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How to effectively test a parser with a fixed length of a flat file using MSpec?

I have this method signature: List<ITMData> Parse(string[] lines)

ITMData has 35 properties.

How would you effectively test such a parser?

Questions:

  • Should I download the whole file (can I use System.IO)?
  • Should I put a line from a file into a line constant?
  • Should I test one or more lines
  • Should I check every property of ITMData or check the whole object?
  • What about the name of my test?

EDIT

I replaced the method signature with ITMData Parse(string line).

Test code:

[Subject(typeof(ITMFileParser))]
public class When_parsing_from_index_59_to_79
{
    private const string Line = ".........";
    private static ITMFileParser _parser;
    private static ITMData _data;

    private Establish context = () => { _parser = new ITMFileParser(); };

    private Because of = () => { _data = _parser.Parse(Line); };

    private It should_get_fldName = () => _data.FldName.ShouldBeEqualIgnoringCase("HUMMELDUMM");
}

EDIT 2

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:

[Subject(typeof(ITMFileParser))]
public class When_parsing_single_line_from_ITM_file
{
    const string Line = ""

    static ITMFileParser _parser;
    static ITMData _data;

    Establish context = () => { _parser = new ITMFileParser(); };

    private Because of = () => { _data = _parser.Parse(Line); };

    It should_get_fld??? = () => _data.Fld???.ShouldEqual(???);
    It should_get_fld??? = () => _data.Fld???.ShouldEqual(???);
    It should_get_fld??? = () => _data.Fld???.ShouldEqual(???);
    It should_get_fld??? = () => _data.Fld???.ShouldEqual(???);
    It should_get_fld??? = () => _data.Fld???.ShouldEqual(???);
    It should_get_fld??? = () => _data.Fld???.ShouldEqual(???);
    It should_get_fld??? = () => _data.Fld???.ShouldEqual(???);
    ...

}
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public void Check_All_Properties_Parsed_Correctly(){.....}

public void Exception_Thrown_If_Lines_Is_Null(){.....}

public void Exception_Thrown_If_Lines_Is_Wrong_Length(){.....}

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EDIT:

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  • . CheckPropertyX, CheckPropertyY .. , , . , , . 2:
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Assert.AreEqual("test1", myObject.PropertyX, "Property X was incorrectly parsed"); Assert.AreEqual("test2", myObject.PropertyY, "Property Y was incorrectly parsed");

When one of them does not work, you will find out which line failed. When you correct the corresponding error and re-run your tests, you will see if any other properties have worked. This is usually the approach that most people take because creating a class or even a method for each property leads to too much code and too much work to update.

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