diff --git a/test.py b/test.py
new file mode 100755
index 0000000..c45d97d
--- /dev/null
+++ b/test.py
@@ -0,0 +1,139 @@
+#!/usr/bin/env python3
+import unittest
+from checklib import Result, Check
+from contextlib import redirect_stdout
+from textwrap import dedent
+import io
+import sys
+
+def make_check(
+		result=Result.UNKNOWN,
+		short_message='Just a message',
+		long_message = None):
+	class Result(Check):
+		def check(self):
+			self.short_status = short_message
+			self.result=result
+			if long_message is not None:
+				self.long_status = long_message
+	return Result
+
+class DefaultCheck(Check): pass
+class ExceptionInInit(Check):
+	def __init__(self):
+		raise ValueError('whatever')
+
+class ExceptionInCheck(Check):
+	def check(self):
+		raise ValueError('whatever')
+
+class ExitInInit(Check):
+	def __init__(self):
+		sys.exit(42)
+
+class ExitInCheck(Check):
+	def check(self):
+		sys.exit(42)
+
+class T(unittest.TestCase):
+	def setUp(self):
+		self.passing_check = make_check(Result.OK)
+		self.warning_check = make_check(Result.WARNING)
+		self.critical_check = make_check(Result.CRITICAL)
+		self.unknown_check = make_check(Result.UNKNOWN)
+		self.check_without_status = make_check(Result.OK, short_message = None)
+
+		# Multiline status:
+		# Ref: IT Crowd :-)
+		self.short_message = 'Subject: Fire!'
+		self.long_message = dedent('''\
+			Dear Sir / Madam,
+			
+			I am writing to inform
+			you of a fire, that has broken…
+			No, that\'s too formal.''')
+		self.multiline_check = make_check(Result.OK, self.short_message, self.long_message)
+		# Other checks are given as separate classes.
+		self.all_checks = [
+			self.unknown_check,
+			ExceptionInCheck,
+			ExceptionInInit,
+			ExitInCheck,
+			ExitInInit,
+			DefaultCheck,
+			self.check_without_status,
+			self.multiline_check,
+			self.passing_check,
+			self.warning_check,
+			self.critical_check,
+		]
+	
+	def test_run_exits(self):
+		for check in self.all_checks:
+			with self.subTest(check=check):
+				with self.assertRaises(SystemExit):
+					check.run()
+	
+	def test_correct_return_code(self):
+		expected_results = {
+			Result.UNKNOWN: [
+				self.unknown_check,
+				ExceptionInCheck,
+				ExceptionInInit,
+				ExitInCheck,
+				ExitInInit,
+				DefaultCheck,
+				self.check_without_status,
+				],
+			Result.OK: [
+				self.multiline_check,
+				self.passing_check,
+				],
+			Result.WARNING: [
+				self.warning_check,
+				],
+			Result.CRITICAL: [
+				self.critical_check,
+				],
+			}
+
+		for result, checks in expected_results.items():
+			for check in checks:
+				with self.subTest(check=check, expected_result=result):
+					try:
+						check.run()
+					except SystemExit as e:
+						self.assertEqual(e.code, result.value)
+	
+	def test_something_output(self):
+		for check in self.all_checks:
+			with self.subTest(check=check):
+				with redirect_stdout(io.StringIO()) as output:
+					try:
+						check.run()
+					except SystemExit:
+						pass
+				output = output.getvalue()
+				assert len(output) > 0
+				assert '\n' in output
+	
+	def test_correct_output(self):
+		"""
+		The multiline status must contain both messages verbatim.
+		"""
+		with redirect_stdout(io.StringIO()) as output:
+			try:
+				self.multiline_check.run()
+			except SystemExit:
+				pass
+		output = output.getvalue()
+		self.assertIn(self.short_message, output)
+		self.assertIn(self.long_message, output)
+
+
+
+
+
+
+if __name__ == '__main__':
+	unittest.main()