public async Task CacheAsync(string subfolder)
{
// prepare
var fileName = Guid.NewGuid().ToString() + ".dat";
var cacher = new ImageCacher();
// act
var result = await cacher.CacheAsync(subfolder + fileName, GetSomeData);
// verify
Assert.EndsWith(fileName, result);
Assert.True(File.Exists(result));
using (var file = File.OpenRead(result))
using (var someData = GetSomeData())
Assert.Equal(await GetContentAsync(someData), await GetContentAsync(file));
}
