[PATCH v3 3/3] selftests/user_events: Add test cases when event is diabled

[sunliming]

When user_events are disabled, it's write operation should return zero.
Add this test cases.

Signed-off-by: sunliming <sunliming@xxxxxxxxxx>
---
 tools/testing/selftests/user_events/ftrace_test.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/testing/selftests/user_events/ftrace_test.c b/tools/testing/selftests/user_events/ftrace_test.c
index d33bd31425db..7968d69c3a5c 100644
--- a/tools/testing/selftests/user_events/ftrace_test.c
+++ b/tools/testing/selftests/user_events/ftrace_test.c
@@ -297,6 +297,9 @@ TEST_F(user, write_events) {
 	io[0].iov_base = &reg.write_index;
 	io[0].iov_len = sizeof(reg.write_index);
 
+	/* Write should return zero when event is not enabled */
+	ASSERT_EQ(0, writev(self->data_fd, (const struct iovec *)io, 3));
+
 	/* Enable event */
 	self->enable_fd = open(enable_file, O_RDWR);
 	ASSERT_NE(-1, write(self->enable_fd, "1", sizeof("1")))
-- 
2.25.1