[PATCH v2 3/3] list: test: Add a test for list_entry_is_head()

[David Gow]

The list_entry_is_head() macro was added[1] after the list KUnit tests,
so wasn't tested. Add a new KUnit test to complete the set.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e130816164e244b692921de49771eeb28205152d

Signed-off-by: David Gow <davidgow@xxxxxxxxxx>
---

Changes since v1:
https://lore.kernel.org/linux-kselftest/20220205061539.273330-3-davidgow@xxxxxxxxxx/
- Rework the test entirely to better match the improved list_is_head()
  test.

---
 lib/list-test.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/lib/list-test.c b/lib/list-test.c
index 1960615d1a9f..80dd14c4ca1f 100644
--- a/lib/list-test.c
+++ b/lib/list-test.c
@@ -546,6 +546,22 @@ static void list_test_list_entry(struct kunit *test)
 				struct list_test_struct, list));
 }
 
+static void list_test_list_entry_is_head(struct kunit *test)
+{
+	struct list_test_struct test_struct1, test_struct2, test_struct3;
+
+	INIT_LIST_HEAD(&test_struct1.list);
+	INIT_LIST_HEAD(&test_struct3.list);
+
+	list_add_tail(&test_struct2.list, &test_struct1.list);
+
+	KUNIT_EXPECT_TRUE(test, list_entry_is_head((&test_struct1), &test_struct1.list, list));
+	/* Non-head element of same list */
+	KUNIT_EXPECT_FALSE(test, list_entry_is_head((&test_struct2), &test_struct1.list, list));
+	/* Head element of different list */
+	KUNIT_EXPECT_FALSE(test, list_entry_is_head((&test_struct3), &test_struct1.list, list));
+}
+
 static void list_test_list_first_entry(struct kunit *test)
 {
 	struct list_test_struct test_struct1, test_struct2;
@@ -761,6 +777,7 @@ static struct kunit_case list_test_cases[] = {
 	KUNIT_CASE(list_test_list_splice_init),
 	KUNIT_CASE(list_test_list_splice_tail_init),
 	KUNIT_CASE(list_test_list_entry),
+	KUNIT_CASE(list_test_list_entry_is_head),
 	KUNIT_CASE(list_test_list_first_entry),
 	KUNIT_CASE(list_test_list_last_entry),
 	KUNIT_CASE(list_test_list_first_entry_or_null),
-- 
2.35.0.263.gb82422642f-goog