MStest throwing errors for Class library using multiple config files

Question

I have created a class library MultipleConfigFiles, which has a method getConfigData. This method reads data from config files.

 public class Class1
    {
      public string getConfigData()
      {
        string configData = ConfigurationManager.AppSettings["key"].ToString();
        return configData;
      }
    }

Now I have a console application ConsoleAppConfig, in which I have given the reference of the class library.In the main method, I have created a object for the library class and called the method.

static void Main(string[] args)
        {
            Class1 c = new Class1();
            string data = c.getConfigData();
            Console.Write(data);    
        }

This console application has 2 different config files dev.config and prod.config. In the main App.config file , I have used configSource to map the appropriate config file.

<appSettings configSource="dev.config" />

Dev.config file looks like this:

<?xml version="1.0" encoding="utf-8" ?>
<appSettings>
    <add key="key" value="dev" />
</appSettings>

Till here it is working fine.That is, when I run the console app, the method returns dev.

Now,I have created a MSTest project for this class library.

public class Class1Tests
    {
        [TestMethod()]
        public void getConfigDataTest()
        {
            Class1 obj = new Class1();
            var result = obj.getConfigData();                
        }
    }

Now the problem is, when I run this test, it throws an error saying
"An exception of type 'System.NullReferenceException' occurred in MultipleConfigFiles.dll but was not handled in user code. Additional information: Object reference not set to an instance of an object."

Since the config files are in ConsoleApplication , the method is not able to read the appsetting variables from there. Is there any way I can maintain the configuration files globally so that both of them use individually , or is there any better way to handle this.

Any inputs are appreciated.Thanks.

Answer 1

Without duplicating the files you can the Link the files in existing Unit Test project. You can try the same as mentioned in the image Link (https://grantwinney.com/content/images/2014/04/AddExistingFileAsLink-002.png)

Google this term "Visual Studio - Add File As Link" for more Info

Image Credits : https://grantwinney.com