View source for Manual:Writing testable PHP code

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{{Manual:PHP unit testing/navigation}}
<translate><!--T:1--> Some notes on writing testable, code, to be expanded on at some point.</translate>

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== Don't assume global context == <!--T:2-->

<!--T:3-->
Accessing global variables (e.g. <tvar|1><code>$wgRequest</code></>) without declaring them first with the <tvar|2><code>global</code></> keyword will cause failures and <tvar|3>E_NOTICE</> messages to be generated if they are accessed in a non-global context.

== Don't create new global variables == <!--T:4-->
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<translate><!--T:5--> While putting information in global variables seems easy, it makes the code less predictable.</translate>
<translate><!--T:6--> By relying on global variables, you are making it difficult to isolate functionality.</translate>
<translate><!--T:7--> A singleton class is better for testing (but, still, less than ideal).</translate>

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== Rely only on direct inputs == <!--T:8-->
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<translate><!--T:9--> While this is not always achievable, it is best to write code that depends only on direct inputs.</translate>
<translate><!--T:10--> That is, a class only uses the information it is passed and does not rely on singletons or globals to get “out-of-band” information.</translate>

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== Do not use <tvar|1><code>exit()</code></> == <!--T:11-->
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<translate><!--T:12--> Exiting from a script abruptly should almost never be done.</translate>
<translate><!--T:13--> Doing so will make your code untestable by PHPUnit.</translate>
<translate><!--T:14--> If your code encounters an unexpected error, the proper thing to do is throw an exception like:</translate>

<syntaxhighlight lang="php">
throw new MWException( "Oh noes!" );
</syntaxhighlight>

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<!--T:15-->
This will allow PHPUnit and MediaWiki to exit properly and provide informative information such as stack traces to developers.

== External resources == <!--T:16-->
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* [https://www.youtube.com/watch?v=XcT4yYu_TTs <translate><!--T:18--> How to Write Clean, Testable Code techtalk by Miško Hevery</translate>]

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