C# Unit Testing parser

Question

I need to write a parser. There are many input formats which I want to test and the output is pretty complex. How should I test different inputs and outputs with similar tests?

For example

public class Person
{
    public string Name;
    public int Age;
    public string Comment;
}

public interface IParser
{
    Person Parse(string input);
}

public class Parser : IParser
{
    public Person Parse( string input )
    {
        var fields = input.Split(',');

        var p = new Person
        {
            Name = fields[0],
            Age = int.Parse(fields[1])
        };

        p.Comment = fields.Length == 3 ? fields[2] : ""; 

        return p;
    }
}

I wrote these tests...

public class ParserTests
{
    protected string _input;
    protected Person _expected;

    private IParser _parser = new Parser();
    private Person _actual { get { return _parser.Parse(_input); } }

    [TestMethod]
    public void Parse_Name()
    {
        Assert.AreEqual(_expected.Name, _actual.Name);
    }

    [TestMethod]
    public void Parse_Age()
    {
        Assert.AreEqual(_expected.Age, _actual.Age);
    }

    [TestMethod]
    public void Parse_Comment()
    {
        Assert.AreEqual(_expected.Comment, _actual.Comment);
    }
}

[TestClass]
public class ParserTestsWithoutComment : ParserTests
{
    public ParserTestsWithoutComment()
    {
        _input = "John,29";
        _expected = new Person { Name = "John", Age = 29, Comment = "" };
    }
}

[TestClass]
public class ParserTestsWithComment : ParserTests
{
    public ParserTestsWithComment()
    {
        _input = "Brian,99,test";
        _expected = new Person { Name = "Brian", Age = 99, Comment = "test" };
    }
}

I'm new to unit testing and I'm not sure how to start with more complex stuff. My real input file is more complicated it's like

PokerStars Hand #98451585362:  Hold'em No Limit ($5/$10 USD) - 2013/05/12 9:25:04 CET [2013/05/12 3:25:04 ET]
Table 'Soyuz-Apollo II' 6-max Seat #4 is the button
Seat 1: Codrus426 ($1812.52 in chips) 
Seat 2: JMBigJoe ($2299.10 in chips) 
Seat 3: xinxin1 ($903.94 in chips) 
Seat 4: moshmachine ($1107 in chips) 
Seat 5: TopKat5757 ($1147 in chips) 
Seat 6: LukaschenkoA ($1274.96 in chips) 
TopKat5757: posts small blind $5
LukaschenkoA: posts big blind $10
*** HOLE CARDS ***
Codrus426: calls $10
JMBigJoe: raises $25 to $35
xinxin1: folds 
moshmachine: folds 
TopKat5757: folds 
LukaschenkoA: folds 
Codrus426: calls $25
*** FLOP *** [2h 3s 6h]
Codrus426: checks 
JMBigJoe: bets $41
Codrus426: calls $41
*** TURN *** [2h 3s 6h] [2d]
Codrus426: bets $40
JMBigJoe: calls $40
*** RIVER *** [2h 3s 6h 2d] [Qh]
Codrus426: checks 
JMBigJoe: checks 
*** SHOW DOWN ***
Codrus426: shows [9d Ah] (a pair of Deuces)
JMBigJoe: mucks hand 
Codrus426 collected $244 from pot
*** SUMMARY ***
Total pot $247 | Rake $3 
Board [2h 3s 6h 2d Qh]
Seat 1: Codrus426 showed [9d Ah] and won ($244) with a pair of Deuces
Seat 2: JMBigJoe mucked
Seat 3: xinxin1 folded before Flop (didn't bet)
Seat 4: moshmachine (button) folded before Flop (didn't bet)
Seat 5: TopKat5757 (small blind) folded before Flop
Seat 6: LukaschenkoA (big blind) folded before Flop

And I want parse it to a Hand class I'm working on...

public class Hand
{   
    public long ID; 
    public string Stakes; 
    public DateTime Date; 

    public IDictionary<Street, decimal> Pots;
    public decimal FinalPot; 
    public decimal Rake; 

    public Player Hero; 
    public IDictionary<Player, PlayerInfo> Players; 

    public IList<Card> Board; 

    public IList<Decision> Actions; 

    public Hand()
    { 
        this.Players = new Dictionary<Player, PlayerInfo>();
        this.Board = new List<Card>();
        this.Actions = new List<Decision>();
        this.Pots = new Dictionary<Street, decimal>();
    }
}

public class PlayerInfo
{
    public Player Player;
    public decimal Stack;
    public decimal Summary;
    public Position Position;
    public Card Holecards;
}

Answer 1

Your Solution is working but difficuilt to understand since you combine global variables with inheritance.

If you are using NUnit 2.5 or later you can use Parameterized Tests with TestCaseAttribute.

[TestCase("John,29","John",29,"")]
[TestCase(",13","",13,"")]
public void ParserTest(Sting stringToParse, String expextedName, int expectedAge, String expectedComment)
{
    IParser _parser = new Parser();
    Person _actual = _parser.Parse(stringToParse);

    Assert.AreEqual(expextedName, _actual.Name, stringToParse + " failed on Name");
    Assert.AreEqual(expextedAge, _actual.Age, stringToParse + " failed on Age");
    Assert.AreEqual(expextedComment, _actual.Comment, stringToParse + " failed on Comment");
}

I think this is much easier to understand.

If you need to stay with mstest you have to simulated it as decribed in how-to-rowtest-with-mstest

Answer 2

I think the structure you have is pretty good, bearing in mind that TMTOWTDI.

Be sure, however, to explicitly test Parse for null, empty (i.e. zero-length), and whitespace strings. More complicated/expected-path cases are key to test of course, but simple cases like this are important too.

Also, the structure you are using could very well be collapsed into ParserTests with a common %MethodUnderTest%_With%Condition(s)%_Expect%ExpectedResult% test-case naming convention and optionally the Test Data Builder pattern to make another class responsible for building test data like you are now doing in your ParserTests subclasses