# Extension for "unittest" that adds the ability to run via "micropython -m unittest".
+
+import argparse
+import os
+import sys
+from fnmatch import fnmatch
+from micropython import const
+
+from unittest import TestRunner, TestResult, TestSuite
+
+
+# Run a single test in a clean environment.
+def _run_test_module(runner: TestRunner, module_name: str, *extra_paths: list[str]):
+    module_snapshot = {k: v for k, v in sys.modules.items()}
+    path_snapshot = sys.path[:]
+    try:
+        for path in reversed(extra_paths):
+            if path:
+                sys.path.insert(0, path)
+
+        module = __import__(module_name)
+        suite = TestSuite(module_name)
+        suite._load_module(module)
+        return runner.run(suite)
+    finally:
+        sys.path[:] = path_snapshot
+        sys.modules.clear()
+        sys.modules.update(module_snapshot)
+
+
+_DIR_TYPE = const(0x4000)
+
+
+def _run_all_in_dir(runner: TestRunner, path: str, pattern: str, top: str):
+    result = TestResult()
+    for fname, ftype, *_ in os.ilistdir(path):
+        if fname in ("..", "."):
+            continue
+        if ftype == _DIR_TYPE:
+            result += _run_all_in_dir(
+                runner=runner,
+                path="/".join((path, fname)),
+                pattern=pattern,
+                top=top,
+            )
+        if fnmatch(fname, pattern):
+            module_name = fname.rsplit(".", 1)[0]
+            result += _run_test_module(runner, module_name, path, top)
+    return result
+
+
+# Implements discovery inspired by https://docs.python.org/3/library/unittest.html#test-discovery
+def _discover(runner: TestRunner):
+    parser = argparse.ArgumentParser()
+    # parser.add_argument(
+    #     "-v",
+    #     "--verbose",
+    #     action="store_true",
+    #     help="Verbose output",
+    # )
+    parser.add_argument(
+        "-s",
+        "--start-directory",
+        dest="start",
+        default=".",
+        help="Directory to start discovery",
+    )
+    parser.add_argument(
+        "-p",
+        "--pattern ",
+        dest="pattern",
+        default="test*.py",
+        help="Pattern to match test files",
+    )
+    parser.add_argument(
+        "-t",
+        "--top-level-directory",
+        dest="top",
+        help="Top level directory of project (defaults to start directory)",
+    )
+    args = parser.parse_args(args=sys.argv[2:])
+
+    path = args.start
+    top = args.top or path
+
+    return _run_all_in_dir(
+        runner=runner,
+        path=path,
+        pattern=args.pattern,
+        top=top,
+    )
+
+
+# TODO: Use os.path for path handling.
+PATH_SEP = getattr(os, "sep", "/")
+
+
+# foo/bar/x.y.z --> foo/bar, x.y
+def _dirname_filename_no_ext(path):
+    # Workaround: The Windows port currently reports "/" for os.sep
+    # (and MicroPython doesn't have os.altsep). So for now just
+    # always work with os.sep (i.e. "/").
+    path = path.replace("\\", PATH_SEP)
+
+    split = path.rsplit(PATH_SEP, 1)
+    if len(split) == 1:
+        dirname, filename = "", split[0]
+    else:
+        dirname, filename = split
+    return dirname, filename.rsplit(".", 1)[0]
+
+
+# This is called from unittest when __name__ == "__main__".
+def discover_main():
+    failures = 0
+    runner = TestRunner()
+
+    if len(sys.argv) == 1 or (
+        len(sys.argv) >= 2
+        and _dirname_filename_no_ext(sys.argv[0])[1] == "unittest"
+        and sys.argv[1] == "discover"
+    ):
+        # No args, or `python -m unittest discover ...`.
+        result = _discover(runner)
+        failures += result.failuresNum or result.errorsNum
+    else:
+        for test_spec in sys.argv[1:]:
+            try:
+                os.stat(test_spec)
+                # File exists, strip extension and import with its parent directory in sys.path.
+                dirname, module_name = _dirname_filename_no_ext(test_spec)
+                result = _run_test_module(runner, module_name, dirname)
+            except OSError:
+                # Not a file, treat as named module to import.
+                result = _run_test_module(runner, test_spec)
+
+            failures += result.failuresNum or result.errorsNum
+
+    # Terminate with non zero return code in case of failures.
+    sys.exit(failures)
diff --git a/python-stdlib/unittest/manifest.py b/python-stdlib/unittest/manifest.py
new file mode 100644
index 00000000..34c80075
--- /dev/null
+++ b/python-stdlib/unittest/manifest.py
@@ -0,0 +1,3 @@
+metadata(version="0.10.0")
+
+module("unittest.py")
diff --git a/unix-ffi/unittest/test_unittest.py b/python-stdlib/unittest/tests/test_assertions.py
similarity index 84%
rename from unix-ffi/unittest/test_unittest.py
rename to python-stdlib/unittest/tests/test_assertions.py
index 8e108995..089a528a 100644
--- a/unix-ffi/unittest/test_unittest.py
+++ b/python-stdlib/unittest/tests/test_assertions.py
@@ -1,5 +1,4 @@
 import unittest
-from test_unittest_isolated import global_context
 
 
 class TestUnittestAssertions(unittest.TestCase):
@@ -143,11 +142,6 @@ class TestUnittestAssertions(unittest.TestCase):
         else:
             self.fail("Unexpected success was not detected")
 
-    def test_NotChangedByOtherTest(self):
-        global global_context
-        assert global_context is None
-        global_context = True
-
     def test_subtest_even(self):
         """
         Test that numbers between 0 and 5 are all even.
@@ -157,24 +151,5 @@ class TestUnittestAssertions(unittest.TestCase):
                 self.assertEqual(i % 2, 0)
 
 
-class TestUnittestSetup(unittest.TestCase):
-    class_setup_var = 0
-
-    def setUpClass(self):
-        TestUnittestSetup.class_setup_var += 1
-
-    def tearDownClass(self):
-        # Not sure how to actually test this, but we can check (in the test case below)
-        # that it hasn't been run already at least.
-        TestUnittestSetup.class_setup_var = -1
-
-    def testSetUpTearDownClass_1(self):
-        assert TestUnittestSetup.class_setup_var == 1, TestUnittestSetup.class_setup_var
-
-    def testSetUpTearDownClass_2(self):
-        # Test this twice, as if setUpClass() gets run like setUp() it would be run twice
-        assert TestUnittestSetup.class_setup_var == 1, TestUnittestSetup.class_setup_var
-
-
 if __name__ == "__main__":
     unittest.main()
diff --git a/python-stdlib/unittest/tests/test_basics.py b/python-stdlib/unittest/tests/test_basics.py
new file mode 100644
index 00000000..70f0dd61
--- /dev/null
+++ b/python-stdlib/unittest/tests/test_basics.py
@@ -0,0 +1,29 @@
+import unittest
+
+
+class TestWithRunTest(unittest.TestCase):
+    run = False
+
+    def runTest(self):
+        TestWithRunTest.run = True
+
+    def testRunTest(self):
+        self.fail()
+
+    @staticmethod
+    def tearDownClass():
+        if not TestWithRunTest.run:
+            raise ValueError()
+
+
+def test_func():
+    pass
+
+
+@unittest.expectedFailure
+def test_foo():
+    raise ValueError()
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/python-stdlib/unittest/tests/test_setup.py b/python-stdlib/unittest/tests/test_setup.py
new file mode 100644
index 00000000..43fdcece
--- /dev/null
+++ b/python-stdlib/unittest/tests/test_setup.py
@@ -0,0 +1,28 @@
+import unittest
+
+
+class TestUnittestSetup(unittest.TestCase):
+    class_setup_var = 0
+
+    @classmethod
+    def setUpClass(cls):
+        assert cls is TestUnittestSetup
+        TestUnittestSetup.class_setup_var += 1
+
+    @classmethod
+    def tearDownClass(cls):
+        assert cls is TestUnittestSetup
+        # Not sure how to actually test this, but we can check (in the test case below)
+        # that it hasn't been run already at least.
+        TestUnittestSetup.class_setup_var = -1
+
+    def testSetUpTearDownClass_1(self):
+        assert TestUnittestSetup.class_setup_var == 1, TestUnittestSetup.class_setup_var
+
+    def testSetUpTearDownClass_2(self):
+        # Test this twice, as if setUpClass() gets run like setUp() it would be run twice
+        assert TestUnittestSetup.class_setup_var == 1, TestUnittestSetup.class_setup_var
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/unix-ffi/unittest/unittest.py b/python-stdlib/unittest/unittest.py
similarity index 77%
rename from unix-ffi/unittest/unittest.py
rename to python-stdlib/unittest/unittest.py
index b6168698..35ed14ac 100644
--- a/unix-ffi/unittest/unittest.py
+++ b/python-stdlib/unittest/unittest.py
@@ -1,22 +1,13 @@
+import io
+import os
 import sys
-import uos
 
 try:
-    import io
     import traceback
 except ImportError:
-    import uio as io
-
     traceback = None
 
 
-def _snapshot_modules():
-    return {k: v for k, v in sys.modules.items()}
-
-
-__modules__ = _snapshot_modules()
-
-
 class SkipTest(Exception):
     pass
 
@@ -61,7 +52,7 @@ class SubtestContext:
                 detail = ", ".join(f"{k}={v}" for k, v in self.params.items())
                 test_details += (f" ({detail})",)
 
-            handle_test_exception(test_details, __test_result__, exc_info, False)
+            _handle_test_exception(test_details, __test_result__, exc_info, False)
         # Suppress the exception as we've captured it above
         return True
 
@@ -258,9 +249,17 @@ class TestSuite:
 
     def run(self, result):
         for c in self._tests:
-            run_suite(c, result, self.name)
+            _run_suite(c, result, self.name)
         return result
 
+    def _load_module(self, mod):
+        for tn in dir(mod):
+            c = getattr(mod, tn)
+            if isinstance(c, object) and isinstance(c, type) and issubclass(c, TestCase):
+                self.addTest(c)
+            elif tn.startswith("test") and callable(c):
+                self.addTest(c)
+
 
 class TestRunner:
     def run(self, suite: TestSuite):
@@ -331,7 +330,7 @@ class TestResult:
         return self
 
 
-def capture_exc(exc, traceback):
+def _capture_exc(exc, traceback):
     buf = io.StringIO()
     if hasattr(sys, "print_exception"):
         sys.print_exception(exc, buf)
@@ -340,12 +339,12 @@ def capture_exc(exc, traceback):
     return buf.getvalue()
 
 
-def handle_test_exception(
+def _handle_test_exception(
     current_test: tuple, test_result: TestResult, exc_info: tuple, verbose=True
 ):
     exc = exc_info[1]
     traceback = exc_info[2]
-    ex_str = capture_exc(exc, traceback)
+    ex_str = _capture_exc(exc, traceback)
     if isinstance(exc, AssertionError):
         test_result.failuresNum += 1
         test_result.failures.append((current_test, ex_str))
@@ -359,7 +358,7 @@ def handle_test_exception(
     test_result._newFailures += 1
 
 
-def run_suite(c, test_result: TestResult, suite_name=""):
+def _run_suite(c, test_result: TestResult, suite_name=""):
     if isinstance(c, TestSuite):
         c.run(test_result)
         return
@@ -388,9 +387,7 @@ def run_suite(c, test_result: TestResult, suite_name=""):
         try:
             test_result._newFailures = 0
             test_result.testsRun += 1
-            test_globals = dict(**globals())
-            test_globals["test_function"] = test_function
-            exec("test_function()", test_globals, test_globals)
+            test_function()
             # No exception occurred, test passed
             if test_result._newFailures:
                 print(" FAIL")
@@ -402,7 +399,7 @@ def run_suite(c, test_result: TestResult, suite_name=""):
             test_result.skippedNum += 1
             test_result.skipped.append((name, c, reason))
         except Exception as ex:
-            handle_test_exception(
+            _handle_test_exception(
                 current_test=(name, c), test_result=test_result, exc_info=sys.exc_info()
             )
             # Uncomment to investigate failure in detail
@@ -417,102 +414,59 @@ def run_suite(c, test_result: TestResult, suite_name=""):
                 pass
 
     set_up_class()
+    try:
+        if hasattr(o, "runTest"):
+            name = str(o)
+            run_one(o.runTest)
+            return
 
-    if hasattr(o, "runTest"):
-        name = str(o)
-        run_one(o.runTest)
-        return
+        for name in dir(o):
+            if name.startswith("test"):
+                m = getattr(o, name)
+                if not callable(m):
+                    continue
+                run_one(m)
 
-    for name in dir(o):
-        if name.startswith("test"):
-            m = getattr(o, name)
-            if not callable(m):
-                continue
-            run_one(m)
-
-    if callable(o):
-        name = o.__name__
-        run_one(o)
-
-    tear_down_class()
+        if callable(o):
+            name = o.__name__
+            run_one(o)
+    finally:
+        tear_down_class()
 
     return exceptions
 
 
-def _test_cases(mod):
-    for tn in dir(mod):
-        c = getattr(mod, tn)
-        if isinstance(c, object) and isinstance(c, type) and issubclass(c, TestCase):
-            yield c
-        elif tn.startswith("test_") and callable(c):
-            yield c
-
-
-def run_module(runner, module, path, top):
-    if not module:
-        raise ValueError("Empty module name")
-
-    # Reset the python environment before running test
-    sys.modules.clear()
-    sys.modules.update(__modules__)
-
-    sys_path_initial = sys.path[:]
-    # Add script dir and top dir to import path
-    sys.path.insert(0, str(path))
-    if top:
-        sys.path.insert(1, top)
-    try:
-        suite = TestSuite(module)
-        m = __import__(module) if isinstance(module, str) else module
-        for c in _test_cases(m):
-            suite.addTest(c)
-        result = runner.run(suite)
-        return result
-
-    finally:
-        sys.path[:] = sys_path_initial
-
-
-def discover(runner: TestRunner):
-    from unittest_discover import discover
-
-    global __modules__
-    __modules__ = _snapshot_modules()
-    return discover(runner=runner)
-
-
+# This supports either:
+#
+# >>> import mytest
+# >>> unitttest.main(mytest)
+#
+# >>> unittest.main("mytest")
+#
+# Or, a script that ends with:
+# if __name__ == "__main__":
+#     unittest.main()
+# e.g. run via `mpremote run mytest.py`
 def main(module="__main__", testRunner=None):
-    if testRunner:
-        if isinstance(testRunner, type):
-            runner = testRunner()
-        else:
-            runner = testRunner
-    else:
-        runner = TestRunner()
+    if testRunner is None:
+        testRunner = TestRunner()
+    elif isinstance(testRunner, type):
+        testRunner = testRunner()
 
-    if len(sys.argv) <= 1:
-        result = discover(runner)
-    elif sys.argv[0].split(".")[0] == "unittest" and sys.argv[1] == "discover":
-        result = discover(runner)
-    else:
-        for test_spec in sys.argv[1:]:
-            try:
-                uos.stat(test_spec)
-                # test_spec is a local file, run it directly
-                if "/" in test_spec:
-                    path, fname = test_spec.rsplit("/", 1)
-                else:
-                    path, fname = ".", test_spec
-                modname = fname.rsplit(".", 1)[0]
-                result = run_module(runner, modname, path, None)
-
-            except OSError:
-                # Not a file, treat as import name
-                result = run_module(runner, test_spec, ".", None)
-
-    # Terminate with non zero return code in case of failures
-    sys.exit(result.failuresNum or result.errorsNum)
+    if isinstance(module, str):
+        module = __import__(module)
+    suite = TestSuite(module.__name__)
+    suite._load_module(module)
+    return testRunner.run(suite)
 
 
+# Support `micropython -m unittest` (only useful if unitest-discover is
+# installed).
 if __name__ == "__main__":
-    main()
+    try:
+        # If unitest-discover is installed, use the main() provided there.
+        from unittest_discover import discover_main
+
+        discover_main()
+    except ImportError:
+        pass
diff --git a/unix-ffi/unittest/manifest.py b/unix-ffi/unittest/manifest.py
deleted file mode 100644
index 85a5f401..00000000
--- a/unix-ffi/unittest/manifest.py
+++ /dev/null
@@ -1,6 +0,0 @@
-metadata(version="0.9.0")
-
-require("argparse")
-require("fnmatch")
-
-module("unittest.py")
diff --git a/unix-ffi/unittest/test_unittest_isolated.py b/unix-ffi/unittest/test_unittest_isolated.py
deleted file mode 100644
index a828f9a3..00000000
--- a/unix-ffi/unittest/test_unittest_isolated.py
+++ /dev/null
@@ -1,15 +0,0 @@
-import unittest
-
-
-global_context = None
-
-
-class TestUnittestIsolated(unittest.TestCase):
-    def test_NotChangedByOtherTest(self):
-        global global_context
-        assert global_context is None
-        global_context = True
-
-
-if __name__ == "__main__":
-    unittest.main()
diff --git a/unix-ffi/unittest/unittest_discover.py b/unix-ffi/unittest/unittest_discover.py
deleted file mode 100644
index 7c5abd1f..00000000
--- a/unix-ffi/unittest/unittest_discover.py
+++ /dev/null
@@ -1,70 +0,0 @@
-import argparse
-import sys
-import uos
-from fnmatch import fnmatch
-
-from unittest import TestRunner, TestResult, run_module
-
-
-def discover(runner: TestRunner):
-    """
-    Implements discover function inspired by https://docs.python.org/3/library/unittest.html#test-discovery
-    """
-    parser = argparse.ArgumentParser()
-    # parser.add_argument(
-    #     "-v",
-    #     "--verbose",
-    #     action="store_true",
-    #     help="Verbose output",
-    # )
-    parser.add_argument(
-        "-s",
-        "--start-directory",
-        dest="start",
-        default=".",
-        help="Directory to start discovery",
-    )
-    parser.add_argument(
-        "-p",
-        "--pattern ",
-        dest="pattern",
-        default="test*.py",
-        help="Pattern to match test files",
-    )
-    parser.add_argument(
-        "-t",
-        "--top-level-directory",
-        dest="top",
-        help="Top level directory of project (defaults to start directory)",
-    )
-    args = parser.parse_args(args=sys.argv[2:])
-
-    path = args.start
-    top = args.top or path
-
-    return run_all_in_dir(
-        runner=runner,
-        path=path,
-        pattern=args.pattern,
-        top=top,
-    )
-
-
-def run_all_in_dir(runner: TestRunner, path: str, pattern: str, top: str):
-    DIR_TYPE = 0x4000
-
-    result = TestResult()
-    for fname, type, *_ in uos.ilistdir(path):
-        if fname in ("..", "."):
-            continue
-        if type == DIR_TYPE:
-            result += run_all_in_dir(
-                runner=runner,
-                path="/".join((path, fname)),
-                pattern=pattern,
-                top=top,
-            )
-        if fnmatch(fname, pattern):
-            modname = fname[: fname.rfind(".")]
-            result += run_module(runner, modname, path, top)
-    return result