If you use LogScale to monitor how your software is building, your build pipeline might already output the numbers you want, like the number of failed tests. Instead of calculating this number based on the failed tests that have been logged, you can display the number the system has given you:

commit = 67686a1
| /Tests failed: (?<tests_failed>\d+)/
| select(tests_failed)

Assuming there is only one build per commit, this search extracts the number of tests that failed in the build, and uses the select() function to remove extraneous fields from the row. Without calling select(), the row might contain multiple numeric fields, and the Single Value widget would not know what to display.