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  <div class="section" id="testing">
<h1>Testing<a class="headerlink" href="#testing" title="Permalink to this headline">¶</a></h1>
<p>Creating tests is one of the most important and also most difficult parts of developing Cassandra. There are different ways to test your code depending on what you&#8217;re working on.</p>
<div class="section" id="unit-testing">
<h2>Unit Testing<a class="headerlink" href="#unit-testing" title="Permalink to this headline">¶</a></h2>
<p>The most simple way to test code in Cassandra is probably by writing a unit test. Cassandra uses JUnit as a testing framework and test cases can be found in the <code class="docutils literal"><span class="pre">test/unit</span></code> directory. Ideally you’d be able to create a unit test for your implementation that would exclusively cover the class you created (the unit under test). Unfortunately this is not always possible and Cassandra doesn’t have a very mock friendly code base. Often you’ll find yourself in a situation where you have to make use of an embedded Cassandra instance that you’ll be able to interact with in your test. If you want to make use of CQL in your test, you can simply extend CQLTester and use some of the convenient helper methods such as in the following example.</p>
<div class="highlight-java"><div class="highlight"><pre><span></span><span class="nd">@Test</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">testBatchAndList</span><span class="o">()</span> <span class="kd">throws</span> <span class="n">Throwable</span>
<span class="o">{</span>
   <span class="n">createTable</span><span class="o">(</span><span class="s">&quot;CREATE TABLE %s (k int PRIMARY KEY, l list&lt;int&gt;)&quot;</span><span class="o">);</span>
   <span class="n">execute</span><span class="o">(</span><span class="s">&quot;BEGIN BATCH &quot;</span> <span class="o">+</span>
           <span class="s">&quot;UPDATE %1$s SET l = l +[ 1 ] WHERE k = 0; &quot;</span> <span class="o">+</span>
           <span class="s">&quot;UPDATE %1$s SET l = l + [ 2 ] WHERE k = 0; &quot;</span> <span class="o">+</span>
           <span class="s">&quot;UPDATE %1$s SET l = l + [ 3 ] WHERE k = 0; &quot;</span> <span class="o">+</span>
           <span class="s">&quot;APPLY BATCH&quot;</span><span class="o">);</span>

   <span class="n">assertRows</span><span class="o">(</span><span class="n">execute</span><span class="o">(</span><span class="s">&quot;SELECT l FROM %s WHERE k = 0&quot;</span><span class="o">),</span>
              <span class="n">row</span><span class="o">(</span><span class="n">list</span><span class="o">(</span><span class="mi">1</span><span class="o">,</span> <span class="mi">2</span><span class="o">,</span> <span class="mi">3</span><span class="o">)));</span>
<span class="o">}</span>
</pre></div>
</div>
<p>Unit tests can be run from the command line using the <code class="docutils literal"><span class="pre">ant</span> <span class="pre">test</span></code> command, <code class="docutils literal"><span class="pre">ant</span> <span class="pre">test</span> <span class="pre">-Dtest.name=&lt;simple_classname&gt;</span></code> to execute a test suite or <code class="docutils literal"><span class="pre">ant</span> <span class="pre">testsome</span> <span class="pre">-Dtest.name=&lt;FQCN&gt;</span> <span class="pre">-Dtest.methods=&lt;testmethod1&gt;[,testmethod2]</span></code> for individual tests.  For example, to run all test methods in the <code class="docutils literal"><span class="pre">org.apache.cassandra.cql3.SimpleQueryTest</span></code> class, you would run:</p>
<div class="highlight-none"><div class="highlight"><pre><span></span>ant test -Dtest.name=SimpleQueryTest
</pre></div>
</div>
<p>To run only the <code class="docutils literal"><span class="pre">testStaticCompactTables()</span></code> test method from that class, you would run:</p>
<div class="highlight-none"><div class="highlight"><pre><span></span>ant testsome -Dtest.name=org.apache.cassandra.cql3.SimpleQueryTest -Dtest.methods=testStaticCompactTables
</pre></div>
</div>
<div class="section" id="long-running-tests">
<h3>Long running tests<a class="headerlink" href="#long-running-tests" title="Permalink to this headline">¶</a></h3>
<p>Test that consume a significant amount of time during execution can be found in the <code class="docutils literal"><span class="pre">test/long</span></code> directory and executed as a regular JUnit test or standalone program. Except for the execution time, there’s nothing really special about them. However, ant will execute tests under <code class="docutils literal"><span class="pre">test/long</span></code> only when using the <code class="docutils literal"><span class="pre">ant</span> <span class="pre">long-test</span></code> target.</p>
</div>
</div>
<div class="section" id="dtests">
<h2>DTests<a class="headerlink" href="#dtests" title="Permalink to this headline">¶</a></h2>
<p>One way of doing integration or system testing at larger scale is by using <a class="reference external" href="https://github.com/riptano/cassandra-dtest">dtest</a>, which stands for “Cassandra Distributed Tests”. The idea is to automatically setup Cassandra clusters using various configurations and simulate certain use cases you want to test. This is done using Python scripts and <code class="docutils literal"><span class="pre">ccmlib</span></code> from the <a class="reference external" href="https://github.com/pcmanus/ccm">ccm</a> project. Dtests will setup clusters using this library just as you do running ad-hoc <code class="docutils literal"><span class="pre">ccm</span></code> commands on your local machine. Afterwards dtests will use the <a class="reference external" href="http://datastax.github.io/python-driver/installation.html">Python driver</a> to interact with the nodes, manipulate the file system, analyze logs or mess with individual nodes.</p>
<p>Using dtests helps us to prevent regression bugs by continually executing tests on the <a class="reference external" href="http://cassci.datastax.com/">CI server</a> against new patches. For frequent contributors, this Jenkins is set up to build branches from their GitHub repositories. It is likely that your reviewer will use this Jenkins instance to run tests for your patch. Read more on the motivation behind the CI server <a class="reference external" href="http://www.datastax.com/dev/blog/cassandra-testing-improvements-for-developer-convenience-and-confidence">here</a>.</p>
<p>The best way to learn how to write dtests is probably by reading the introduction &#8220;<a class="reference external" href="http://www.datastax.com/dev/blog/how-to-write-a-dtest">How to Write a Dtest</a>&#8221; and by looking at existing, recently updated tests in the project. New tests must follow certain <a class="reference external" href="https://github.com/riptano/cassandra-dtest/blob/master/CONTRIBUTING.md">style conventions</a> that are being checked before accepting contributions. In contrast to Cassandra, dtest issues and pull-requests are managed on github, therefor you should make sure to link any created dtests in your Cassandra ticket and also refer to the ticket number in your dtest PR.</p>
<p>Creating a good dtest can be tough, but it should not prevent you from submitting patches! Please ask in the corresponding JIRA ticket how to write a good dtest for the patch. In most cases a reviewer or committer will able to support you, and in some cases they may offer to write a dtest for you.</p>
</div>
<div class="section" id="performance-testing">
<h2>Performance Testing<a class="headerlink" href="#performance-testing" title="Permalink to this headline">¶</a></h2>
<p>Performance tests for Cassandra are a special breed of tests that are not part of the usual patch contribution process. In fact you can contribute tons of patches to Cassandra without ever running performance tests. They are important however when working on performance improvements, as such improvements must be measurable.</p>
<div class="section" id="cassandra-stress-tool">
<h3>Cassandra Stress Tool<a class="headerlink" href="#cassandra-stress-tool" title="Permalink to this headline">¶</a></h3>
<p>TODO: <a class="reference external" href="https://issues.apache.org/jira/browse/CASSANDRA-12365">CASSANDRA-12365</a></p>
</div>
<div class="section" id="cstar-perf">
<h3>cstar_perf<a class="headerlink" href="#cstar-perf" title="Permalink to this headline">¶</a></h3>
<p>Another tool available on github is <a class="reference external" href="https://github.com/datastax/cstar_perf">cstar_perf</a> that can be used for intensive performance testing in large clusters or locally. Please refer to the project page on how to set it up and how to use it.</p>
</div>
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