tests: add test for the demo example

Makefile

@@ -4,7 +4,7 @@ python=python3
 default: check lint
 
 check: $(venv_dir)/bin/pytest
-	$(venv_dir)/bin/pytest -vs tests
+	$(venv_dir)/bin/pytest -vs tests $(pytest_args)
 
 lint: $(venv_dir)/bin/flake8
 	$(venv_dir)/bin/flake8 . --show-source --statistics

tests/conftest.py

@@ -0,0 +1,4 @@
+from logging import DEBUG, basicConfig
+
+
+basicConfig(level=DEBUG)

tests/test_demo.py

@@ -0,0 +1,109 @@
+from aiohttp import ClientSession
+from asyncio import run
+from collections import namedtuple
+from contextlib import contextmanager
+from logging import getLogger
+from pathlib import Path
+from pytest import fixture
+import re
+from socket import socket
+from subprocess import Popen, DEVNULL, PIPE
+from threading import Thread
+from time import sleep
+
+
+test_port = 8080
+
+logger = getLogger(__name__)
+
+
+@fixture(scope='session')
+def demo_executable():
+    project_dir = Path(__file__).resolve().parent.parent
+    demo_path = project_dir / 'demo.py'
+    assert demo_path.is_file()
+    return demo_path
+
+
+def tcp_connect_works(host, port):
+    with socket() as s:
+        try:
+            s.connect((host, port))
+            return True
+        except ConnectionRefusedError:
+            return False
+
+
+def read_output(stream, lines, label):
+    try:
+        for line in stream:
+            line = line.decode('utf-8').rstrip()
+            lines.append(line)
+            logger.info('%s: %s', label, line)
+    finally:
+        stream.close()
+
+
+RunningDemo = namedtuple('RunningDemo', 'process stdout_lines stderr_lines')
+
+
+@fixture
+def run_demo(demo_executable):
+    @contextmanager
+    def do_run_demo():
+        cmd = ['python3', str(demo_executable)]
+        with Popen(cmd, stdin=DEVNULL, stdout=PIPE, stderr=PIPE) as process:
+            stdout_lines = []
+            stderr_lines = []
+            stdout_thread = Thread(target=read_output, args=(process.stdout, stdout_lines, 'stdout'), daemon=True)
+            stderr_thread = Thread(target=read_output, args=(process.stderr, stderr_lines, 'stderr'), daemon=True)
+            stdout_thread.start()
+            stderr_thread.start()
+            try:
+                logger.info('Started command %s as pid %d', cmd, process.pid)
+
+                # Wait for the server to start up and accept connections
+                for _ in range(100):
+                    sleep(0.01)
+                    assert process.poll() is None
+                    if tcp_connect_works('localhost', test_port):
+                        break
+                else:
+                    raise RuntimeError('Server did not start')
+
+                yield RunningDemo(process, stdout_lines, stderr_lines)
+            finally:
+                if process.poll() is not None:
+                    logger.info('Process %d has already terminated with return code %d', process.pid, process.returncode)
+                else:
+                    # Shut down the server
+                    logger.info('Terminating process %d', process.pid)
+                    process.terminate()
+                    process.wait()
+                    logger.info('Process %d terminated with return code %d', process.pid, process.returncode)
+                # Wait for the threads to finish
+                stdout_thread.join()
+                stderr_thread.join()
+    return do_run_demo
+
+
+def test_hello_world(run_demo):
+    async def fetch():
+        async with ClientSession() as session:
+            async with session.get(f'http://localhost:{test_port}/') as response:
+                return await response.text()
+
+    with run_demo() as demo:
+        text = run(fetch())
+        assert text == 'Hello, world!\n'
+
+    lines = [line for line in demo.stderr_lines if 'DEBUG' not in line]
+    assert len(lines) == 3
+    m0 = re.match(r'.*  INFO: \[req:([a-zA-Z0-9]+)\] Processing GET / \(__main__:hello\)$', lines[0])
+    m1 = re.match(r'.*  INFO: \[req:([a-zA-Z0-9]+)\] Doing something$', lines[1])
+    m2 = re.match(r'.*  INFO: \[req:([a-zA-Z0-9]+)\] .*GET /.* 200 .*$', lines[2])
+    assert m0
+    assert m1
+    assert m2
+    assert m0.groups() == m1.groups()
+    assert m0.groups() == m2.groups()