diff --git a/sysaudit/__init__.py b/sysaudit/__init__.py
index ffbf0b9..24af53c 100644
--- a/sysaudit/__init__.py
+++ b/sysaudit/__init__.py
@@ -102,6 +102,10 @@ class Span:
         return self
 
     def end(self, data=None):
+        if not self.started:
+            raise RuntimeError(
+                "Attempting to end span {} before it was started".format(self)
+            )
         if not self.ended:
             self.message("end", data)
             self.ended = True
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/base.py b/tests/base.py
new file mode 100644
index 0000000..b0728be
--- /dev/null
+++ b/tests/base.py
@@ -0,0 +1,45 @@
+import subprocess
+import sys
+import unittest
+
+
+class BaseTest(unittest.TestCase):
+    TEST_FILE_PY = None
+
+    def do_test(self, *args):
+        popen_kwargs = dict(
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+        )
+        if sys.version_info >= (3, 6):
+            popen_kwargs["encoding"] = "utf-8"
+
+        p = subprocess.Popen(
+            [sys.executable, self.TEST_FILE_PY] + list(args), **popen_kwargs
+        )
+        p.wait()
+        sys.stdout.writelines(p.stdout)
+        sys.stderr.writelines(p.stderr)
+        if p.returncode:
+            self.fail("".join(p.stderr))
+
+    def run_python(self, *args):
+        events = []
+
+        popen_kwargs = dict(
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+        )
+        if sys.version_info >= (3, 6):
+            popen_kwargs["encoding"] = "utf-8"
+
+        p = subprocess.Popen(
+            [sys.executable, self.TEST_FILE_PY] + list(args), **popen_kwargs
+        )
+        p.wait()
+        sys.stderr.writelines(p.stderr)
+        return (
+            p.returncode,
+            [line.strip().partition(" ") for line in p.stdout],
+            "".join(p.stderr),
+        )
diff --git a/tests/span-tests.py b/tests/span-tests.py
new file mode 100644
index 0000000..8296af1
--- /dev/null
+++ b/tests/span-tests.py
@@ -0,0 +1,150 @@
+import mock
+import pytest
+
+import sysaudit
+
+
+def assert_span_message(span, call_args, type, data=None):
+    (args,) = call_args
+    (message,) = args
+
+    assert isinstance(message, sysaudit.Span.Message)
+    assert message.span == span
+    assert message.type == type
+    assert message.data == data
+
+
+def assert_start_message(span, call_args, data=None):
+    assert_span_message(span, call_args, "start", data=data)
+
+
+def assert_end_message(span, call_args, data=None):
+    assert_span_message(span, call_args, "end", data=data)
+
+
+def assert_annotate_message(span, call_args, data=None):
+    assert_span_message(span, call_args, "annotate", data=data)
+
+
+def test_properties():
+    # Name only
+    span = sysaudit.Span("span.name")
+    assert span.started is False
+    assert span.ended is False
+    assert span.data is None
+    assert span.name == "span.name"
+    assert span.id == id(span)
+
+    # Name and data
+    span = sysaudit.Span("span.name", data="some-data")
+    assert span.started is False
+    assert span.ended is False
+    assert span.data == "some-data"
+    assert span.name == "span.name"
+    assert span.id == id(span)
+
+
+def test_started_ended():
+    span = sysaudit.Span("span.name")
+
+    span.start()
+    assert span.started is True
+    assert span.ended is False
+
+    span.end()
+    assert span.started is True
+    assert span.ended is True
+
+
+def test_started_ended_contextmanager():
+    span = sysaudit.Span("span.name")
+    with span:
+        assert span.started is True
+        assert span.ended is False
+
+    assert span.started is True
+    assert span.ended is True
+
+
+def test_lifecycle_events():
+    hook = mock.Mock()
+    sysaudit.subscribe("span.name", hook)
+
+    span = sysaudit.Span("span.name")
+    hook.assert_not_called()
+
+    span.start()
+    assert hook.call_count == 1
+    assert_start_message(span, hook.call_args[0])
+
+    # Call a second time
+    span.start()
+    # We did not emit a second start message
+    assert hook.call_count == 1
+
+    span.end()
+    assert hook.call_count == 2
+    assert_end_message(span, hook.call_args[0])
+
+    # Call a second time
+    span.end()
+    # We did not emit a second end message
+    assert hook.call_count == 2
+
+
+def test_lifecycle_events_contextmanager():
+    hook = mock.Mock()
+    sysaudit.subscribe("span.name", hook)
+
+    with sysaudit.Span("span.name") as span:
+        assert hook.call_count == 1
+        assert_start_message(span, hook.call_args[0])
+
+    assert hook.call_count == 2
+    assert_end_message(
+        span, hook.call_args[0], data=dict(exc_tb=None, exc_type=None, exc_val=None)
+    )
+
+
+def test_lifecycle_events_data():
+    hook = mock.Mock()
+    sysaudit.subscribe("span.name", hook)
+
+    span = sysaudit.Span("span.name")
+
+    span.start("start-data")
+    assert hook.call_count == 1
+    assert_start_message(span, hook.call_args[0], data="start-data")
+
+    span.end("end-data")
+    assert hook.call_count == 2
+    assert_end_message(span, hook.call_args[0], data="end-data")
+
+
+def test_end_before_start():
+    span = sysaudit.Span("span.name")
+
+    with pytest.raises(RuntimeError):
+        span.end()
+
+
+def test_custom_message():
+    hook = mock.Mock()
+    sysaudit.subscribe("span.name", hook)
+
+    span = sysaudit.Span("span.name")
+    span.message("custom", "message")
+
+    assert hook.call_count == 1
+    assert_span_message(span, hook.call_args[0], type="custom", data="message")
+
+
+def test_annotate_message():
+    hook = mock.Mock()
+    sysaudit.subscribe("span.name", hook)
+
+    span = sysaudit.Span("span.name")
+    span.annotate("extra-data")
+
+    assert hook.call_count == 1
+    assert_annotate_message(span, hook.call_args[0], data="extra-data")
diff --git a/tests/subscribe-tests.py b/tests/subscribe-tests.py
new file mode 100644
index 0000000..b6ff71c
--- /dev/null
+++ b/tests/subscribe-tests.py
@@ -0,0 +1,45 @@
+import mock
+
+import sysaudit
+
+
+def test_basic():
+    test_hook = mock.Mock()
+    event_hook = mock.Mock()
+
+    sysaudit.subscribe("test", test_hook)
+    sysaudit.subscribe("event", event_hook)
+
+    assert sysaudit._subscriptions == dict(test=[test_hook], event=[event_hook])
+
+    sysaudit.audit("test", 1)
+    sysaudit.audit("test", 2)
+    sysaudit.audit("event", 3)
+    sysaudit.audit("event", 4)
+    sysaudit.audit("event", 5)
+
+    assert test_hook.mock_calls == [
+        mock.call((1,)),
+        mock.call((2,)),
+    ]
+    assert event_hook.mock_calls == [
+        mock.call((3,)),
+        mock.call((4,)),
+        mock.call((5,)),
+    ]
+
+
+def test_multiple_hooks():
+    test_hook_1 = mock.Mock()
+    test_hook_2 = mock.Mock()
+    test_hook_3 = mock.Mock()
+
+    sysaudit.subscribe("test", test_hook_1)
+    sysaudit.subscribe("test", test_hook_2)
+    sysaudit.subscribe("test", test_hook_3)
+
+    sysaudit.audit("test", 1)
+
+    test_hook_1.assert_called_once_with(((1,)))
+    test_hook_2.assert_called_once_with(((1,)))
+    test_hook_3.assert_called_once_with(((1,)))
diff --git a/tests/test_audit.py b/tests/test_audit.py
index 9942e78..a02e0ea 100644
--- a/tests/test_audit.py
+++ b/tests/test_audit.py
@@ -8,54 +8,18 @@ import subprocess
 import sys
 import unittest
 
+from .base import BaseTest
 
-AUDIT_TESTS_PY = os.path.abspath(
-    os.path.join(os.path.dirname(__file__), "audit-tests.py")
-)
 
 skip_old_py = unittest.skipIf(
     sys.version_info < (3, 8), "Skipping tests testing built-in events"
 )
 
 
-class AuditTest(unittest.TestCase):
-    def do_test(self, *args):
-        popen_kwargs = dict(
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
-        )
-        if sys.version_info >= (3, 6):
-            popen_kwargs["encoding"] = "utf-8"
-
-        p = subprocess.Popen(
-            [sys.executable, AUDIT_TESTS_PY] + list(args), **popen_kwargs
-        )
-        p.wait()
-        sys.stdout.writelines(p.stdout)
-        sys.stderr.writelines(p.stderr)
-        if p.returncode:
-            self.fail("".join(p.stderr))
-
-    def run_python(self, *args):
-        events = []
-
-        popen_kwargs = dict(
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
-        )
-        if sys.version_info >= (3, 6):
-            popen_kwargs["encoding"] = "utf-8"
-
-        p = subprocess.Popen(
-            [sys.executable, AUDIT_TESTS_PY] + list(args), **popen_kwargs
-        )
-        p.wait()
-        sys.stderr.writelines(p.stderr)
-        return (
-            p.returncode,
-            [line.strip().partition(" ") for line in p.stdout],
-            "".join(p.stderr),
-        )
+class AuditTest(BaseTest):
+    TEST_FILE_PY = os.path.abspath(
+        os.path.join(os.path.dirname(__file__), "audit-tests.py")
+    )
 
     def test_basic(self):
         self.do_test("test_basic")
diff --git a/tests/test_spans.py b/tests/test_spans.py
new file mode 100644
index 0000000..9d764fd
--- /dev/null
+++ b/tests/test_spans.py
@@ -0,0 +1,36 @@
+import os
+
+from .base import BaseTest
+
+
+class SubscribeTest(BaseTest):
+    TEST_FILE_PY = os.path.abspath(
+        os.path.join(os.path.dirname(__file__), "span-tests.py")
+    )
+
+    def test_properties(self):
+        self.do_test("test_properties")
+
+    def test_started_ended(self):
+        self.do_test("test_started_ended")
+
+    def test_started_ended_contextmanager(self):
+        self.do_test("test_started_ended_contextmanager")
+
+    def test_lifecycle_events(self):
+        self.do_test("test_lifecycle_events")
+
+    def test_lifecycle_events_contextmanager(self):
+        self.do_test("test_lifecycle_events_contextmanager")
+
+    def test_lifecycle_events_data(self):
+        self.do_test("test_lifecycle_events_data")
+
+    def test_end_before_start(self):
+        self.do_test("test_end_before_start")
+
+    def test_custom_message(self):
+        self.do_test("test_custom_message")
+
+    def test_annotate_message(self):
+        self.do_test("test_custom_message")
diff --git a/tests/test_subscribe.py b/tests/test_subscribe.py
new file mode 100644
index 0000000..6b4fbb7
--- /dev/null
+++ b/tests/test_subscribe.py
@@ -0,0 +1,15 @@
+import os
+
+from .base import BaseTest
+
+
+class SubscribeTest(BaseTest):
+    TEST_FILE_PY = os.path.abspath(
+        os.path.join(os.path.dirname(__file__), "subscribe-tests.py")
+    )
+
+    def test_basic(self):
+        self.do_test("test_basic")
+
+    def test_multiple_hooks(self):
+        self.do_test("test_multiple_hooks")