Depending on the application, in some cases, the application starts returning HTTP errors in the response when the server load gets too high. For example, with too many concurrent requests, the application's database begins throwing connection timeout errors.
Usually, HTTP errors have an error response code, such as 500. In this case, StresStimulus will report this response as an error. However, in some instances, the response code is 200 (means a successful response), and the response body has some error text. In this case, StresStimulus will not be able to determine this response as an error, and therefore it is considered as a hidden error.
To expose these hidden errors, you can compare a replayed iteration with the recorded test case. There are two ways of doing that:
1. Open the VU Activity View (a) and right-click on the desired VU and Iteration (b) to investigate. Right-click and select Compare With Recorded (c).
2. Open the Waterfall chart (d) and select the desired VU (e) and Iteration (f) to investigate. Right-click and select Compare With Recorded (g).
In either case, a verification tree (h) that shows a comparison report between the recorded and replayed iteration will open. It is similar to verification.
If during the test, a session's content was purged, then it will be reported with image to signal unknown status.