Unit testing... how to improve it

Question

I want to test a piece of code which returns an object.

I use NUnit and in a test class, I write a method to test if my method works fine...

[Test]
public void GetMyObjectFromLog()
{
     string _xmlFilePath = @"C:\XmlFile.xml";
     MyObjectParser _myObjectParser = new MyObjectParser();
     MyObject _mockMyObject = new MyObject
                              {
                                   Title = "obj",
                                   Name = "objName"
                              }
     MyObject _myObject = _myObjectParser.GetMyObjectFromLog(_xmlFilePath);

     Assert.AreEqual(_mockMyObject , _myObject);
}

This test does not work because MyObject does not override Equals method, and I don't want to override Equals method just for test purpose.

So I rewrite the test like this :

[Test]
public void GetMyObjectFromLog()
{
     string _xmlFilePath = @"C:\XmlFile.xml";
     MyObjectParser _myObjectParser = new MyObjectParser();
     MyObject _myObject = _myObjectParser.GetMyObjectFromLog(_xmlFilePath);

     Assert.AreEqual("obj", _myObject.Title);
     Assert.AreEqual("objName", _myObject.Name);
}

Ok, it works... but is this test is pertinent ? Moreover, there is a dependance to a file.

Is it pertinent to use a Mock Framework instead of ? And how to use it ?

Thank you !

Answer 1

About that dependency on the file (that even appears not to be in the project!):

You could override that _myObjectParser.GetMyObjectFromLog to also accept a Stream. Then you can add that XML file as embedded resource and read it from the assembly.

Answer 2

First of all, the method inside the parser should be name "Parse" instead of "Get".

Second of all, if you don't want the object itself to be able to compare itself to another, then it's perfectly fine to compare them just like you did (property by property). But this can be extracted into a helper method in the test class.

And lastly, you don't really want to tight-couple your parser with a file. You just want to parse text. If you want to include a static helper method that also opens a file and everything, that's your choice, but it shouldn't be a pure instance dependency.

[Test]
public void ParsesObjectFromXml()
{
     string xmlInput = " ... ";
     MyObjectXmlParser parser = new MyObjectXmlParser();
     MyObject expected = new MyObject() {Title = "obj", Name="objName"};

     AssertMyObjectsAreEqual(expected, parser.Parse(xmlInput));
}

private bool AssertMyObjectsAreEqual(MyObject expected, MyObject actual)
{
     Assert.AreEqual(expected.Title, actual.Title);
     Assert.AreEqual(expected.Name, actual.Name);
}

Now both your class and your test are clearer and only have a single responsibility.