Microsoft.SharePoint.Client.ServerUnauthorizedAccessException on test server but not in dev

I am trying to save a document in Sharepoint 2013 with the following code;

using (var context = new ClientContext(this.SharepointServer))
{
    // context.Credentials = CredentialCache.DefaultNetworkCredentials;

    var list = context.Web.Lists.GetByTitle(this.DocumentLibrary);
    var fileCreationInformation = new FileCreationInformation
                                      {
                                          Content = file,
                                          Overwrite = true,
                                          Url = fileName
                                      };
    var uploadFile = list.RootFolder.Files.Add(fileCreationInformation);
    var listItem = uploadFile.ListItemAllFields;
    listItem.Update();
    try
    {
        context.ExecuteQuery();
    }
    catch (System.Exception ex)
    {
        throw ex;
    }

    if (this.Metadata.Count > 0)
    {
        this.SaveMetadata(uploadFile, context);
    }

    return GetSharepointFileInfo(context, list, uploadFile);
}

This throws an exception when running on the test server, but works on my local machine. I am using Windows Authentication. It may be that the application pool on the test server is running on a different account. However I can't see how to impersonate myself in order to save the document under my account. From what I can tell I need my password which is not available under windows authentication. So how do I fix this?