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From Todd Lipcon <t...@cloudera.com>
Subject Re: unit tests
Date Mon, 28 Nov 2011 23:10:20 GMT
Haven't had a chance to review the full note below, but one request:
can we please put this in the code tree itself in a file like
TESTING.txt or README.testing.txt or something?

It'd be nice to be able to refer back to it from within the code tree.

-Todd

On Mon, Nov 28, 2011 at 12:29 PM, N Keywal <nkeywal@gmail.com> wrote:
> Hi,
>
> The surefire modification seems to work well, so we can move to the final
> step.
> Please find below the last proposition for the test. The behavior described
> can be activated with:
>  - a commit of hbase-4847
>  - a modification of the jenkins config to run mvn verify vs. mvn tests.
>
> The main points are:
>  - should we run small & medium tests only by default on a developer
> machine => here answer is yes
>  - should we run all tests on the central build => here answer is yes
>  - should we stop when a small test fails => here answer is yes
>  - should we stop when a medium test fails => here answer is yes
>
>
> Also, I just had a discussion with Jesse, who think we should keep/have the
> notion of integration test. If retained, the points above must be impacted
> to take this into account.
>
>
> fyi, there are today:
>  - 416 small tests, executed in ~3 minutes
>  - 489 medium tests, executed in ~35 minutes (without parallelization)
>  - 280 large tests, executed in ~90 minutes (without parallelization)
>
> --
> 1) Running tests
> HBase tests are divided in three categories: small, medium and large, with
> corresponding JUnit categories: SmallTests, MediumTests, LargeTests.
>
> - Small tests are executed in a shared JVM. We put in this category all the
> tests that can be executed quickly (the maximum execution time for a test
> is 15 seconds, and they do not use a cluster) in a shared jvm.
> - Medium tests represents tests that must be executed before proposing a
> patch. They are designed to run in less than 30 minutes altogether, and are
> quite stable in their results. They're designed to last less than 50
> seconds individually. They can use a cluster, and each of them is executed
> in a separate JVM.
> - Large tests are everything else. They are typically integration tests,
> regression tests for specific bugs, timeout tests, performance tests. Some
> of them can be flaky. They are executed before a commit on the
> pre-integration machines. They can be run on the developer machine as well.
>
> Commands are:
> 1) mvn test
>  - execute small tests in a single JVM and medium tests in a separate JVM
> for each test
>  - medium tests are NOT executed if there is an error in a small test
>  - large tests are NOT executed
>  - there is one report for small tests, and one report for medium tests -if
> they are executed-
>
> 2) mvn verify
>  - execute small tests in a single JVM then medium tests in a separate JVM
> for each test, then large tests in a separate JVM as well.
>  - medium tests are NOT executed if there is an error in a small test
>  - large tests are NOT executed if there is an error in a small or medium
> test
>  - there is one report by test category, small, medium and large
>
> 3) mvn test -P localTests -Dtest=myTests
>  - remove any category effect (without this specific profile, the profiles
> are taken into account)
>  - use actually the official release of surefire & the old connector to
> junit
>  - tests are executed in separated JVM
> - You will see a new message at the end of the report: "[INFO] Tests are
> skipped". It's harmless.
>
> 4) mvn test -P runAllTests
>  - execute small tests in a single JVM then medium & large tests in a
> separate JVM for each test
>  - medium and large tests are NOT executed if there is an error in a small
> test
>  - large tests are NOT executed if there is an error in a small or medium
> test
>  - there are one report for small tests, and one report for medium & large
> tests -if they are executed-
>
> 5) Various other profiles
>  - mvn test -P runSmallTests   - execute small tests only,  in a single JVM.
>  - mvn test -P runMediumTests   - execute medium tests in a single JVM.
>  - mvn test -P runLargeTests   - execute medium tests in a single JVM.
>
> It's as well possible to use the script 'hbasetests.sh'. This script runs
> the medium and large tests in parallel with two maven instances, and
> provide a single report. It must be executed from the directory which
> contains the pom.xml. Commands are:
> ./dev-support/hbasetests.sh              - execute small and medium tests
> ./dev-support/hbasetests.sh runAllTests  - execute all tests
> ./dev-support/hbasetests.sh replayFailed - rerun the failed tests a second
> time, in a separate jvm and without parallelisation.
>
> 2) Writing tests
> Tests rules & hints are:
> - As most as possible, tests should be written as small tests.
> - All tests must be written to support parallel execution on the same
> machine, hence should not use shared resources as fixed ports or fixed file
> names.
> - Tests should not overlog. More than 100 lines/second makes the logs
> complex to read and use i/o that are hence not available for the other
> tests.
> - Tests can be written with HBaseTestingUtility . This class offers helper
> functions to create a temp directory and do the cleanup, or to start a
> cluster.
>
> - Categories and execution time
>  - All tests must be categorized, if not they could be skipped.
>  - All tests should be written to be as fast as possible.
>  - Small tests should last less than 15 seconds, and must not have any
> side effect.
>  - Medium tests should last less than 45 seconds.
>  - large tests should last less than 3 minutes, this ensure a good
> parallelization for the ones using it, and ease the analysis when the test
> fails.
>
> - Sleeps:
>    - Whenever possible, tests should not use sleep, but rather waiting for
> the real event. This is faster and clearer for the reader.
>    - Tests should not do a 'Thread.sleep' without testing an ending
> condition. This allows understanding what the test is waiting for.
> Moreover, the test will work whatever the machine performances.
>    - Sleep should be minimal to be as fast as possible. Waiting for a
> variable should be done in a 40ms sleep loop. Waiting for a socket
> operation should be done in a 200 ms sleep loop.
>
> - Tests using  a cluster:
>    - Tests using a HRegion do not have to start a cluster: A region can
> use the local file system.
>    - Start/stopping a cluster cost around 10 seconds. They should not be
> started per test method but per test class.
>    - Started cluster must be shutdown using
> HBaseTestingUtility#shutdownMiniCluster, which cleans the directories.
>    - As most as possible, tests should use the default settings for the
> cluster. When they don't, they should document it. This will allow to share
> the cluster later.
>



-- 
Todd Lipcon
Software Engineer, Cloudera

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