How to unit-test multi-line prompts

I'm using a mock PipeInput with .send_text to simulate user input. Recently, I've switched to multi-line inputs which can be terminated by either Meta+Enter or Esc then Enter. What string should I pass to .send_text to replicate that?

I've tried the ASCII code for Esc:

mock_input.send_text("First Reply\x1B\nSecond Reply\x1B\n")

But the program still hangs when prompt() is called

Fixture created like this:

@pytest.fixture
def mock_input():
    with create_pipe_input() as pipe_input:
        with create_app_session(input=pipe_input, output=DummyOutput()):
            yield pipe_input

Called like in this in code under test:

    msg = prompt("> ", multiline=True)

Start with the create_pipe_input fixture and the send_text call shown in the issue, then trace how prompt(..., multiline=True) interprets termination input. Confirm the correct sequence for both Meta+Enter and Esc followed by Enter, and add or update a focused unit test demonstrating that prompt() returns instead of hanging.