[PATCH v3 2/3] list: test: Add a test for list_is_head()

[David Gow]

list_is_head() was added recently[1], and didn't have a KUnit test. The
implementation is trivial, so it's not a particularly exciting test, but
it'd be nice to get back to full coverage of the list functions.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/linux/list.h?id=0425473037db40d9e322631f2d4dc6ef51f97e88

Signed-off-by: David Gow <davidgow@xxxxxxxxxx>
Acked-by: Daniel Latypov <dlatypov@xxxxxxxxxx>
Acked-by: Brendan Higgins <brendanhiggins@xxxxxxxxxx>
---

Changes since v2:
https://lore.kernel.org/linux-kselftest/20220208040122.695258-2-davidgow@xxxxxxxxxx/
- Use the _MSG variants of the assert macros, as suggested by Daniel
  Latypov.
Changes since v1:
https://lore.kernel.org/linux-kselftest/20220205061539.273330-2-davidgow@xxxxxxxxxx/
- Test both non-head elements of the same list and head elements of
  different lists.

---
 lib/list-test.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/lib/list-test.c b/lib/list-test.c
index f82a3c7788b8..19f13059439b 100644
--- a/lib/list-test.c
+++ b/lib/list-test.c
@@ -253,6 +253,24 @@ static void list_test_list_bulk_move_tail(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, i, 2);
 }
 
+static void list_test_list_is_head(struct kunit *test)
+{
+	struct list_head a, b, c;
+
+	/* Two lists: [a] -> b, [c] */
+	INIT_LIST_HEAD(&a);
+	INIT_LIST_HEAD(&c);
+	list_add_tail(&b, &a);
+
+	KUNIT_EXPECT_TRUE_MSG(test, list_is_head(&a, &a),
+		"Head element of same list");
+	KUNIT_EXPECT_FALSE_MSG(test, list_is_head(&a, &b),
+		"Non-head element of same list");
+	KUNIT_EXPECT_FALSE_MSG(test, list_is_head(&a, &c),
+		"Head element of different list");
+}
+
+
 static void list_test_list_is_first(struct kunit *test)
 {
 	struct list_head a, b;
@@ -730,6 +748,7 @@ static struct kunit_case list_test_cases[] = {
 	KUNIT_CASE(list_test_list_move),
 	KUNIT_CASE(list_test_list_move_tail),
 	KUNIT_CASE(list_test_list_bulk_move_tail),
+	KUNIT_CASE(list_test_list_is_head),
 	KUNIT_CASE(list_test_list_is_first),
 	KUNIT_CASE(list_test_list_is_last),
 	KUNIT_CASE(list_test_list_empty),
-- 
2.35.0.263.gb82422642f-goog