kunit: test: add KUnit test runner core

Add core facilities for defining unit tests; this provides a common way
to define test cases, functions that execute code which is under test
and determine whether the code under test behaves as expected; this also
provides a way to group together related test cases in test suites (here
we call them test_modules).

Just define test cases and how to execute them for now; setting
expectations on code will be defined later.
Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

include/kunit/test.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Base unit test (KUnit) API.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#ifndef _KUNIT_TEST_H
+#define _KUNIT_TEST_H
+
+#include <linux/types.h>
+
+struct kunit;
+
+/**
+ * struct kunit_case - represents an individual test case.
+ *
+ * @run_case: the function representing the actual test case.
+ * @name:     the name of the test case.
+ *
+ * A test case is a function with the signature,
+ * ``void (*)(struct kunit *)`` that makes expectations (see
+ * KUNIT_EXPECT_TRUE()) about code under test. Each test case is associated
+ * with a &struct kunit_suite and will be run after the suite's init
+ * function and followed by the suite's exit function.
+ *
+ * A test case should be static and should only be created with the
+ * KUNIT_CASE() macro; additionally, every array of test cases should be
+ * terminated with an empty test case.
+ *
+ * Example:
+ *
+ * .. code-block:: c
+ *
+ *	void add_test_basic(struct kunit *test)
+ *	{
+ *		KUNIT_EXPECT_EQ(test, 1, add(1, 0));
+ *		KUNIT_EXPECT_EQ(test, 2, add(1, 1));
+ *		KUNIT_EXPECT_EQ(test, 0, add(-1, 1));
+ *		KUNIT_EXPECT_EQ(test, INT_MAX, add(0, INT_MAX));
+ *		KUNIT_EXPECT_EQ(test, -1, add(INT_MAX, INT_MIN));
+ *	}
+ *
+ *	static struct kunit_case example_test_cases[] = {
+ *		KUNIT_CASE(add_test_basic),
+ *		{}
+ *	};
+ *
+ */
+struct kunit_case {
+	void (*run_case)(struct kunit *test);
+	const char *name;
+
+	/* private: internal use only. */
+	bool success;
+};
+
+/**
+ * KUNIT_CASE - A helper for creating a &struct kunit_case
+ *
+ * @test_name: a reference to a test case function.
+ *
+ * Takes a symbol for a function representing a test case and creates a
+ * &struct kunit_case object from it. See the documentation for
+ * &struct kunit_case for an example on how to use it.
+ */
+#define KUNIT_CASE(test_name) { .run_case = test_name, .name = #test_name }
+
+/**
+ * struct kunit_suite - describes a related collection of &struct kunit_case
+ *
+ * @name:	the name of the test. Purely informational.
+ * @init:	called before every test case.
+ * @exit:	called after every test case.
+ * @test_cases:	a null terminated array of test cases.
+ *
+ * A kunit_suite is a collection of related &struct kunit_case s, such that
+ * @init is called before every test case and @exit is called after every
+ * test case, similar to the notion of a *test fixture* or a *test class*
+ * in other unit testing frameworks like JUnit or Googletest.
+ *
+ * Every &struct kunit_case must be associated with a kunit_suite for KUnit
+ * to run it.
+ */
+struct kunit_suite {
+	const char name[256];
+	int (*init)(struct kunit *test);
+	void (*exit)(struct kunit *test);
+	struct kunit_case *test_cases;
+};
+
+/**
+ * struct kunit - represents a running instance of a test.
+ *
+ * @priv: for user to store arbitrary data. Commonly used to pass data
+ *	  created in the init function (see &struct kunit_suite).
+ *
+ * Used to store information about the current context under which the test
+ * is running. Most of this data is private and should only be accessed
+ * indirectly via public functions; the one exception is @priv which can be
+ * used by the test writer to store arbitrary data.
+ */
+struct kunit {
+	void *priv;
+
+	/* private: internal use only. */
+	const char *name; /* Read only after initialization! */
+	/*
+	 * success starts as true, and may only be set to false during a
+	 * test case; thus, it is safe to update this across multiple
+	 * threads using WRITE_ONCE; however, as a consequence, it may only
+	 * be read after the test case finishes once all threads associated
+	 * with the test case have terminated.
+	 */
+	bool success; /* Read only after test_case finishes! */
+};
+
+void kunit_init_test(struct kunit *test, const char *name);
+
+int kunit_run_tests(struct kunit_suite *suite);
+
+/**
+ * kunit_test_suite() - used to register a &struct kunit_suite with KUnit.
+ *
+ * @suite: a statically allocated &struct kunit_suite.
+ *
+ * Registers @suite with the test framework. See &struct kunit_suite for
+ * more information.
+ *
+ * NOTE: Currently KUnit tests are all run as late_initcalls; this means
+ * that they cannot test anything where tests must run at a different init
+ * phase. One significant restriction resulting from this is that KUnit
+ * cannot reliably test anything that is initialize in the late_init phase;
+ * another is that KUnit is useless to test things that need to be run in
+ * an earlier init phase.
+ *
+ * TODO(brendanhiggins@google.com): Don't run all KUnit tests as
+ * late_initcalls.  I have some future work planned to dispatch all KUnit
+ * tests from the same place, and at the very least to do so after
+ * everything else is definitely initialized.
+ */
+#define kunit_test_suite(suite)						       \
+	static int kunit_suite_init##suite(void)			       \
+	{								       \
+		return kunit_run_tests(&suite);				       \
+	}								       \
+	late_initcall(kunit_suite_init##suite)
+
+void __printf(3, 4) kunit_printk(const char *level,
+				 const struct kunit *test,
+				 const char *fmt, ...);
+
+/**
+ * kunit_info() - Prints an INFO level message associated with @test.
+ *
+ * @test: The test context object.
+ * @fmt:  A printk() style format string.
+ *
+ * Prints an info level message associated with the test suite being run.
+ * Takes a variable number of format parameters just like printk().
+ */
+#define kunit_info(test, fmt, ...) \
+	kunit_printk(KERN_INFO, test, fmt, ##__VA_ARGS__)
+
+/**
+ * kunit_warn() - Prints a WARN level message associated with @test.
+ *
+ * @test: The test context object.
+ * @fmt:  A printk() style format string.
+ *
+ * Prints a warning level message.
+ */
+#define kunit_warn(test, fmt, ...) \
+	kunit_printk(KERN_WARNING, test, fmt, ##__VA_ARGS__)
+
+/**
+ * kunit_err() - Prints an ERROR level message associated with @test.
+ *
+ * @test: The test context object.
+ * @fmt:  A printk() style format string.
+ *
+ * Prints an error level message.
+ */
+#define kunit_err(test, fmt, ...) \
+	kunit_printk(KERN_ERR, test, fmt, ##__VA_ARGS__)
+
+#endif /* _KUNIT_TEST_H */

lib/kunit/Kconfig

+#
+# KUnit base configuration
+#
+
+menuconfig KUNIT
+	bool "KUnit - Enable support for unit tests"
+	help
+	  Enables support for kernel unit tests (KUnit), a lightweight unit
+	  testing and mocking framework for the Linux kernel. These tests are
+	  able to be run locally on a developer's workstation without a VM or
+	  special hardware when using UML. Can also be used on most other
+	  architectures. For more information, please see
+	  Documentation/dev-tools/kunit/.

lib/kunit/Makefile

+obj-$(CONFIG_KUNIT) +=			test.o

lib/kunit/test.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Base unit test (KUnit) API.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#include <kunit/test.h>
+#include <linux/kernel.h>
+
+static void kunit_set_failure(struct kunit *test)
+{
+	WRITE_ONCE(test->success, false);
+}
+
+static int kunit_vprintk_emit(int level, const char *fmt, va_list args)
+{
+	return vprintk_emit(0, level, NULL, 0, fmt, args);
+}
+
+static int kunit_printk_emit(int level, const char *fmt, ...)
+{
+	va_list args;
+	int ret;
+
+	va_start(args, fmt);
+	ret = kunit_vprintk_emit(level, fmt, args);
+	va_end(args);
+
+	return ret;
+}
+
+static void kunit_vprintk(const struct kunit *test,
+			  const char *level,
+			  struct va_format *vaf)
+{
+	kunit_printk_emit(level[1] - '0', "\t# %s: %pV", test->name, vaf);
+}
+
+static void kunit_print_tap_version(void)
+{
+	static bool kunit_has_printed_tap_version;
+
+	if (!kunit_has_printed_tap_version) {
+		kunit_printk_emit(LOGLEVEL_INFO, "TAP version 14\n");
+		kunit_has_printed_tap_version = true;
+	}
+}
+
+static size_t kunit_test_cases_len(struct kunit_case *test_cases)
+{
+	struct kunit_case *test_case;
+	size_t len = 0;
+
+	for (test_case = test_cases; test_case->run_case; test_case++)
+		len++;
+
+	return len;
+}
+
+static void kunit_print_subtest_start(struct kunit_suite *suite)
+{
+	kunit_print_tap_version();
+	kunit_printk_emit(LOGLEVEL_INFO, "\t# Subtest: %s\n", suite->name);
+	kunit_printk_emit(LOGLEVEL_INFO,
+			  "\t1..%zd\n",
+			  kunit_test_cases_len(suite->test_cases));
+}
+
+static void kunit_print_ok_not_ok(bool should_indent,
+				  bool is_ok,
+				  size_t test_number,
+				  const char *description)
+{
+	const char *indent, *ok_not_ok;
+
+	if (should_indent)
+		indent = "\t";
+	else
+		indent = "";
+
+	if (is_ok)
+		ok_not_ok = "ok";
+	else
+		ok_not_ok = "not ok";
+
+	kunit_printk_emit(LOGLEVEL_INFO,
+			  "%s%s %zd - %s\n",
+			  indent, ok_not_ok, test_number, description);
+}
+
+static bool kunit_suite_has_succeeded(struct kunit_suite *suite)
+{
+	const struct kunit_case *test_case;
+
+	for (test_case = suite->test_cases; test_case->run_case; test_case++)
+		if (!test_case->success)
+			return false;
+
+	return true;
+}
+
+static void kunit_print_subtest_end(struct kunit_suite *suite)
+{
+	static size_t kunit_suite_counter = 1;
+
+	kunit_print_ok_not_ok(false,
+			      kunit_suite_has_succeeded(suite),
+			      kunit_suite_counter++,
+			      suite->name);
+}
+
+static void kunit_print_test_case_ok_not_ok(struct kunit_case *test_case,
+					    size_t test_number)
+{
+	kunit_print_ok_not_ok(true,
+			      test_case->success,
+			      test_number,
+			      test_case->name);
+}
+
+void kunit_init_test(struct kunit *test, const char *name)
+{
+	test->name = name;
+	test->success = true;
+}
+
+/*
+ * Performs all logic to run a test case.
+ */
+static void kunit_run_case(struct kunit_suite *suite,
+			   struct kunit_case *test_case)
+{
+	struct kunit test;
+
+	kunit_init_test(&test, test_case->name);
+
+	if (suite->init) {
+		int ret;
+
+		ret = suite->init(&test);
+		if (ret) {
+			kunit_err(&test, "failed to initialize: %d\n", ret);
+			kunit_set_failure(&test);
+			test_case->success = test.success;
+			return;
+		}
+	}
+
+	test_case->run_case(&test);
+
+	if (suite->exit)
+		suite->exit(&test);
+
+	test_case->success = test.success;
+}
+
+int kunit_run_tests(struct kunit_suite *suite)
+{
+	struct kunit_case *test_case;
+	size_t test_case_count = 1;
+
+	kunit_print_subtest_start(suite);
+
+	for (test_case = suite->test_cases; test_case->run_case; test_case++) {
+		kunit_run_case(suite, test_case);
+		kunit_print_test_case_ok_not_ok(test_case, test_case_count++);
+	}
+
+	kunit_print_subtest_end(suite);
+
+	return 0;
+}
+
+void kunit_printk(const char *level,
+		  const struct kunit *test,
+		  const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, fmt);
+
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	kunit_vprintk(test, level, &vaf);
+
+	va_end(args);
+}