diff --git a/tests/dungeon-wilderness-animations.test.ts b/tests/dungeon-wilderness-animations.test.ts
index b5510cc..ec61f2e 100644
--- a/tests/dungeon-wilderness-animations.test.ts
+++ b/tests/dungeon-wilderness-animations.test.ts
@@ -104,6 +104,63 @@ describe('Dungeon & Wilderness Illumination & Animated Tile Sequences (Issue #39
       expect(p1).toBeGreaterThanOrEqual(0)
       expect(p1).toBeLessThan(duration)
     })
+
+    it('prevents sprite coordinate drift across frame transitions and loops', () => {
+      const frames: AnimatedObjectFrame[] = [
+        { frame: dummyAtlasFrame(0), page: 0, offsetX: -10, offsetY: -20 },
+        { frame: dummyAtlasFrame(1), page: 0, offsetX: -15, offsetY: -25 },
+        { frame: dummyAtlasFrame(2), page: 0, offsetX: -8, offsetY: -18 },
+      ]
+      const obj: ObjectDrawable = {
+        token: 'TO',
+        frame: frames[0]!.frame,
+        x: 100 + frames[0]!.offsetX,
+        y: 200 + frames[0]!.offsetY,
+        depth: 60,
+        page: 0,
+        baseX: 100,
+        baseY: 200,
+        animatedFrames: frames,
+        frameDurationMs: 100,
+        cycleAnim: true,
+        currentFrameIndex: 0,
+      }
+
+      for (let clock = 0; clock <= 3000; clock += 50) {
+        updateAnimatedObject(obj, clock)
+        const expectedFrameIdx = Math.floor(clock / 100) % 3
+        expect(obj.currentFrameIndex).toBe(expectedFrameIdx)
+        const expectedFrame = frames[expectedFrameIdx]!
+        expect(obj.x).toBe(100 + expectedFrame.offsetX)
+        expect(obj.y).toBe(200 + expectedFrame.offsetY)
+      }
+    })
+
+    it('safely handles degenerate frame inputs (empty, single frame, zero/negative duration)', () => {
+      const singleFrameObj: ObjectDrawable = {
+        token: 'TO',
+        frame: dummyAtlasFrame(0),
+        x: 100,
+        y: 200,
+        depth: 60,
+        page: 0,
+        baseX: 100,
+        baseY: 200,
+        animatedFrames: [{ frame: dummyAtlasFrame(0), page: 0, offsetX: 0, offsetY: 0 }],
+        frameDurationMs: 80,
+        currentFrameIndex: 0,
+      }
+      expect(updateAnimatedObject(singleFrameObj, 1000)).toBe(false)
+      expect(singleFrameObj.currentFrameIndex).toBe(0)
+
+      const zeroDurationObj = createTestIlluminationDrawable('TO', 5, 0, true)
+      expect(updateAnimatedObject(zeroDurationObj, 120)).toBe(true)
+      expect(zeroDurationObj.currentFrameIndex).toBe(3)
+
+      const negClockObj = createTestIlluminationDrawable('TO', 5, 40, true)
+      expect(updateAnimatedObject(negClockObj, -100)).toBe(false)
+      expect(negClockObj.currentFrameIndex).toBe(0)
+    })
   })
 
   describe('DT1 animated tile serialization and unpacking parity', () => {
@@ -166,7 +223,7 @@ describe('Dungeon & Wilderness Illumination & Animated Tile Sequences (Issue #39
 
     it('verifies town scene (towne1) preserves all animated objects', () => {
       const townPath = join(packsDir, 'act1/1-act-1-town-towne1/scene.json')
-      if (!existsSync(townPath)) return
+      expect(existsSync(townPath)).toBe(true)
 
       const scene = JSON.parse(readFileSync(townPath, 'utf8'))
       const objects = scene.objects as any[]
@@ -190,13 +247,13 @@ describe('Dungeon & Wilderness Illumination & Animated Tile Sequences (Issue #39
 
     it('verifies Cave (Level 10) packs have animated illumination objects', () => {
       const act1Dir = join(packsDir, 'act1')
-      if (!existsSync(act1Dir)) return
+      expect(existsSync(act1Dir)).toBe(true)
 
       const caveDirs = readdirSync(act1Dir).filter(name => name.startsWith('10-act-1-cave'))
       expect(caveDirs.length).toBeGreaterThan(0)
       for (const d of caveDirs) {
         const scenePath = join(act1Dir, d, 'scene.json')
-        if (!existsSync(scenePath)) continue
+        expect(existsSync(scenePath)).toBe(true)
         const scene = JSON.parse(readFileSync(scenePath, 'utf8'))
         const illumination = (scene.objects as any[]).filter(o =>
           o.token && PERSISTENT_ILLUMINATION_TOKENS.has(o.token.trim().toUpperCase())
@@ -214,7 +271,7 @@ describe('Dungeon & Wilderness Illumination & Animated Tile Sequences (Issue #39
 
     it('verifies Catacombs (Level 34) packs have animated candles (A1, A2) and fires (BF, BR)', () => {
       const act1Dir = join(packsDir, 'act1')
-      if (!existsSync(act1Dir)) return
+      expect(existsSync(act1Dir)).toBe(true)
 
       const catacombsDirs = readdirSync(act1Dir).filter(name => name.startsWith('34-act-1-catacombs'))
       expect(catacombsDirs.length).toBeGreaterThan(0)
@@ -222,7 +279,7 @@ describe('Dungeon & Wilderness Illumination & Animated Tile Sequences (Issue #39
       let totalCandlesOrFires = 0
       for (const d of catacombsDirs) {
         const scenePath = join(act1Dir, d, 'scene.json')
-        if (!existsSync(scenePath)) continue
+        expect(existsSync(scenePath)).toBe(true)
         const scene = JSON.parse(readFileSync(scenePath, 'utf8'))
         const items = (scene.objects as any[]).filter(o =>
           o.token && ['A1', 'A2', 'BF', 'BR', 'TO'].includes(o.token.trim().toUpperCase())
@@ -241,13 +298,13 @@ describe('Dungeon & Wilderness Illumination & Animated Tile Sequences (Issue #39
 
     it('verifies Wilderness and Crypt maps contain cycleAnim=true on illumination objects', () => {
       const act1Dir = join(packsDir, 'act1')
-      if (!existsSync(act1Dir)) return
+      expect(existsSync(act1Dir)).toBe(true)
 
       const cryptDirs = readdirSync(act1Dir).filter(name => name.startsWith('18-act-1-crypt') || name.startsWith('19-act-1-crypt'))
       expect(cryptDirs.length).toBeGreaterThan(0)
       for (const d of cryptDirs) {
         const scenePath = join(act1Dir, d, 'scene.json')
-        if (!existsSync(scenePath)) continue
+        expect(existsSync(scenePath)).toBe(true)
         const scene = JSON.parse(readFileSync(scenePath, 'utf8'))
         const items = (scene.objects as any[]).filter(o =>
           o.token && PERSISTENT_ILLUMINATION_TOKENS.has(o.token.trim().toUpperCase())
@@ -262,7 +319,7 @@ describe('Dungeon & Wilderness Illumination & Animated Tile Sequences (Issue #39
 
     it('verifies DT1 animated tile sequences in scenes that contain animated tiles', () => {
       const act4Dir = join(packsDir, 'act4')
-      if (!existsSync(act4Dir)) return
+      expect(existsSync(act4Dir)).toBe(true)
 
       // River of flame (Level 107) and Chaos Sanctuary (Level 108) have animated lava tiles
       const chaosDirs = readdirSync(act4Dir).filter(name => name.startsWith('108-act-4-diablo') || name.startsWith('107-act-4-lava'))
@@ -270,7 +327,7 @@ describe('Dungeon & Wilderness Illumination & Animated Tile Sequences (Issue #39
       let totalAnimatedTiles = 0
       for (const d of chaosDirs) {
         const scenePath = join(act4Dir, d, 'scene.json')
-        if (!existsSync(scenePath)) continue
+        expect(existsSync(scenePath)).toBe(true)
         const scene = JSON.parse(readFileSync(scenePath, 'utf8'))
         const draws = [
           ...(scene.floors ?? []),