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POHow to test IO code in JUnit?
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  1. POHow to test IO code in JUnit?
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    copied!<p>I'm want to test two services:</p> <ol> <li>service which builds file name</li> <li>service which writes some data into file provided by 1st service</li> </ol> <p>In first i'm building some complex file structure (just for example <code>{user}/{date}/{time}/{generatedId}.bin</code>)</p> <p>In second i'm writing data to the file passed by first service (1st service calls 2nd service)</p> <p>How can I test both services using mocks without making any real IO interractions?</p> <p>Just for example:</p> <p>1st service:</p> <pre><code>public class DefaultLogService implements LogService { public void log(SomeComplexData data) { serializer.write(new FileOutputStream(buildComplexFileStructure()), data); or serializer.write(buildComplexFileStructure(), data); or serializer.write(new GenericInputEntity(buildComplexFileStructure()), data); } private ComplextDataSerializer serializer; // mocked in tests } </code></pre> <p>2nd service:</p> <pre><code>public class DefaultComplexDataSerializer implements ComplexDataSerializer { void write(InputStream stream, SomeComplexData data) {...} or void write(File file, SomeCompexData data) {...} or void write(GenericInputEntity entity, SomeComplexData data) {...} } </code></pre> <p>In first case i need to pass FileOutputStream which will create a file (i.e. i can't test 1st service)</p> <p>In second case i need to pass File. What can i do in 2nd service test if I need to test data which will be written to specified file? (i can't test 2nd service)</p> <p>In third case i think i need some generic IO object which will wrap File. Maybe there is some ready-to-use solution for this purpose?</p>
 

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