doc: Add basic shell test description

Signed-off-by: Cyril Hrubis <[email protected]>
Reviewed-by: Avinesh Kumar <[email protected]>
Reviewed-by: Petr Vorel <[email protected]>

Author: metan-ucw

doc/conf.py

@@ -34,6 +34,7 @@
 extlinks = {
     'repo': (f'{ltp_repo}/%s', '%s'),
     'master': (f'{ltp_repo}/blob/master/%s', '%s'),
+    'shell_lib': (f'{ltp_repo}/blob/master/testcases/lib/%s', '%s'),
     'git_man': ('https://git-scm.com/docs/git-%s', 'git %s'),
     'man2': ('https://man7.org/linux/man-pages/man2/%s.2.html', '%s(2)'),
     'man3': ('https://man7.org/linux/man-pages/man3/%s.3.html', '%s(3)'),

doc/developers/api_shell_tests.rst

@@ -2,3 +2,94 @@
 
 LTP shell API
 =============
+
+Shell API overview
+------------------
+
+First lines of the shell test should be a shebang, a license, and copyrights.
+
+.. code-block:: shell
+
+   #!/bin/sh
+   # SPDX-License-Identifier: GPL-2.0-or-later
+   # Copyright 2099 Foo Bar <[email protected]>
+
+A documentation comment block formatted in ReStructuredText should follow right
+after these lines. This comment is parsed and exported into the LTP
+documentation at https://linux-test-project.readthedocs.io/en/latest/users/test_catalog.html
+
+.. code-block:: shell
+
+   # ---
+   # doc
+   # Test for a foo bar.
+   #
+   # This test is testing foo by checking that bar is doing xyz.
+   # ---
+
+The shell loader test library uses the :doc:`../developers/api_c_tests`
+internally by parsing a special JSON formatted comment and
+initializing it accordingly. The JSON format is nearly 1:1 serialization of the
+:ref:`struct tst_test` into a JSON. The environment must be always preset even
+when it's empty.
+
+.. code-block:: shell
+
+   # ---
+   # env
+   # {
+   #  "needs_root": true,
+   #  "needs_tmpdir": true,
+   #  "needs_kconfigs": ["CONFIG_NUMA=y"],
+   #  "tags": {
+   #   ["linux-git", "432fd03240fa"]
+   #  }
+   # }
+
+After the documentation and environment has been laid out we finally import the
+:shell_lib:`tst_loader.sh`. This will, among other things, start the
+:shell_lib:`tst_run_shell.c` binary, that will parse the shell test environment
+comment and initialize the C test library accordingly.
+
+.. code-block:: shell
+
+   . tst_loader.sh
+
+At this point everything has been set up and we can finally write the test
+function. The test results are reported by the usual functions :ref:`tst_res` and
+:ref:`tst_brk`. As in the C API these functions store results into a piece of shared
+memory as soon as they return so there is no need to propagate results event
+from child processes.
+
+.. code-block:: shell
+
+   tst_test()
+   {
+        tst_res TPASS "Bar enabled Foo"
+   }
+
+In order for the test to be actually executed the very last line of the script
+must source the :shell_lib:`tst_run.sh` script.
+
+.. code-block:: shell
+
+   . tst_run.sh
+
+In order to run a test from a LTP tree a few directories has to be added to the
+`$PATH`. Note that the number of `../` may depend on the depth of the current
+directory relative to the LTP root.
+
+.. code-block:: shell
+
+   $ PATH=$PATH:$PWD:$PWD/../../lib/ ./foo01.sh
+
+Test setup and cleanup
+----------------------
+
+The test setup and cleanup functions are optional and passed via variables.
+Similarly to the C API the setup is executed exactly once at the start of the
+test and the test cleanup is executed at the test end or when test was
+interrupted by :ref:`tst_brk`.
+
+   .. literalinclude:: ../../testcases/lib/tests/shell_loader_setup_cleanup.sh
+      :language: shell