Reload app.config with nunit

Question

I have multiple NUnit tests, and I would like each test to use a specific app.config file. Is there a way to reset the configuration to a new config file before each test?

Answer 1

Try:

/* Usage
 * using(AppConfig.Change("my.config")) {
 *   // do something...
 * }
 */
public abstract class AppConfig : IDisposable
{
    public static AppConfig Change(string path)
    {
        return new ChangeAppConfig(path);
    }
    public abstract void Dispose();

    private class ChangeAppConfig : AppConfig
    {
        private bool disposedValue = false;
        private string oldConfig = Conversions.ToString(AppDomain.CurrentDomain.GetData("APP_CONFIG_FILE"));

        public ChangeAppConfig(string path)
        {
            AppDomain.CurrentDomain.SetData("APP_CONFIG_FILE", path);
            typeof(ConfigurationManager).GetField("s_initState", BindingFlags.NonPublic | BindingFlags.Static).SetValue(null, 0);
        }

        public override void Dispose()
        {
            if (!this.disposedValue)
            {
                AppDomain.CurrentDomain.SetData("APP_CONFIG_FILE", this.oldConfig);
            typeof(ConfigurationManager).GetField("s_initState", BindingFlags.NonPublic | BindingFlags.Static).SetValue(null, 0);
                this.disposedValue = true;
            }
            GC.SuppressFinalize(this);
        }
    }
}

Answer 2

If you issue is that you for different sets of test cases needs to have different configurations you can have different test projects with a configuration file for each. Then run your test projects one at a time.

Answer 3

I answered a similar question for Powershell. The same technique should work here, simply call the following at the start of your test:

System.AppDomain.CurrentDomain.SetData("APP_CONFIG_FILE", configPath)

EDIT: Actually looks like this is more complicated within a compiled exe - you need to do something like this in order to get the config reloaded.