Add variable question distractor pools

tests/choice_pool_test.gd

@@ -0,0 +1,59 @@
+extends SceneTree
+
+var failures := 0
+
+
+func _initialize() -> void:
+	var service = load("res://scripts/autoload/block_session_service.gd").new()
+	var question := _question(9)
+	var prepared: Dictionary = service._prepare_question_choices(question.duplicate(true))
+	_check_presented(prepared)
+
+	var stable: Dictionary = service._prepare_question_choices(prepared.duplicate(true))
+	_assert(stable.get("presented_choices", []) == prepared.get("presented_choices", []), "session choices must remain stable")
+
+	var observed_sets := {}
+	for iteration in range(40):
+		var rerolled: Dictionary = service._prepare_question_choices(question.duplicate(true))
+		_check_presented(rerolled)
+		var ids := _ids(rerolled.get("presented_choices", []))
+		ids.sort()
+		observed_sets[",".join(ids)] = true
+	_assert(observed_sets.size() > 1, "future sessions should be able to present different distractors")
+
+	var legacy: Dictionary = service._prepare_question_choices(_question(5))
+	_check_presented(legacy)
+	_assert(_ids(legacy.get("presented_choices", [])).size() == 5, "legacy five-choice questions must show all choices")
+	service.free()
+	quit(1 if failures > 0 else 0)
+
+
+func _question(count: int) -> Dictionary:
+	var choices: Array = []
+	for index in range(count):
+		choices.append({"id": String.chr(65 + index), "text": "Choice %d" % index})
+	return {"choices": choices, "correct_choice_id": "A"}
+
+
+func _check_presented(question: Dictionary) -> void:
+	var ids := _ids(question.get("presented_choices", []))
+	_assert(ids.size() == 5, "exactly five choices must be presented")
+	_assert(ids.has("A"), "the correct answer must be presented")
+	var unique := {}
+	for id in ids:
+		unique[id] = true
+	_assert(unique.size() == ids.size(), "presented choices must be unique")
+
+
+func _ids(choices: Array) -> Array:
+	var ids: Array = []
+	for choice in choices:
+		ids.append(str(choice.get("id", "")))
+	return ids
+
+
+func _assert(condition: bool, message: String) -> void:
+	if condition:
+		return
+	failures += 1
+	push_error(message)

tests/choice_pool_test.gd.uid

@@ -0,0 +1 @@
+uid://dphnt1gskhhna