Missing feature `close_input`

[tompng]

Currently, it is impossible to perform this test in yamatanooroti.

start_terminal(10, 10, command)
write("1+2.ab")
assert_screen("> 1+2.ab\n     .abs\n     .abs2")
close_input # Close input stream. This API does not exist. There are no alternatives.
assert_screen("> 1+2.ab\n=> undefined method `ab' for an instance of Integer (NoMethodError)")
close # Terminates process. Always call this after assert_screen.

API to close STDIN of the test target process is missing.