test(svelte-query/useMutationState): add type tests for default 'MutationState' and 'select' inference (#10504)

Author: sukvvon

packages/svelte-query/tests/useMutationState/useMutationState.test-d.ts

@@ -0,0 +1,24 @@
+import { describe, expectTypeOf, it } from 'vitest'
+import { useMutationState } from '../../src/index.js'
+import type { MutationState, MutationStatus } from '@tanstack/query-core'
+
+describe('useMutationState', () => {
+  it('should default to MutationState', () => {
+    const result = useMutationState({
+      filters: { status: 'pending' },
+    })
+
+    expectTypeOf(result).toEqualTypeOf<
+      Array<MutationState<unknown, Error, unknown, unknown>>
+    >()
+  })
+
+  it('should infer with select', () => {
+    const result = useMutationState({
+      filters: { status: 'pending' },
+      select: (mutation) => mutation.state.status,
+    })
+
+    expectTypeOf(result).toEqualTypeOf<Array<MutationStatus>>()
+  })
+})