kconfig: tests: add a test for randconfig with dependent choices

Since commit 3b9a19e089 ("kconfig: loop as long as we changed some
symbols in randconfig"), conf_set_all_new_symbols() is repeated until
there is no more choice left to be shuffled. The motivation was to
shuffle a choice nested in another choice.

Although commit 09d5873e4d ("kconfig: allow only 'config', 'comment',
and 'if' inside 'choice'") disallowed the nested choice structure,
we must still keep 3b9a19e089 because there are still cases where
conf_set_all_new_symbols() must iterate.

scripts/kconfig/tests/choice_randomize/Kconfig is the test case.
The second choice depends on 'B', which is the member of the first
choice.

With 3b9a19e089 reverted, we would never get the pattern specified by
scripts/kconfig/tests/choice_randomize/expected_config2.

A real example can be found in lib/Kconfig.debug. Without 3b9a19e089,
the randconfig would not shuffle the "Compressed Debug information"
choice, which depends on DEBUG_INFO, which is derived from another
choice "Debug information".

My goal is to refactor Kconfig so that randconfig will work more
simply, without using the loop.

For now, let's add a test case to ensure all dependent choices are
shuffled, as it is a somewhat tricky case for the current Kconfig.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/tests/choice_randomize/__init__.py

@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: GPL-2.0-only
+"""
+Randomize all dependent choices
+
+This is a somewhat tricky case for randconfig; the visibility of one choice is
+determined by a member of another choice. Randconfig should be able to generate
+all possible patterns.
+"""
+
+
+def test(conf):
+
+    expected0 = False
+    expected1 = False
+    expected2 = False
+
+    for i in range(100):
+        assert conf.randconfig(seed=i) == 0
+
+        if conf.config_matches('expected_config0'):
+            expected0 = True
+        elif conf.config_matches('expected_config1'):
+            expected1 = True
+        elif conf.config_matches('expected_config2'):
+            expected2 = True
+        else:
+            assert False
+
+        if expected0 and expected1 and expected2:
+            break
+
+    assert expected0
+    assert expected1
+    assert expected2