  In this work, we revisit existing oracle generation studies plus ChatGPT to
empirically investigate the current standing of their performance in both
NLG-based and test adequacy metrics. Specifically, we train and run four
state-of-the-art test oracle generation models on five NLG-based and two test
adequacy metrics for our analysis. We apply two different correlation analyses
between these two different sets of metrics. Surprisingly, we found no
significant correlation between the NLG-based metrics and test adequacy
metrics. For instance, oracles generated from ChatGPT on the project
activemq-artemis had the highest performance on all the NLG-based metrics among
the studied NOGs, however, it had the most number of projects with a decrease
in test adequacy metrics compared to all the studied NOGs. We further conduct a
qualitative analysis to explore the reasons behind our observations, we found
that oracles with high NLG-based metrics but low test adequacy metrics tend to
have complex or multiple chained method invocations within the oracle's
parameters, making it hard for the model to generate completely, affecting the
test adequacy metrics. On the other hand, oracles with low NLG-based metrics
but high test adequacy metrics tend to have to call different assertion types
or a different method that functions similarly to the ones in the ground truth.
Overall, this work complements prior studies on test oracle generation with an
extensive performance evaluation with both NLG and test adequacy metrics and
provides guidelines for better assessment of deep learning applications in
software test generation in the future.
