snapshot of https://github.com/TanStack/query.git (main, 2026-09-16; blobs > 131072B omitted)

packages/svelte-query/tests/utils.svelte.test.ts

@@ -0,0 +1,79 @@
+import { flushSync } from 'svelte'
+import { describe, expect, it, vi } from 'vitest'
+import { watchChanges } from '../src/utils.svelte.js'
+import { ref, withEffectRoot } from './utils.svelte.js'
+
+describe('watchChanges', () => {
+  it(
+    'should skip the first run and only call the effect on subsequent changes',
+    withEffectRoot(() => {
+      const source = ref(0)
+      const effect = vi.fn()
+
+      watchChanges(() => source.value, 'pre', effect)
+
+      // first run only records previousValues, effect is not called
+      flushSync()
+      expect(effect).not.toHaveBeenCalled()
+
+      source.value = 1
+      flushSync()
+      expect(effect).toHaveBeenCalledExactlyOnceWith(1, 0)
+    }),
+  )
+
+  it(
+    'should run with the "post" flush timing',
+    withEffectRoot(() => {
+      const source = ref(0)
+      const effect = vi.fn()
+
+      watchChanges(() => source.value, 'post', effect)
+
+      flushSync()
+      expect(effect).not.toHaveBeenCalled()
+
+      source.value = 1
+      flushSync()
+      expect(effect).toHaveBeenCalledExactlyOnceWith(1, 0)
+    }),
+  )
+
+  it(
+    'should track an array of sources and pass arrays of values',
+    withEffectRoot(() => {
+      const a = ref(1)
+      const b = ref(2)
+      const effect = vi.fn()
+
+      watchChanges([() => a.value, () => b.value], 'pre', effect)
+
+      flushSync()
+      expect(effect).not.toHaveBeenCalled()
+
+      a.value = 10
+      flushSync()
+      expect(effect).toHaveBeenCalledExactlyOnceWith([10, 2], [1, 2])
+    }),
+  )
+
+  it(
+    'should run the returned cleanup before the next effect run',
+    withEffectRoot(() => {
+      const source = ref(0)
+      const cleanup = vi.fn()
+      const effect = vi.fn(() => cleanup)
+
+      watchChanges(() => source.value, 'pre', effect)
+
+      flushSync()
+      source.value = 1
+      flushSync()
+      expect(cleanup).not.toHaveBeenCalled()
+
+      source.value = 2
+      flushSync()
+      expect(cleanup).toHaveBeenCalledOnce()
+    }),
+  )
+})