test: add regression test for getCanvasCenter null guard (#8399)

src/services/litegraphService.test.ts

@@ -0,0 +1,43 @@
+import { createTestingPinia } from '@pinia/testing'
+import { setActivePinia } from 'pinia'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+vi.mock('@/scripts/app', () => ({
+  app: { canvas: undefined },
+  ComfyApp: class {}
+}))
+
+import { app } from '@/scripts/app'
+import { useLitegraphService } from '@/services/litegraphService'
+
+describe('useLitegraphService().getCanvasCenter', () => {
+  beforeEach(() => {
+    setActivePinia(createTestingPinia({ stubActions: false }))
+  })
+
+  it('returns origin when canvas is not yet initialised', () => {
+    Reflect.set(app, 'canvas', undefined)
+
+    const center = useLitegraphService().getCanvasCenter()
+
+    expect(center).toEqual([0, 0])
+  })
+
+  it('returns origin when canvas exists but ds.visible_area is missing', () => {
+    Reflect.set(app, 'canvas', { ds: {} })
+
+    const center = useLitegraphService().getCanvasCenter()
+
+    expect(center).toEqual([0, 0])
+  })
+
+  it('returns the visible-area centre once the canvas is ready', () => {
+    Reflect.set(app, 'canvas', {
+      ds: { visible_area: [10, 20, 200, 100] }
+    })
+
+    const center = useLitegraphService().getCanvasCenter()
+
+    expect(center).toEqual([110, 70])
+  })
+})