How to write unit tests for code, which uses FreeMarker templates?

I am going to use a templat开发者_如何学编程e engine in Java (probably FreeMarker). Now I wonder how to write a unit test for it.

I can prepare an expected output as a text file but I will have to change it manually whenever I change the template. I would like to parse the output using the template to get the model data and it with the original model. Can I do that?

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Depends on what your template will output. Of course if it produced a well formed format like XML or JSON you could easily parse it so I'm left to assume it's probably HTML. You might be able to use JTidy to parse it into a DOM model that can be used from Java.

http://jtidy.sourceforge.net/

Another option might be to use good old fashion grep routine, then build primitives like assertContains, assertDoesNotContain, etc. I have a JSON library I write unit tests for and I took that route to just do old fashion grep, and it's worked well in that it catches bugs. I worried about parsing the JSON code directly because I'd be using the code I wrote in my tests to test that very code. Your case might be different so parsing to a DOM model might make more sense.

The big thing, to consider, is you're testing the view. So as things change visually you might have a very hard time keeping your tests up to date. The view gets changed a lot in most programs because your client, PM, person in control of what you're doing, changes their mind frequently.