diff --git a/test/battle/move_effects_combined/toxic_thread.c b/test/battle/move_effects_combined/toxic_thread.c
new file mode 100644
index 0000000000..c946619cd8
--- /dev/null
+++ b/test/battle/move_effects_combined/toxic_thread.c
@@ -0,0 +1,108 @@
+#include "global.h"
+#include "test/battle.h"
+
+ASSUMPTIONS
+{
+    ASSUME(GetMoveEffect(MOVE_TOXIC_THREAD) == EFFECT_TOXIC_THREAD);
+}
+
+SINGLE_BATTLE_TEST("Toxic Thread both reduces speed and inflicts Poison")
+{
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { MOVE(player, MOVE_TOXIC_THREAD); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_TOXIC_THREAD, player);
+        ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_STATS_CHANGE, opponent);
+        ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponent);
+        STATUS_ICON(opponent, poison: TRUE);
+    } THEN {
+        EXPECT_EQ(opponent->statStages[STAT_SPEED], DEFAULT_STAT_STAGE - 1);
+    }
+}
+
+SINGLE_BATTLE_TEST("Toxic Thread still inflicts Poison if speed can't go lower")
+{
+    KNOWN_FAILING; // #7243
+    GIVEN {
+        ASSUME(GetMoveEffect(MOVE_SCARY_FACE) == EFFECT_SPEED_DOWN_2);
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { MOVE(player, MOVE_SCARY_FACE); }
+        TURN { MOVE(player, MOVE_SCARY_FACE); }
+        TURN { MOVE(player, MOVE_SCARY_FACE); }
+        TURN { MOVE(player, MOVE_TOXIC_THREAD); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_SCARY_FACE, player);
+        ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_STATS_CHANGE, opponent);
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_SCARY_FACE, player);
+        ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_STATS_CHANGE, opponent);
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_SCARY_FACE, player);
+        ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_STATS_CHANGE, opponent);
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_TOXIC_THREAD, player);
+        NOT ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_STATS_CHANGE, opponent);
+        ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponent);
+        STATUS_ICON(opponent, poison: TRUE);
+    } THEN {
+        EXPECT_EQ(opponent->statStages[STAT_SPEED], DEFAULT_STAT_STAGE - 6);
+    }
+}
+
+SINGLE_BATTLE_TEST("Toxic Thread still inflicts Poison if speed can't be lowered")
+{
+    KNOWN_FAILING; // #7243
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_REGICE) { Ability(ABILITY_CLEAR_BODY); }
+    } WHEN {
+        TURN { MOVE(player, MOVE_TOXIC_THREAD); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_TOXIC_THREAD, player);
+        NOT ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_STATS_CHANGE, opponent);
+        ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponent);
+        STATUS_ICON(opponent, poison: TRUE);
+    } THEN {
+        EXPECT_EQ(opponent->statStages[STAT_SPEED], DEFAULT_STAT_STAGE);
+    }
+}
+
+SINGLE_BATTLE_TEST("Toxic Thread still lowers speed if the target can't be Poisoned")
+{
+    GIVEN {
+        ASSUME(gSpeciesInfo[SPECIES_BRONZOR].types[0] == TYPE_STEEL || gSpeciesInfo[SPECIES_BRONZOR].types[1] == TYPE_STEEL);
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_BRONZOR);
+    } WHEN {
+        TURN { MOVE(player, MOVE_TOXIC_THREAD); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_TOXIC_THREAD, player);
+        ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_STATS_CHANGE, opponent);
+        NOT ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponent);
+    } THEN {
+        EXPECT_EQ(opponent->statStages[STAT_SPEED], DEFAULT_STAT_STAGE - 1);
+    }
+}
+
+SINGLE_BATTLE_TEST("Toxic Thread still lowers speed if the target is already Poisoned")
+{
+    GIVEN {
+        ASSUME(GetMoveEffect(MOVE_POISON_POWDER) == EFFECT_NON_VOLATILE_STATUS);
+        ASSUME(GetMoveNonVolatileStatus(MOVE_POISON_POWDER) == MOVE_EFFECT_POISON);
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { MOVE(player, MOVE_POISON_POWDER); }
+        TURN { MOVE(player, MOVE_TOXIC_THREAD); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_POISON_POWDER, player);
+        ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponent);
+        STATUS_ICON(opponent, poison: TRUE);
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_TOXIC_THREAD, player);
+        ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_STATS_CHANGE, opponent);
+    } THEN {
+        EXPECT_EQ(opponent->statStages[STAT_SPEED], DEFAULT_STAT_STAGE - 1);
+    }
+}