  A highly granular electromagnetic calorimeter with scintillator strip readout
is being developed for future lepton collider experiments. A prototype of 21.5
$X_0$ depth and $180 \times 180 $mm$^2$ transverse dimensions was constructed,
consisting of 2160 individually read out $10 \times 45 \times 3$ mm$^3$
scintillator strips. This prototype was tested using electrons of 2--32 GeV at
the Fermilab Test Beam Facility in 2009. Deviations from linear energy response
were less than 1.1\%, and the intrinsic energy resolution was determined to be
$(12.5 \pm 0.1 (\mathrm{stat.}) \pm0.4
(\mathrm{syst.}))\%/\sqrt{E[\mathrm{GeV}]}\oplus (1.2 \pm
0.1(\mathrm{stat.})^{+0.6}_{-0.7}(\mathrm{syst.}))\%$, where the uncertainties
correspond to statistical and systematic sources, respectively.
