[jira] [Resolved] (HBASE-4712) Document rules for writing tests

["stack (Resolved) (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-4712?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

stack resolved HBASE-4712.
--------------------------

       Resolution: Fixed
    Fix Version/s: 0.94.0
     Hadoop Flags: Reviewed

Committed to trunk.  Thanks for the doc. N.
                
> Document rules for writing tests
> --------------------------------
>
>                 Key: HBASE-4712
>                 URL: https://issues.apache.org/jira/browse/HBASE-4712
>             Project: HBase
>          Issue Type: Task
>          Components: test
>    Affects Versions: 0.92.0
>            Reporter: nkeywal
>            Assignee: nkeywal
>            Priority: Minor
>             Fix For: 0.94.0
>
>         Attachments: 4712.txt
>
>
> We saw that some tests could be improved. Documenting the general rules could help.
> Proposal:
> HBase tests are divided in three categories: small, medium and large, with corresponding JUnit categories: SmallTest, MediumTest, LargeTest
> Small tests are executed in parallel in a shared JVM. They must last less than 15 seconds. They must NOT use a cluster.
> Medium tests are executed in separate JVM. They must last less than 50 seconds. They can use a cluster. They must not fail occasionally.
> Small and medium tests must not need more than 30 minutes to run altogether.
> Small and medium tests should be executed by the developers before submitting a patch.
> Large tests are everything else. They are typically integration tests, non-regression tests for specific bugs, timeout tests, performance tests.
> Tests rules & hints are:
> - As most as possible, tests should be written as small tests.
> - All tests should be written to support parallel execution on the same machine, hence should not use shared resources as fixed ports or fixed file names.
> - All tests should be written to be as fast as possible.
> - 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 function to create a temp directory and do the cleanup, or to start a cluster.
> - Sleeps:
>     - 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 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 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.

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