program main
  fn fixture_path() -> string
    string "slovo-exp3-host-io.txt"
  fn write_fixture() -> i32
    call std.fs.write_text
      call fixture_path
      string "host io"
  fn read_fixture() -> string
    call std.fs.read_text
      call fixture_path
  fn missing_env() -> string
    call std.env.get
      string "SLOVO_EXP3_MISSING"
  fn arg_count_plus_one() -> i32
    binary +
      call std.process.argc
      int 1
  fn main() -> i32
    call std.io.eprint
      string "exp-3 host io"
    call std.io.print_string
      call std.process.arg
        int 0
    call std.io.print_string
      call read_fixture
    call std.fs.write_text
      call fixture_path
      string "host io"
  test "missing env returns empty string"
    binary =
      call missing_env
      string ""
  test "argc is not negative"
    binary <
      int 0
      call arg_count_plus_one
  test "write text returns success"
    binary =
      call write_fixture
      int 0
  test "read text returns written text"
    binary =
      call read_fixture
      string "host io"