Tests

A Test runs functions in an interpreter, without starting the game, and checks what they did:

Type SiegeState { wave: int = 0 }
Storage game: SiegeState

Function next_wave {
  game.wave += 1
  for i in 1..game.wave * 2 {
    As(@e[tag=siege.spawn]).At(@s) {
      /summon zombie ~ ~ ~ {Tags:["siege.enemy"]}
    }
  }
}

Function fib(n: int): int {
  if (n < 2) {
    return n
  }
  return fib(n - 1) + fib(n - 2)
}

Test second_wave_spawns_four {
  setup {
    game.wave = 1
    /summon marker 0 64 0 {Tags:["siege.spawn"]}
  }
  run next_wave()
  expect game.wave == 2
  expect count(@e[tag=siege.enemy]) == 4
}

Test fibonacci {
  expect fib(10) == 55
}

Part	Does
`setup { }`	function code and commands that run first. Its `let` variables are in scope for the lines after it.
`run f()`	calls a function
`expect cond`	checks a condition. The test stops at the first one that fails, and a failed comparison shows both sides.

Each test starts from a fresh world after the pack's load functions. run and expect lines can come in any order after setup.

mms test runs every test, the web editor's Tests tab runs them after every edit, and VS Code lists them in its Testing view. The Functions guide lists what the interpreter can run.