Hyperons are produced with a nonzero spin polarization in $e^+e^-$ collisions, which can be straightforwardly parameterized in processes involving virtual photons or vector mesons, enabling direct and precise CP violation tests. These CP tests can be performed via decays such as $J/\psi,\psi'\to\Lambda\bar{\Lambda}$, $\Xi\bar{\Xi}$, and $\Sigma\bar{\Sigma}$. For cascade hyperon decays, exclusive measurements of the final-state particles allow for three independent CP-symmetry tests and the determination of strong and weak phase differences. The world’s largest data samples collected at the BESIII experiment at the $J/\psi$ and $\psi'$ has allowed for multi-dimensional analyses leveraging polarization and entanglement for these processes.