Add a testing helper for serving HTTP locally.

tests/helpers/http.py

@@ -0,0 +1,61 @@
+import http.server
+import threading
+
+
+class Server:
+    """Wraps an http.server.HTTPServer in a thread."""
+
+    def __init__(self, handler, host='', port=8000):
+        self.handler = handler
+        self._addr = (host, port)
+        self._server = None
+        self._thread = None
+
+    @property
+    def address(self):
+        host, port = self._addr
+        if host == '':
+            host = 'localhost'
+        return '{}:{}'.format(host, port)
+
+    def start(self):
+        if self._server is not None:
+            raise RuntimeError('already started')
+        self._server = http.server.HTTPServer(self._addr, self.handler)
+        self._thread = threading.Thread(
+                target=lambda: self._server.serve_forever())
+        self._thread.start()
+
+    def stop(self):
+        if self._server is None:
+            raise RuntimeError('not running')
+        self._server.shutdown()
+        self._thread.join()
+        self._server.server_close()
+        self._thread = None
+        self._server = None
+
+    def __enter__(self):
+        self.start()
+        return self
+
+    def __exit__(self, *args):
+        self.stop()
+
+
+def json_file_handler(data):
+    """Return an HTTP handler that always serves the given JSON bytes."""
+
+    class HTTPHandler(http.server.BaseHTTPRequestHandler):
+        def do_GET(self):
+            self.send_response(200)
+            self.send_header('Content-Type', b'application/json')
+            self.send_header('Content-Length',
+                             str(len(data)).encode('ascii'))
+            self.end_headers()
+            self.wfile.write(data)
+
+        def log_message(self, *args, **kwargs):
+            pass
+
+    return HTTPHandler