test that Suspense mode calls queryFn only once (#325)

Co-authored-by: Simon Carpinter <simon.carpinter@charge.net.nz>

Author: simoncarpinter

src/tests/suspense.test.js

@@ -0,0 +1,33 @@
+import { render, waitForElement, cleanup } from '@testing-library/react'
+import * as React from 'react'
+
+import { useQuery, queryCache } from '../index'
+import { sleep } from './utils'
+
+describe("useQuery's in Suspense mode", () => {
+  afterEach(() => {
+    queryCache.clear()
+    cleanup()
+  })
+
+  it('should not call the queryFn twice when used in Suspense mode', async () => {
+    const queryFn = jest.fn()
+    queryFn.mockImplementation(() => sleep(10))
+
+    function Page() {
+      useQuery(['test'], queryFn, { suspense: true })
+
+      return 'rendered'
+    }
+
+    const rendered = render(
+      <React.Suspense fallback="loading">
+        <Page />
+      </React.Suspense>
+    )
+
+    await waitForElement(() => rendered.getByText('rendered'))
+
+    expect(queryFn).toHaveBeenCalledTimes(1)
+  })
+})