Population invariance is a desirable property of test equating which might not hold when significant changes occur in the test population, such as those brought about by the COVID-19 pandemic. This research aims to investigate whether equating functions are reasonably invariant when the test population is impacted by the pandemic. Based on pseudo-test forms constructed from an operational form administered in the springs of 2019, 2020, and 2021, this study conducted preequating and postequating using different data collection designs and different sample sizes based on each year's data. Raw-to-scale score conversion tables from each equating and the group means after applying these conversions were compared with those from a criterion equating, that is, single group design postequating based on the 2019 data. Within each design and sample size condition, the magnitude of the differences between the 2021 equating and the criterion equating was mostly similar to the magnitude of differences between the 2020 equating and the criterion, indicating a reasonable extent of invariance in equating results. Nevertheless, some equating designs showed slightly less invariance than others.