file-transfer: writing tests and ensuring that all is going well

file_transfer/send_file.py

@@ -1,4 +1,4 @@
-if __name__ == "__main__":
+def run_script():
     import socket  # Import socket module
 
     ONE_CONNECTION_ONLY = (
@@ -36,3 +36,7 @@
 
     sock.shutdown(1)
     sock.close()
+
+
+if __name__ == "__main__":  # pragma: no cover
+    run_script()

file_transfer/tests/test_send_file.py

@@ -0,0 +1,32 @@
+from unittest.mock import patch, Mock
+
+
+from file_transfer.send_file import run_script as send_file
+
+
+@patch("socket.socket")
+@patch("builtins.open")
+def test_send_file_running_as_expected(file, sock):
+    # ===== initialization =====
+    conn = Mock()
+    sock.return_value.accept.return_value = conn, Mock()
+    f = iter([1, None])
+    file.return_value.__enter__.return_value.read.side_effect = lambda _: next(f)
+
+    # ===== invoke =====
+    send_file()
+
+    # ===== ensurance =====
+    sock.assert_called_once()
+    sock.return_value.bind.assert_called_once()
+    sock.return_value.listen.assert_called_once()
+    sock.return_value.accept.assert_called_once()
+    conn.recv.assert_called_once()
+
+    file.return_value.__enter__.assert_called_once()
+    file.return_value.__enter__.return_value.read.assert_called()
+
+    conn.send.assert_called_once()
+    conn.close.assert_called_once()
+    sock.return_value.shutdown.assert_called_once()
+    sock.return_value.close.assert_called_once()