[PATCH v3] Documentation: KUnit: Update the instructions on how to test static functions

[Arthur Grillo]

Now that we have the VISIBLE_IF_KUNIT and EXPORT_SYMBOL_IF_KUNIT macros,
update the instructions to recommend this way of testing static
functions.

Signed-off-by: Arthur Grillo <arthurgrillo@xxxxxxxxxx>
---
Changes in v3:
- Maintain the old '#include' way
- Link to v2: https://lore.kernel.org/r/20240108-kunit-doc-export-v2-1-8f2dd3395fed@xxxxxxxxxx

Changes in v2:
- Fix #if condition
- Link to v1: https://lore.kernel.org/r/20240108-kunit-doc-export-v1-1-119368df0d96@xxxxxxxxxx
---
 Documentation/dev-tools/kunit/usage.rst | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
index c27e1646ecd9..8e35b94a17ec 100644
--- a/Documentation/dev-tools/kunit/usage.rst
+++ b/Documentation/dev-tools/kunit/usage.rst
@@ -671,8 +671,23 @@ Testing Static Functions
 ------------------------
 
 If we do not want to expose functions or variables for testing, one option is to
-conditionally ``#include`` the test file at the end of your .c file. For
-example:
+conditionally export the used symbol. For example:
+
+.. code-block:: c
+
+	/* In my_file.c */
+
+	VISIBLE_IF_KUNIT int do_interesting_thing();
+	EXPORT_SYMBOL_IF_KUNIT(do_interesting_thing);
+
+	/* In my_file.h */
+
+	#if IS_ENABLED(CONFIG_KUNIT)
+		int do_interesting_thing(void);
+	#endif
+
+Alternatively, you could conditionally ``#include`` the test file at the end of
+your .c file. For example:
 
 .. code-block:: c
 

---
base-commit: eeb8e8d9f124f279e80ae679f4ba6e822ce4f95f
change-id: 20240108-kunit-doc-export-eec1f910ab67

Best regards,
-- 
Arthur Grillo <arthurgrillo@xxxxxxxxxx>