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[v2,1/6] t: document test_lazy_prereq

Message ID 20250311212505.2920181-2-gitster@pobox.com (mailing list archive)
State New
Headers show
Series drop "name-rev --stdin" support | expand

Commit Message

Junio C Hamano March 11, 2025, 9:25 p.m. UTC 
The t/README file talked about test_set_prereq but lacked
explanation on test_lazy_prereq, which is a more modern way to
define prerequisites.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 t/README | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)
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Patch

diff --git a/t/README b/t/README
index 53e5b4a710..3ce9f5a393 100644
--- a/t/README
+++ b/t/README
@@ -818,7 +818,7 @@  Skipping tests
 --------------
 
 If you need to skip tests you should do so by using the three-arg form
-of the test_* functions (see the "Test harness library" section
+of the test_expect_* functions (see the "Test harness library" section
 below), e.g.:
 
     test_expect_success PERL 'I need Perl' '
@@ -965,6 +965,27 @@  see test-lib-functions.sh for the full list and their options.
 	    test_done
 	fi
 
+ - test_lazy_prereq <prereq> <script>
+
+   Declare the way to determine if a test prerequisite <prereq> is
+   satisified or not, but delay the actual determination until the
+   prerequisite is actually used by "test_have_prereq" or the
+   three-arg form of the test_expect_* functions.  For example, this
+   is how the SYMLINKS prerequisite is declared to see if the platform
+   supports symbolic links:
+
+	test_lazy_prereq SYMLINKS '
+		ln -s x y && test -h y
+	'
+
+   The script is lazily invoked when SYMLINKS prerequisite is first
+   queried by either "test_have_prereq SYMLINKS" or "test_expect_*
+   SYMLINKS ...".  The script is run in a temporary directory inside
+   a subshell, so you do not have to worry about removing temporary
+   files you create there.  When the script exits with status 0, the
+   prerequisite is set.  Exiting with non-zero status makes the
+   prerequisite unsatisified.
+
  - test_expect_code <exit-code> <command>
 
    Run a command and ensure that it exits with the given exit code.