  The Inspiral Merger Ringdown Consistency Test (IMRCT) is one among a battery
of tests of general relativity (GR) employed by the LIGO-Virgo-KAGRA (LVK)
collaboration. It is used to search for deviations from GR in detected
gravitational waves (GWs) from compact binary coalescences (CBCs) in a
model-agnostic way. The test compares source parameter estimates extracted
independently from the inspiral and post-inspiral portions of the CBC signals
and, therefore, crucially relies on the accurate modeling of the waveform.
Current implementations of the IMRCT routinely use quasicircular waveforms,
under the assumption that the residual eccentricity of the binary when the
emitted GWs enter the frequency band of the LVK detector network will be
negligible. In this work, we perform a detailed study to investigate the
typical magnitudes of this residual eccentricity that could potentially lead to
spurious violations of the IMRCT. To that end, we conduct injection campaigns
for a range of eccentricities and recover with both quasicircular and eccentric
waveforms. We find that an eccentric GW signal from a GW150914-like system with
$e_{\text{gw}} \gtrsim$ 0.04 at an orbit averaged frequency $\langle
f_{\text{ref}} \rangle=$ 25 Hz breaks the IMRCT if recovered with quasicircular
waveforms at $\gtrsim 68\%$ confidence. The violation becomes more severe
($\gtrsim 90\%$ confidence) for $e_{\text{gw}} =$ 0.055 at $\langle
f_{\text{ref}} \rangle=$ 25 Hz. On the other hand, when eccentric waveforms are
used, the IMRCT remains intact for all eccentricities considered. We also
briefly investigate the effect of the magnitude and orientation
(aligned/antialigned) of the component spins of the binary on the extent of the
spurious violations of the IMRCT. Our work, therefore, demonstrates the need
for accurate eccentric waveform models in the context of tests of GR.
