[PATCH v6 01/18] kunit: test: add KUnit test runner core

[Brendan Higgins]

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@xxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
Changes Since Last Revision:
- Removed spinlock. - Suggested by Luis and Stephen
- Renamed `struct kunit_module` to `struct kunit_suite`. - Inspired by
  Luis.
- Made a number of minor cleanups. - Suggested by Luis and Stephen.
---
 include/kunit/test.h | 182 +++++++++++++++++++++++++++++++++++++++++
 kunit/Kconfig        |  17 ++++
 kunit/Makefile       |   1 +
 kunit/test.c         | 190 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 390 insertions(+)
 create mode 100644 include/kunit/test.h
 create mode 100644 kunit/Kconfig
 create mode 100644 kunit/Makefile
 create mode 100644 kunit/test.c

diff --git a/include/kunit/test.h b/include/kunit/test.h
new file mode 100644
index 0000000000000..b34d9f2ac6f9c
--- /dev/null
+++ b/include/kunit/test.h
@@ -0,0 +1,182 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Base unit test (KUnit) API.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@xxxxxxxxxx>
+ */
+
+#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 s.
+ * @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.
+ *
+ * A brief note on locking:
+ *
+ * First off, we need to lock because in certain cases a user may want to use an
+ * expectation in a thread other than the thread that the test case is running
+ * in.
+ *
+ * The next point is that the locking should be safe in an irq context.
+ * Technically speaking a user should use a mock/fake irqchip or some other fake
+ * method to trigger an irq handler under test; however, the irq handler should
+ * think that it is in a real irq context. Given that the code being run expects
+ * to be in an irq context, we should act as though it is.
+ */
+struct kunit {
+	void *priv;
+
+	/* private: internal use only. */
+	const char *name; /* Read only after initialization! */
+	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);
+
+/**
+ * suite_test() - 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.
+ *
+ * TODO(brendanhiggins@xxxxxxxxxx): 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 the current 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 the current 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 the current 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 */
diff --git a/kunit/Kconfig b/kunit/Kconfig
new file mode 100644
index 0000000000000..330ae83527c23
--- /dev/null
+++ b/kunit/Kconfig
@@ -0,0 +1,17 @@
+#
+# KUnit base configuration
+#
+
+menu "KUnit support"
+
+config KUNIT
+	bool "Enable support for unit tests (KUnit)"
+	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/.
+
+endmenu
diff --git a/kunit/Makefile b/kunit/Makefile
new file mode 100644
index 0000000000000..5efdc4dea2c08
--- /dev/null
+++ b/kunit/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_KUNIT) +=			test.o
diff --git a/kunit/test.c b/kunit/test.c
new file mode 100644
index 0000000000000..c030ba5a43e40
--- /dev/null
+++ b/kunit/test.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Base unit test (KUnit) API.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@xxxxxxxxxx>
+ */
+
+#include <linux/sched/debug.h>
+#include <kunit/test.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)
+{
+	spin_lock_init(&test->lock);
+	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;
+	int ret = 0;
+
+	kunit_init_test(&test, test_case->name);
+
+	if (suite->init) {
+		ret = suite->init(&test);
+		if (ret) {
+			kunit_err(&test, "failed to initialize: %d\n", ret);
+			kunit_set_failure(&test);
+			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);
+}
-- 
2.22.0.410.gd8fdbe21b5-goog