testers.testBuildFailure': output is created so long as checks succeed

doc/build-helpers/testers.chapter.md

@@ -260,10 +260,14 @@ runCommand "example" {
 This tester wraps the functionality provided by [`testers.testBuildFailure`](#tester-testBuildFailure) to make writing checks easier by simplifying checking the exit code of the builder and asserting the existence of entries in the builder's log.
 Additionally, users may specify a script containing additional checks, accessing the result of applying `testers.testBuildFailure` through the variable `failed`.
 
+NOTE: This tester will produce an empty output and exit with success if none of the checks fail; there is no need to `touch "$out"` in `script`.
+
 :::{.example #ex-testBuildFailurePrime-doc-example}
 
 # Check that a build fails, and verify the changes made during build
 
+Re-using the example from [`testers.testBuildFailure`](#ex-testBuildFailure-showingenvironmentchanges), we can see how common checks are made easier and remove the need for `runCommand`:
+
 ```nix
 testers.testBuildFailure' {
   drv = runCommand "doc-example" { } ''
@@ -275,7 +279,6 @@ testers.testBuildFailure' {
   expectedBuilderLogEntries = [ "failing though" ];
   script = ''
     grep --silent -F 'ok-ish' "$failed/result"
-    touch "$out"
   '';
 }
 ```

pkgs/build-support/testers/test/default.nix

@@ -234,7 +234,6 @@ lib.recurseIntoAttrs {
       expectedBuilderLogEntries = [ "failing though" ];
       script = ''
         grep --silent -F 'ok-ish' "$failed/result"
-        touch "$out"
       '';
     };
 
@@ -258,7 +257,6 @@ lib.recurseIntoAttrs {
       ];
       script = ''
         grep --silent -F 'ok-ish' "$failed/result"
-        touch "$out"
       '';
     };
 
@@ -293,7 +291,6 @@ lib.recurseIntoAttrs {
         # Checking our note that dev is the default output
         echo $failed/_ | grep -- '-dev/_' >/dev/null
         echo 'All good.'
-        touch $out
       '';
     };
 
@@ -326,8 +323,6 @@ lib.recurseIntoAttrs {
       ];
       script = ''
         [[ ! -e side-effect ]]
-
-        touch $out
       '';
     };