Question

Apparently i have been struggling to test an application built by Developers in my Ourteam.
The Class:Apis, Reads the connection string,id and error message from user.I return a dictionary of values name, and Qualification weight.Because am a newbie in Testing am facing alot problem to get my test working as expected.Please advise where am not doing wrong.
Class:

 public class Apis
{

    public Dictionary<String, String> getQualWeight(String sqlConStr, String inBin, Label lblResults)
    {
        Dictionary<String, String> qualList = new Dictionary<string, string>();
        string selectSQL = "select Name,qual_weight from Qualification_type "
                            + "where ID in (select Qualification_ID from Qualifications where BIN = @inBin)";
        con = getConn(sqlConStr);
        SqlCommand cmd = new SqlCommand(selectSQL, con);
        cmd.Parameters.AddWithValue("@inBin", inBin);
        SqlDataReader reader;
        try
        {
            con.Open();
            reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                qualList.Add(reader[0].ToString(), reader[1].ToString());
            }
            reader.Close();
            return qualList;
        }
        catch (Exception err)
        {
            lblResults.Text = "error fetching qualification weight " + err.Message;
            return null;
        }
        finally
        {
            con.Close();
        }
    }    

My test:

[TestMethod()]
    public void getQualWeightTest()
    {
        Api target = new Api();
        string sqlConStr = "SERVER=ABC123; Database=DB; UID=id; PWD=passme;encrypt=no;enlist=false";
        string inBin = "2012-52-456"; 
        Label lblResults = null;

        lblResults.Text = " Failed";
        Dictionary<string, string> expected = new Dictionary<string,string>();
        expected.Add("Gohn", "50");
        Dictionary<string, string> actual;
        actual = target.getQualWeight(sqlConStr, inBin, lblResults);
        Assert.AreEqual(expected, actual);

    }

Answer 1

Just looking at your code I have a couple of suggestions.

1. You don’t want to rely on an external resource (in this case the Database) in your unit tests. Your code could be fine but the test could fail if this database is down. Look at something like the Repository Pattern and pass in (or ideally inject using Dependency Injection) a repository rather than a connection string. Using this approach you can use a ‘Fake’ repository and you have complete control over the data being passed back and you remove the dependency on the database. You can also test your repository in isolation if need be.
2. This code looks like it is in violation of the Single Responsibility Principle, it is responsible for Data Access and updating the UI. Calling out to a repository would remove the data access from the code and make it easier to test.

I find a good indicator of how decoupled your code is is how easy it is to test. If your having difficulty testing your code, it could be a candidate for refactoring.