Programmatically configuring log4net

Question

I'm having the worst time trying to configure log4net properly. First, I need to give some background about how I've been using it so far (and successfully).

My application has a log4net configuration file that defines the FileAppender that it should log all data to. All of my assemblies have an ILog member variable, and set it to LogManager.GetLogger( typeof( myclass)), where myclass is the class that is logging.

Everything works great like this.

Now I also have an assembly that is used slightly differently. It can be instantiated multiple times, and the requirement is that each instance logs to its own file. I was able to get this to work programmatically, and ditching the logging.xml file.

        Hierarchy hierarchy = (Hierarchy)LogManager.GetRepository();
        hierarchy.Root.Level = log4net.Core.Level.All;            
        hierarchy.Configured = true;

        string module_path = MyCompany.Shared.Utils.FileSystem.GetModulePath();
        string folder = module_path + "\\logs\\";
        string path = String.Format("{0}{1}-log.txt", folder, name);

        _log = LogManager.GetLogger( name);

        var fa = new log4net.Appender.FileAppender() { Name = name, File = path, AppendToFile = true};
        var layout = new PatternLayout { ConversionPattern = "%date{{yyyy-MM-dd-HH_mm_ss.fff}} [%thread] %-5level %logger - %message%newline" };
        layout.ActivateOptions();
        fa.Layout = layout;
        fa.ActivateOptions();

        ((Logger)_log.Logger).AddAppender( fa);

This also works great. Now here's where the problem comes in: the above assembly uses another assembly that also uses log4net. However, that assembly is expecting there to be a logger already configured for use, and apparently the way I'm setting up log4net programmatically is preventing that from working.

I have enabled internal log4net debugging, and the error message I see is pretty explicit about the error, but I'm not sure how to (best) solve the problem:

log4net: Logger: No appenders could be found for logger [test_logger] repository [log4net-default-repository]
log4net: Logger: Please initialize the log4net system properly.
log4net: Logger:    Current AppDomain context information: 
log4net: Logger:       BaseDirectory   : C:\Sample\bin\Debug\
log4net: Logger:       FriendlyName    : SampleTestApp.vshost.exe
log4net: Logger:       DynamicDirectory: 
log4net: Hierarchy: Shutdown called on Hierarchy [log4net-default-repository]

I assume that the logger is created, since I get the same error even if I explicitly use the LoggerFactory to create a "test_logger" logger. So it's just a matter of figuring out how to create the appender for that logger. I have tried to use the previous code to create a FileAppender for this logger, but even though the code runs, I get the same error.

Can anyone suggest things for me to try to get this to work?

EDIT -- I should clarify that I really would like all of the log messages to go into the FileAppender that was created by the test app. I would like to avoid having separate files (one for each assembly).