feat: combat system — damage calc, co-op bonus, flee, monster AI

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

combat/combat_test.go

@@ -0,0 +1,59 @@
+package combat
+
+import (
+	"testing"
+
+	"github.com/tolelom/catacombs/entity"
+)
+
+func TestCalcDamage(t *testing.T) {
+	dmg := CalcDamage(12, 1, 1.0)
+	if dmg < 9 || dmg > 13 {
+		t.Errorf("Damage out of expected range: got %d, want 9~13", dmg)
+	}
+}
+
+func TestCalcDamageMinimum(t *testing.T) {
+	dmg := CalcDamage(1, 100, 1.0)
+	if dmg != 1 {
+		t.Errorf("Minimum damage: got %d, want 1", dmg)
+	}
+}
+
+func TestCoopBonus(t *testing.T) {
+	attackers := []AttackIntent{
+		{PlayerATK: 12, TargetIdx: 0, Multiplier: 1.0, IsAoE: false},
+		{PlayerATK: 15, TargetIdx: 0, Multiplier: 1.0, IsAoE: false},
+	}
+	results := ResolveAttacks(attackers, []*entity.Monster{entity.NewMonster(entity.MonsterSlime, 1)})
+	if !results[1].CoopApplied {
+		t.Error("Second attacker should get co-op bonus")
+	}
+}
+
+func TestAoENoCoopBonus(t *testing.T) {
+	attackers := []AttackIntent{
+		{PlayerATK: 12, TargetIdx: 0, Multiplier: 1.0, IsAoE: false},
+		{PlayerATK: 20, TargetIdx: -1, Multiplier: 0.8, IsAoE: true},
+	}
+	monsters := []*entity.Monster{
+		entity.NewMonster(entity.MonsterSlime, 1),
+		entity.NewMonster(entity.MonsterSlime, 1),
+	}
+	results := ResolveAttacks(attackers, monsters)
+	if results[0].CoopApplied {
+		t.Error("AoE should not trigger co-op bonus")
+	}
+}
+
+func TestFleeChance(t *testing.T) {
+	successes := 0
+	for i := 0; i < 100; i++ {
+		if AttemptFlee() {
+			successes++
+		}
+	}
+	if successes < 20 || successes > 80 {
+		t.Errorf("Flee success rate suspicious: %d/100", successes)
+	}
+}