discourse/lib/turbo_tests/flaky/manager.rb

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DEV: Introduce automatic reruns to RSpec tests on Github actions (#24811) What motivated this change? Our builds on Github actions have been extremely flaky mostly due to system tests. This has led to a drop in confidence in our test suite where our developers tend to assume that a failed job is due to a flaky system test. As a result, we have had occurrences where changes that resulted in legitimate test failures are merged into the `main` branch because developers assumed it was a flaky test. What does this change do? This change seeks to reduce the flakiness of our builds on Github Actions by automatically re-running RSpec tests once when they fail. If a failed test passes subsequently in the re-run, we mark the test as flaky by logging it into a file on disk which is then uploaded as an artifact of the Github workflow run. We understand that automatically re-runs will lead to lower accuracy of our tests but we accept this as an acceptable trade-off since a fragile build has a much greater impact on our developers' time. Internally, the Discourse development team will be running a service to fetch the flaky tests which have been logged for internal monitoring. How is the change implemented? 1. A `--retry-and-log-flaky-tests` CLI flag is added to the `bin/turbo_rspec` CLI which will then initialize `TurboTests::Runner` with the `retry_and_log_flaky_tests` kwarg set to `true`. 2. When the `retry_and_log_flaky_tests` kwarg is set to `true` for `TurboTests::Runner`, we will register an additional formatter `Flaky::FailuresLoggerFormatter` to the `TurboTests::Reporter` in the `TurboTests::Runner#run` method. The `Flaky::FailuresLoggerFormatter` has a simple job of logging all failed examples to a file on disk when running all the tests. The details of the failed example which are logged can be found in `TurboTests::Flaky::FailedExample.to_h`. 3. Once all the tests have been run once, we check the result for any failed examples and if there are, we read the file on disk to fetch the `location_rerun_location` of the failed examples which is then used to run the tests in a new RSpec process. In the rerun, we configure a `TurboTests::Flaky::FlakyDetectorFormatter` with RSpec which removes all failed examples from the log file on disk since those examples are not flaky tests. Note that if there are too many failed examples on the first run, we will deem the failures to likely not be due to flaky tests and not re-run the test failures. As of writing, the threshold of failed examples is set to 10. If there are more than 10 failed examples, we will not re-run the failures.
2023-12-13 07:18:27 +08:00
# frozen_string_literal: true
module TurboTests
module Flaky
class Manager
PATH = Rails.root.join("tmp/turbo_rspec_flaky_tests.json")
def self.potential_flaky_tests
JSON
.parse(File.read(PATH))
.map { |failed_example| failed_example["location_rerun_argument"] }
end
def self.remove_flaky_tests
File.delete(PATH) if File.exist?(PATH)
end
DEV: Introduce automatic reruns to RSpec tests on Github actions (#24811) What motivated this change? Our builds on Github actions have been extremely flaky mostly due to system tests. This has led to a drop in confidence in our test suite where our developers tend to assume that a failed job is due to a flaky system test. As a result, we have had occurrences where changes that resulted in legitimate test failures are merged into the `main` branch because developers assumed it was a flaky test. What does this change do? This change seeks to reduce the flakiness of our builds on Github Actions by automatically re-running RSpec tests once when they fail. If a failed test passes subsequently in the re-run, we mark the test as flaky by logging it into a file on disk which is then uploaded as an artifact of the Github workflow run. We understand that automatically re-runs will lead to lower accuracy of our tests but we accept this as an acceptable trade-off since a fragile build has a much greater impact on our developers' time. Internally, the Discourse development team will be running a service to fetch the flaky tests which have been logged for internal monitoring. How is the change implemented? 1. A `--retry-and-log-flaky-tests` CLI flag is added to the `bin/turbo_rspec` CLI which will then initialize `TurboTests::Runner` with the `retry_and_log_flaky_tests` kwarg set to `true`. 2. When the `retry_and_log_flaky_tests` kwarg is set to `true` for `TurboTests::Runner`, we will register an additional formatter `Flaky::FailuresLoggerFormatter` to the `TurboTests::Reporter` in the `TurboTests::Runner#run` method. The `Flaky::FailuresLoggerFormatter` has a simple job of logging all failed examples to a file on disk when running all the tests. The details of the failed example which are logged can be found in `TurboTests::Flaky::FailedExample.to_h`. 3. Once all the tests have been run once, we check the result for any failed examples and if there are, we read the file on disk to fetch the `location_rerun_location` of the failed examples which is then used to run the tests in a new RSpec process. In the rerun, we configure a `TurboTests::Flaky::FlakyDetectorFormatter` with RSpec which removes all failed examples from the log file on disk since those examples are not flaky tests. Note that if there are too many failed examples on the first run, we will deem the failures to likely not be due to flaky tests and not re-run the test failures. As of writing, the threshold of failed examples is set to 10. If there are more than 10 failed examples, we will not re-run the failures.
2023-12-13 07:18:27 +08:00
# This method should only be called by a formatter registered with `TurboTests::Runner` and logs the failed examples
# to `PATH`. See `FailedExample#to_h` for the details of each example that is logged.
#
# @param [Array<TurboTests::FakeExample>] failed_examples
def self.log_potential_flaky_tests(failed_examples)
return if failed_examples.empty?
File.open(PATH, "w") do |file|
file.puts(
failed_examples.map { |failed_example| FailedExample.new(failed_example).to_h }.to_json,
)
end
end
# This method should only be called by a formatter registered with `RSpec::Core::Formatters.register` and removes
# the given examples from the log file at `PATH` by matching the `location_rerun_argument` of each example.
#
# @param [Array<RSpec::Core::Example>] failed_examples
def self.remove_example(failed_examples)
flaky_tests =
JSON
.parse(File.read(PATH))
.reject do |failed_example|
failed_examples.any? do |example|
failed_example["location_rerun_argument"] == example.location_rerun_argument
end
end
if flaky_tests.present?
File.write(PATH, flaky_tests.to_json)
else
File.delete(PATH)
end
end
end
end
end