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c#unit-testingtestingintegration-testing
Ingrid Morstrad
Ingrid Morstrad

Reputation: 187

Integration testing for reading a file

I want to make sure that my C# program reads a file as expected. How should I test this? I am assuming I just call my function (which accesses the file system) and see the output when a file exist and when it doesn't. Should I instead abstract the file system out?

Should I even bother testing this (since I am basically testing if StreamReader.ReadLine works)?

My function looks like this (filePath, filePath2, a and b are arguments to the function)

try
{
    TextReader tr = new StreamReader(filePath);

    a = tr.ReadLine();
    b = tr.ReadLine();
    tr.Close();
}
catch (Exception ex)
{
    error = GetError(ex);
}
if (error != "") {
    File.WriteAllText(filePath2+"Error.txt", error);
}

Upvotes: 0

Views: 687

Answers (1)

Alexei Levenkov
Alexei Levenkov

Reputation: 100527

Two most common approaches: facade for all file IO operations (so you can mock it) or refactor code that you only need to test pieces that take easy to mock objects like Stream.

Sample second approach: refactor your code into piece that deals with getting stream and another one that actually read the data:

public class MyClass 
{
  .............
  string a;
  string b;
  public ReadTheData(Stream stream)
  {
    try
    {
        TextReader tr = new StreamReader(stream);

        a = tr.ReadLine();
        b = tr.ReadLine();
        tr.Close();
    }
    catch (Exception ex)
    {
        // awful practice... Don't eat all exceptions
        error = GetError(ex);
    }
    if (error != "") {
       // whatever log infrastructure you have, need to be mock-able for tests 
        Logger.Log(error);
    }
  }
}

Now you can unit test ReadTheData method without any access to file system by passing filled out MemoryStream or even mocked out stream.

Upvotes: 1

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