def test_promptYes(self):
        """
        L{ConsoleUI.prompt} writes a message to the console, then reads a line.
        If that line is 'yes', then it returns a L{Deferred} that fires with
        True.
        """
        for okYes in [b'yes', b'Yes', b'yes\n']:
            self.newFile([okYes])
            l = []
            self.ui.prompt("Hello, world!").addCallback(l.append)
            self.assertEqual(["Hello, world!"], self.fakeFile.outchunks)
            self.assertEqual([True], l)
            self.assertTrue(self.fakeFile.closed)

        L{ConsoleUI.prompt} writes a message to the console, then reads a line.
        If that line is 'yes', then it returns a L{Deferred} that fires with
        True.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_knownhosts.py