  Neutrino oscillation experiments have measured precisely the mass-squared
differences of three neutrino mass eigenstates, and three leptonic mixing
angles by utilizing both neutrino and anti-neutrino oscillations. The possible
CPT violation may manifest itself in the difference of neutrino and
anti-neutrino oscillation parameters, making these experiments promising tools
for testing CPT invariance. We investigate empirically the sensitivity of the
CPT test via the difference in mass-squared splittings ($\Delta m^2_{31} -
\Delta \overline{m}^2_{31}$) and in leptonic mixing angles ($\sin^2\theta_{23}
- \sin^2\overline{\theta}_{23}$) with the synergy of T2K-II, NO$\nu$A
extension, and JUNO experiments. If the CPT symmetry is found to be conserved,
the joint analysis of the three experiments will be able to establish limits of
$|\Delta m^2_{31} - \Delta \overline{m}^2_{31}|$ < $5.3\times 10^{-3}
\text{eV}^2$ and $|\sin^2\theta_{23} - \sin^2\overline{\theta}_{23}|$ < $0.10$
at 3$\sigma$ C. L. on the possible CPT violation. We find that with ($\Delta
m^2_{31} - \Delta \overline{m}^2_{31}$), the dependence of the statistical
significance on the relevant parameters to exclude the CPT conservation is
marginal, and that, if the difference in the best-fit values of $\Delta
m^2_{31}$ and $\Delta \overline{m}^2_{31}$ measured by MINOS(+) and NO$\nu$A
persists as the true, the combined analysis will rule out the CPT conservation
at 4$\sigma$ C. L.. With the ($\sin^2\theta_{23} -
\sin^2\overline{\theta}_{23}$), the statistical significance to exclude CPT
invariance depends strongly on the true value of
$\theta_{23}(\overline{\theta}_{23})$. In case of maximal mixing of
$\theta_{23}$, the CPT conservation will be excluded at 3$\sigma$ C. L. or more
if the difference in the best-fit values of $\theta_{23}$ and
$\overline{\theta}_{23}$ remains as the true.
