  Tests of lepton universality in $B^0\to K^0_S \ell^+ \ell^-$ and $B^+\to
K^{*+} \ell^+ \ell^-$ decays where $\ell$ is either an electron or a muon are
presented. The differential branching fractions of $B^0\to K^0_S e^+ e^-$ and
$B^+\to K^{*+} e^+ e^-$ decays are measured in intervals of the dilepton
invariant mass squared. The measurements are performed using proton-proton
collision data recorded by the LHCb experiment, corresponding to an integrated
luminosity of $9\, \mathrm{fb}^{-1}$. The results are consistent with the
Standard Model and previous tests of lepton universality in related decay
modes. The first observation of $B^0 \to K^0_S e^+ e^-$ and $B^+ \to K^{*+} e^+
e^-$ decays is reported.
