test(splitAtom): moving first item to the end (#2238)

When the `before` is unspecified for the first item, it is being moved to the end of the list.

Co-authored-by: Daishi Kato <[email protected]>

tests/react/vanilla-utils/splitAtom.test.tsx

@@ -288,7 +288,12 @@ it('moving atoms', async () => {
           <TaskItem
             key={`${anAtom}`}
             onMoveLeft={() => {
-              if (index > 0) {
+              if (index === 0) {
+                dispatch({
+                  type: 'move',
+                  atom: anAtom,
+                })
+              } else if (index > 0) {
                 dispatch({
                   type: 'move',
                   atom: anAtom,
@@ -372,6 +377,13 @@ it('moving atoms', async () => {
       'help nana<>get dragon food<>get cat food<>'
     )
   })
+
+  fireEvent.click(getByTestId('help nana-leftbutton'))
+  await waitFor(() => {
+    expect(queryByTestId('list')?.textContent).toBe(
+      'get dragon food<>get cat food<>help nana<>'
+    )
+  })
 })
 
 it('read-only array atom', async () => {