From 66b550b9f00b6c8600fad60572de166982a024bd Mon Sep 17 00:00:00 2001
From: PhallenTree <168426989+PhallenTree@users.noreply.github.com>
Date: Fri, 6 Mar 2026 19:47:19 +0000
Subject: [PATCH] Fixes Trump Card's power calculation using its own PP when
 called by another move (#9445)

---
 src/battle_util.c                    |  2 +-
 test/battle/move_effect/trump_card.c | 77 +++++++++++++++++++++++++++-
 2 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/src/battle_util.c b/src/battle_util.c
index cf94c40a88..93941198ac 100644
--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -6357,7 +6357,7 @@ static inline u32 CalcMoveBasePower(struct BattleContext *ctx)
             basePower *= 2;
         break;
     case EFFECT_TRUMP_CARD:
-        i = GetMoveSlot(gBattleMons[battlerAtk].moves, move);
+        i = GetMoveSlot(gBattleMons[battlerAtk].moves, ctx->chosenMove);
         if (i != MAX_MON_MOVES)
         {
             if (gBattleMons[battlerAtk].pp[i] >= ARRAY_COUNT(sTrumpCardPowerTable))
diff --git a/test/battle/move_effect/trump_card.c b/test/battle/move_effect/trump_card.c
index 21b5c48ca3..1fa9850a4c 100644
--- a/test/battle/move_effect/trump_card.c
+++ b/test/battle/move_effect/trump_card.c
@@ -1,4 +1,79 @@
 #include "global.h"
 #include "test/battle.h"
 
-TO_DO_BATTLE_TEST("TODO: Write Trump Card (Move Effect) test titles")
+ASSUMPTIONS
+{
+    ASSUME(GetMoveEffect(MOVE_TRUMP_CARD) == EFFECT_TRUMP_CARD);
+}
+
+SINGLE_BATTLE_TEST("Trump Card increases in power if its PP is low", s16 damage)
+{
+    // pp + 1 is assigned as the move's PP as it will be reduced before its base power is determined
+    u32 pp;
+
+    PARAMETRIZE { pp = 4; } // 40 power
+    PARAMETRIZE { pp = 3; } // 50 power
+    PARAMETRIZE { pp = 2; } // 60 power
+    PARAMETRIZE { pp = 1; } // 80 power
+    PARAMETRIZE { pp = 0; } // 200 power
+
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET) { MovesWithPP({MOVE_TRUMP_CARD, pp + 1}); }
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { MOVE(player, MOVE_TRUMP_CARD); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_TRUMP_CARD, player);
+        HP_BAR(opponent, captureDamage: &results[i].damage);
+    } FINALLY {
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(1.25), results[1].damage);
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(1.5), results[2].damage);
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(2.0), results[3].damage);
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(5.0), results[4].damage);
+    }
+}
+
+SINGLE_BATTLE_TEST("Trump Card doesn't increase in power if its PP is low when called by a different move", s16 damage)
+{
+    u32 pp;
+
+    PARAMETRIZE { pp = 4; } // would be 40 power
+    PARAMETRIZE { pp = 0; } // would be 200 power
+
+    GIVEN {
+        ASSUME(GetMoveEffect(MOVE_SLEEP_TALK) == EFFECT_SLEEP_TALK);
+        PLAYER(SPECIES_WOBBUFFET) { MovesWithPP({MOVE_TRUMP_CARD, pp}, {MOVE_SLEEP_TALK, 10}); Status1(STATUS1_SLEEP); }
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { MOVE(player, MOVE_SLEEP_TALK); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_SLEEP_TALK, player);
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_TRUMP_CARD, player);
+        HP_BAR(opponent, captureDamage: &results[i].damage);
+    } FINALLY {
+        EXPECT_EQ(results[0].damage, results[1].damage);
+    }
+}
+
+SINGLE_BATTLE_TEST("Trump Card increases in power if the move that called it has low PP", s16 damage)
+{
+    // pp + 1 is assigned as the move's PP as it will be reduced before its base power is determined
+    u32 pp;
+
+    PARAMETRIZE { pp = 4; } // 40 power
+    PARAMETRIZE { pp = 0; } // 200 power
+
+    GIVEN {
+        ASSUME(GetMoveEffect(MOVE_SLEEP_TALK) == EFFECT_SLEEP_TALK);
+        PLAYER(SPECIES_WOBBUFFET) { MovesWithPP({MOVE_TRUMP_CARD, 5}, {MOVE_SLEEP_TALK, pp + 1}); Status1(STATUS1_SLEEP); }
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { MOVE(player, MOVE_SLEEP_TALK); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_SLEEP_TALK, player);
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_TRUMP_CARD, player);
+        HP_BAR(opponent, captureDamage: &results[i].damage);
+    } FINALLY {
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(5.0), results[1].damage);
+    }
+}