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Question

How do you avoid creating superfluous Strings when unit testing?

For example the String "SERIALIZED" seems a bit unnecessary and arbitrary..what would you use instead?

    Object update=new Object(); 
    FileWriter writer=mock(FileWriter.class);
    Serializer serializer=mock(Serializer.class);
    when(cache.getWriter(update)).thenReturn(writer);
    when(serializer.serialize(update)).thenReturn("SERIALIZED");

    FileRecorder recorder=new FileRecorder(serializer);
    recorder.receive(update);
    verify(writer).write("SERIALIZED");

Answer 1

I wouldn't call strings you use to verify whether your test passes superfluous . However, way you do it calls for a bit of refactoring:

• what "SERIALIZED" stands for? Will you be able to recall its purpose in, say, 2 months?
• you use same string twice, simple typo (which happen) will break your test. And that's something you want to avoid

I suggest refactoring it into a test suite-wide constant (or test method-wide , if that single test is only place you use it). And give it proper name:

final String FAKED_SERIALIZER_OUTPUT = "Any random content";
Object update=new Object(); 
FileWriter writer=mock(FileWriter.class);
Serializer serializer=mock(Serializer.class);
when(cache.getWriter(update)).thenReturn(writer);
when(serializer.serialize(update)).thenReturn(FAKED_SERIALIZER_OUTPUT);

FileRecorder recorder=new FileRecorder(serializer);
recorder.receive(update);
verify(writer).write(FAKED_SERIALIZER_OUTPUT);

Note that content of the string becomes irrelevant, considering variable name describes its purpose correctly.