Testing what's written to a Java OutputStream

java junit outputstream
Ciryon picture Ciryon · Oct 22, 2008 · Viewed 19k times · Source

I am about to write junit tests for a XML parsing Java class that outputs directly to an OutputStream. For example xmlWriter.writeString("foo"); would produce something like <aTag>foo</aTag> to be written to the outputstream held inside the XmlWriter instance. The question is how to test this behaviour. One solution would of course be to let the OutputStream be a FileOutputStream and then read the results by opening the written file, but it isn't very elegant.

Answer

Jon Skeet picture Jon Skeet · Oct 22, 2008

Use a ByteArrayOutputStream and then get the data out of that using toByteArray(). This won't test how it writes to the stream (one byte at a time or as a big buffer) but usually you shouldn't care about that anyway.

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