test: add POST body cache key update test case

Author: MattCCC

test/react/integration/hook.spec.tsx

@@ -1662,4 +1662,80 @@ describe('React Integration Tests', () => {
       global.localStorage = originalLocalStorage;
     });
   });
+
+  describe('POST body cache key update', () => {
+    it('should regenerate cache key and use updated body when POST body changes and refetch is called', async () => {
+      const testUrl = '/api/post-body-cache-key';
+      const initialBody = { value: 'first' };
+      const updatedBody = { value: 'second' };
+      let currentBody = initialBody;
+
+      // Mock fetch to echo back the request body
+      global.fetch = jest.fn().mockImplementation((_url, config) => {
+        const parsedBody =
+          config && config.body ? JSON.parse(config.body) : undefined;
+        return Promise.resolve({
+          ok: true,
+          status: 200,
+          data: parsedBody,
+          body: parsedBody,
+          json: () => Promise.resolve(parsedBody),
+        });
+      });
+
+      // React state simulation
+      let setBody: (b: typeof initialBody) => void = () => {};
+      function BodyComponent() {
+        const [body, _setBody] = React.useState(currentBody);
+        setBody = _setBody;
+        const { data, refetch, isLoading } = useFetcher(testUrl, {
+          method: 'POST',
+          body,
+        });
+        return (
+          <div>
+            <div data-testid="data">
+              {data ? JSON.stringify(data) : 'No Data'}
+            </div>
+            <div data-testid="loading">
+              {isLoading ? 'Loading...' : 'Not Loading'}
+            </div>
+            <button data-testid="refetch-btn" onClick={() => refetch(true)}>
+              Refetch
+            </button>
+          </div>
+        );
+      }
+
+      render(<BodyComponent />);
+
+      // Wait for initial fetch
+      await waitFor(() => {
+        expect(screen.getByTestId('data')).toHaveTextContent('No Data');
+      });
+
+      // Act: update the body asynchronously
+      act(() => {
+        currentBody = updatedBody;
+        setBody(updatedBody);
+      });
+
+      // Refetch with new body
+      fireEvent.click(screen.getByTestId('refetch-btn'));
+
+      // Assert: data should match updated body
+      await waitFor(() => {
+        expect(screen.getByTestId('data')).toHaveTextContent('second');
+      });
+
+      // Also check that fetch was called with the updated body
+      expect(global.fetch).toHaveBeenLastCalledWith(
+        testUrl,
+        expect.objectContaining({
+          method: 'POST',
+          body: JSON.stringify(updatedBody),
+        }),
+      );
+    });
+  });
 });