kunit: tool: print summary of failed tests if a few failed out of a lot

E.g. all the hw_breakpoint tests are failing right now.
So if I run `kunit.py run --altests --arch=x86_64`, then I see
> Testing complete. Ran 408 tests: passed: 392, failed: 9, skipped: 7

Seeing which 9 tests failed out of the hundreds is annoying.
If my terminal doesn't have scrollback support, I have to resort to
looking at `.kunit/test.log` for the `not ok` lines.

Teach kunit.py to print a summarized list of failures if the # of tests
reachs an arbitrary threshold (>=100 tests).

To try and keep the output from being too long/noisy, this new logic
a) just reports "parent_test failed" if every child test failed
b) won't print anything if there are >10 failures (also arbitrary).

With this patch, we get an extra line of output showing:
> Testing complete. Ran 408 tests: passed: 392, failed: 9, skipped: 7
> Failures: hw_breakpoint

This also works with parameterized tests, e.g. if I add a fake failure
> Failures: kcsan.test_atomic_builtins_missing_barrier.threads=6

Note: we didn't have enough tests for this to be a problem before.
But with commit 980ac3ad05 ("kunit: tool: rename all_test_uml.config,
use it for --alltests"), --alltests works and thus running >100 tests
will probably become more common.

Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/kunit/kunit_parser.py

@@ -58,6 +58,10 @@ class Test:
 		self.counts.errors += 1
 		stdout.print_with_timestamp(stdout.red('[ERROR]') + f' Test: {self.name}: {error_message}')
 
+	def ok_status(self) -> bool:
+		"""Returns true if the status was ok, i.e. passed or skipped."""
+		return self.status in (TestStatus.SUCCESS, TestStatus.SKIPPED)
+
 class TestStatus(Enum):
 	"""An enumeration class to represent the status of a test."""
 	SUCCESS = auto()
@@ -565,6 +569,40 @@ def print_test_footer(test: Test) -> None:
 	stdout.print_with_timestamp(format_test_divider(message,
 		len(message) - stdout.color_len()))
 
+
+
+def _summarize_failed_tests(test: Test) -> str:
+	"""Tries to summarize all the failing subtests in `test`."""
+
+	def failed_names(test: Test, parent_name: str) -> List[str]:
+		# Note: we use 'main' internally for the top-level test.
+		if not parent_name or parent_name == 'main':
+			full_name = test.name
+		else:
+			full_name = parent_name + '.' + test.name
+
+		if not test.subtests:  # this is a leaf node
+			return [full_name]
+
+		# If all the children failed, just say this subtest failed.
+		# Don't summarize it down "the top-level test failed", though.
+		failed_subtests = [sub for sub in test.subtests if not sub.ok_status()]
+		if parent_name and len(failed_subtests) ==  len(test.subtests):
+			return [full_name]
+
+		all_failures = []  # type: List[str]
+		for t in failed_subtests:
+			all_failures.extend(failed_names(t, full_name))
+		return all_failures
+
+	failures = failed_names(test, '')
+	# If there are too many failures, printing them out will just be noisy.
+	if len(failures) > 10:  # this is an arbitrary limit
+		return ''
+
+	return 'Failures: ' + ', '.join(failures)
+
+
 def print_summary_line(test: Test) -> None:
 	"""
 	Prints summary line of test object. Color of line is dependent on
@@ -587,6 +625,15 @@ def print_summary_line(test: Test) -> None:
 		color = stdout.red
 	stdout.print_with_timestamp(color(f'Testing complete. {test.counts}'))
 
+	# Summarize failures that might have gone off-screen since we had a lot
+	# of tests (arbitrarily defined as >=100 for now).
+	if test.ok_status() or test.counts.total() < 100:
+		return
+	summarized = _summarize_failed_tests(test)
+	if not summarized:
+		return
+	stdout.print_with_timestamp(color(summarized))
+
 # Other methods:
 
 def bubble_up_test_results(test: Test) -> None:

tools/testing/kunit/kunit_tool_test.py

@@ -312,6 +312,28 @@ class KUnitParserTest(unittest.TestCase):
 				result.status)
 			self.assertEqual('kunit-resource-test', result.subtests[0].name)
 
+	def test_summarize_failures(self):
+		output = """
+		KTAP version 1
+		1..2
+			# Subtest: all_failed_suite
+			1..2
+			not ok 1 - test1
+			not ok 2 - test2
+		not ok 1 - all_failed_suite
+			# Subtest: some_failed_suite
+			1..2
+			ok 1 - test1
+			not ok 2 - test2
+		not ok 1 - some_failed_suite
+		"""
+		result = kunit_parser.parse_run_tests(output.splitlines())
+		self.assertEqual(kunit_parser.TestStatus.FAILURE, result.status)
+
+		self.assertEqual(kunit_parser._summarize_failed_tests(result),
+			'Failures: all_failed_suite, some_failed_suite.test2')
+
+
 def line_stream_from_strs(strs: Iterable[str]) -> kunit_parser.LineStream:
 	return kunit_parser.LineStream(enumerate(strs, start=1))