Test comparison is for comparing runs of the same test script
When using test comparison, you may only compare tests from the same series of test runs. You are not able to compare two different test scripts.
The test comparison feature built-in to k6 Cloud Results allows you to compare the results of two different test runs of the same test script. You can compare high-level metrics, individual checks and URL endpoints. You may wish to compare against a previous test run to look for a measurable difference in some change you made. Or you may be comparing against a known baseline.
Comparing results against a known baseline is a core part of the general methodology for automated performance testing. Baseline tests are important as they allow you to compare against a control to look for differences. Baseline tests should produce enough load to contain meaningful data and ideal results. In other words, a heavy stress test isn't a good baseline. Think much smaller.
In order to set your baseline, open up the results for the test run you wish to be your baseline. Select the three dots in the top right corner -> set as Baseline test run. Baseline tests are exempt from data retention policies.
To compare two test runs, open up one of the test runs. Then select the test run you want to compare it to using the select drop down on the right side of the test result page, just above the Performance Overview section.
After you select a test you will be brought into comparison mode. While in this mode you will see two charts in the Performance Overview section and you're able to change the base and target test you are comparing. This allows you to quickly change between different test runs and visually see if there are any obvious performance differences.
In the Thresholds tab, additional data is added to the table for the base and target test run. These columns will show the current vs compared test run's Threshold value for each Threshold and the pass/fail status. Clicking on any threshold will display a separate threshold chart for each test run.
In the Checks tab, additional data is added to the table for the base and target test run. These columns will show the difference in Success Rate, Success Count and Fail Count between the current and compared test runs. Clicking on any check will display separate checks charts for each test run.
In the HTTP tab, additional data is added to the table for the base and target test run. Here you can compare Count, p95, and p99 metrics for individual HTTP requests.
Clicking on a row will also show two separate charts, one for each test run. You can also change aggregation of the data to add additional metrics, such as timing breakdown for each HTTP request.