  We present a detailed comparison of optical H II region spectra to
photoionization models based on modern stellar atmosphere models. We examine
both spatially resolved and integrated emission-line spectra of the HII regions
DEM L323, DEM L243, DEM L199, and DEM L301 in the Large Magellanic Cloud. The
published spectral classifications of the dominant stars range from O7 to WN3,
and morphologies range from Stromgren sphere to shell structure. Two of the
objects include SNR contamination. The overall agreement with the predictions
is generally within 0.2 dex for major diagnostic line ratios. An apparent
pattern in the remaining discrepancies is that the predicted T_e is ~1000 K
hotter than observed. (Abridged)
  Our analysis of the complex DEM L199 allows a nebular emission-line test of
unprecedented detail for WR atmospheres. Surprisingly, we find no nebular He II
4686 emission, despite the fact that both of the dominant WN3 stars should be
hot enough to fully ionize He I in their atmospheres.
  We confirm that the \eta-prime emission-line parameter is not as useful as
hoped for determining the ionizing stellar effective temperature, T*. Both
empirically and theoretically, we find that it is insensitive for T* >40 kK,
and that it also varies spatially. The shock-contaminated objects show that
\eta-prime will also yield a spuriously high T* in the presence of shocks. It
is furthermore sensitive to shell morphology. We suggest [Ne III]/Hb as an
additional probe of T*. Although it is abundance-dependent, [Ne III]/Hb has
higher sensitivity to T*, is independent of morphology, and is insensitive to
shocks in our objects. We attempt a first empirical calibration of these
nebular diagnostics of T*.
