test: add a failing test to see the panic

Signed-off-by: Manan Gupta <[email protected]>

go/vt/vttablet/tabletserver/state_manager_test.go

@@ -701,6 +701,29 @@ func TestRefreshReplHealthLocked(t *testing.T) {
 	assert.False(t, sm.replHealthy)
 }
 
+func TestPanicInWait(t *testing.T) {
+	sm := newTestStateManager(t)
+	sm.wantState = StateServing
+	sm.state = StateServing
+	sm.replHealthy = true
+	ctx := context.Background()
+	// Simulate an Execute RPC running
+	err := sm.StartRequest(ctx, sm.target, false)
+	require.NoError(t, err)
+	go func() {
+		time.Sleep(100 * time.Millisecond)
+		// Simulate the previous RPC finishing after some delay
+		sm.EndRequest()
+		// Simulate a COMMIT call arriving right afterwards
+		err = sm.StartRequest(ctx, sm.target, true)
+		require.NoError(t, err)
+	}()
+
+	// Simulate going to a not serving state and calling unserveCommon that waits on requests.
+	sm.wantState = StateNotServing
+	sm.requests.Wait()
+}
+
 func verifySubcomponent(t *testing.T, order int64, component any, state testState) {
 	tos := component.(orderState)
 	assert.Equal(t, order, tos.Order())