test_marks.json
 1{"Put":{"state":"line one\nline ˇtwo\nline three"}}
 2{"Key":"m"}
 3{"Key":"a"}
 4{"Key":"l"}
 5{"Key":"'"}
 6{"Key":"a"}
 7{"Get":{"state":"line one\nˇline two\nline three","mode":"Normal"}}
 8{"Key":"`"}
 9{"Key":"a"}
10{"Get":{"state":"line one\nline ˇtwo\nline three","mode":"Normal"}}
11{"Key":"^"}
12{"Key":"d"}
13{"Key":"`"}
14{"Key":"a"}
15{"Get":{"state":"line one\nˇtwo\nline three","mode":"Normal"}}