kunit: string-stream: Add tests for freeing resource-managed string_stream

string_stream_managed_free_test() allocates a resource-managed
string_stream and tests that kunit_free_string_stream() calls
string_stream_destroy().

string_stream_resource_free_test() allocates a resource-managed
string_stream and tests that string_stream_destroy() is called
when the test resources are cleaned up.

The old string_stream_init_test() has been split into two tests,
one for kunit_alloc_string_stream() and the other for
alloc_string_stream().

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

lib/kunit/string-stream.c

@@ -6,6 +6,7 @@
  * Author: Brendan Higgins <brendanhiggins@google.com>
  */
 
+#include <kunit/static_stub.h>
 #include <kunit/test.h>
 #include <linux/list.h>
 #include <linux/slab.h>
@@ -170,6 +171,8 @@ struct string_stream *alloc_string_stream(gfp_t gfp)
 
 void string_stream_destroy(struct string_stream *stream)
 {
+	KUNIT_STATIC_STUB_REDIRECT(string_stream_destroy, stream);
+
 	if (!stream)
 		return;