diff --git a/tests/test_state.py b/tests/test_state.py
new file mode 100644
index 0000000..3112399
--- /dev/null
+++ b/tests/test_state.py
@@ -0,0 +1,171 @@
+from unittest.mock import MagicMock, Mock, call
+
+from hypothesis import given, settings
+from hypothesis import strategies as st
+
+from atpbar.machine import (
+    Active,
+    Callback,
+    Disabled,
+    Initial,
+    Lock,
+    ProgressReporter,
+    Registered,
+    State,
+    Yielded,
+)
+
+
+class StatefulTest:
+    def __init__(self) -> None:
+        self.callback = MagicMock(spec=Callback)
+        self.reporter = Mock(spec=ProgressReporter)
+        self.callback.reporter = self.reporter
+        self.state: State = Initial(callback=self.callback)
+
+    def prepare_reporter(self) -> None:
+        prev = self.state
+        self.callback.reset_mock()
+        self.state = prev.prepare_reporter()
+        match prev:
+            case Initial():
+                assert isinstance(self.state, Active)
+                assert self.callback.mock_calls == [call.on_active()]
+            case _:
+                assert self.state is prev
+                assert self.callback.mock_calls == []
+
+    def register_reporter(self) -> None:
+        prev = self.state
+        self.callback.reset_mock()
+        reporter = Mock(spec=ProgressReporter)
+        self.state = prev.register_reporter(reporter)
+        assert isinstance(self.state, Registered)
+        assert self.callback.mock_calls == [call.on_registered(reporter)]
+
+    def disable(self) -> None:
+        prev = self.state
+        self.callback.reset_mock()
+        self.state = prev.disable()
+        assert isinstance(self.state, Disabled)
+        assert self.callback.mock_calls == [call.on_disabled()]
+
+    def fetch_reporter(self) -> None:
+        prev = self.state
+        self.callback.reset_mock()
+
+        lock = Lock()
+
+        with prev.fetch_reporter(lock=lock) as reporter:
+            match prev:
+                case Active():
+                    assert self.callback.mock_calls == [
+                        call.fetch_reporter_in_active(lock=lock),
+                        call.fetch_reporter_in_active(lock=lock).__enter__(),
+                    ]
+                    assert (
+                        reporter
+                        is self.callback.fetch_reporter_in_active.return_value.__enter__.return_value
+                    )
+                case Yielded():
+                    assert self.callback.mock_calls == [
+                        call.fetch_reporter_in_yielded(lock=lock),
+                        call.fetch_reporter_in_yielded(lock=lock).__enter__(),
+                    ]
+                    assert (
+                        reporter
+                        is self.callback.fetch_reporter_in_yielded.return_value.__enter__.return_value
+                    )
+                case Registered():
+                    assert self.callback.mock_calls == [
+                        call.fetch_reporter_in_registered(lock=lock),
+                        call.fetch_reporter_in_registered(lock=lock).__enter__(),
+                    ]
+                    assert (
+                        reporter
+                        is self.callback.fetch_reporter_in_registered.return_value.__enter__.return_value
+                    )
+                case Disabled():
+                    assert self.callback.mock_calls == [
+                        call.fetch_reporter_in_disabled(lock=lock),
+                        call.fetch_reporter_in_disabled(lock=lock).__enter__(),
+                    ]
+                    assert (
+                        reporter
+                        is self.callback.fetch_reporter_in_disabled.return_value.__enter__.return_value
+                    )
+                case _:
+                    assert self.callback.mock_calls == []
+                    assert reporter is self.reporter
+
+    def on_yielded(self) -> None:
+        prev = self.state
+        self.callback.reset_mock()
+        self.state = prev.on_yielded()
+        match prev:
+            case Active():
+                assert isinstance(self.state, Yielded)
+            case _:
+                assert self.state is prev
+        assert self.callback.mock_calls == []
+
+    def on_resumed(self) -> None:
+        prev = self.state
+        self.callback.reset_mock()
+        self.state = prev.on_resumed()
+        match prev:
+            case Yielded():
+                assert isinstance(self.state, Active)
+                assert self.state is prev._active
+            case _:
+                assert self.state is prev
+        assert self.callback.mock_calls == []
+
+    def flush(self) -> None:
+        prev = self.state
+        self.callback.reset_mock()
+        self.state = prev.flush()
+        match prev:
+            case Initial():
+                assert isinstance(self.state, Active)
+                assert self.callback.mock_calls == [call.on_active()]
+            case Active():
+                assert self.state is prev
+                assert self.callback.mock_calls == [call.flush_in_active()]
+            case _:
+                assert self.state is prev
+                assert self.callback.mock_calls == []
+
+    def shutdown(self) -> None:
+        prev = self.state
+        self.callback.reset_mock()
+        self.state = prev.shutdown()
+        match prev:
+            case Active():
+                assert isinstance(self.state, Initial)
+                assert self.callback.mock_calls == [call.shutdown_in_active()]
+            case _:
+                assert self.state is prev
+                assert self.callback.mock_calls == []
+
+
+@settings(max_examples=500)
+@given(data=st.data())
+def test_state(data: st.DataObject) -> None:
+    test = StatefulTest()
+
+    METHODS = [
+        test.prepare_reporter,
+        test.register_reporter,
+        test.disable,
+        test.fetch_reporter,
+        test.on_yielded,
+        test.on_resumed,
+        test.flush,
+        test.shutdown,
+    ]
+
+    methods = data.draw(st.lists(st.sampled_from(METHODS)))
+
+    for method in methods:
+        method()