The actual efficiency claim (which is also likely incorrect) is inverted from the original article, "We examined the conversion rates of approximately 2,300 individual test cases spread out within 338 files. Among these, approximately 500 test cases were successfully converted, executed, and passed. This highlights how effective AI can be, leading to a significant saving of 22% of developer time."
Reading that leads me to believe that 22% of the conversions succeeded and someone at Slack is making up numbers about developer time.
Reading that leads me to believe that 22% of the conversions succeeded and someone at Slack is making up numbers about developer time.