doc: mention overriding SUBDIRS= with TESTS= and recursive make.

This change palliates https://bugs.gnu.org/42883,
though it's not a real fix.

* doc/automake.texi (Parallel Test Harness): with recursive
make, when limiting the tests run, also presumably needed to
override SUBDIRS.

diff --git a/doc/automake.texi b/doc/automake.texi
index 17bc2dae6e123893a66e2131ba100e4220177c7a..177bd66f9befc0df646adb7833b92e04927e92fc 100644 (file)
--- a/doc/automake.texi
+++ b/doc/automake.texi
@@ -9372,7 +9372,19 @@ command like this to run only a subset of the tests:
 env TESTS="foo.test bar.test" make -e check
 @end example
 
-Note however that the command above will unconditionally overwrite the
+@c https://bugs.gnu.org/42883
+If you're using a recursive make setup, you'll probably also need to
+override @code{SUBDIRS}:
+
+@example
+env TESTS="foo.test bar.test" make -e check SUBDIRS=
+@end example
+
+Otherwise, the test harness will descend into all subdirectories,
+where the tests presumably do not exist, and thus fail.  (Patch to
+provide better behavior would be welcome.)
+
+Another issue: the command above will unconditionally overwrite the
 @file{test-suite.log} file, thus clobbering the recorded results
 of any previous testsuite run.  This might be undesirable for packages
 whose testsuite takes a long time to execute.  Luckily, this problem can