public void CreateTracer_Returns_Tracing_Formatter(MediaTypeFormatter formatter) { // Arrange HttpRequestMessage request = new HttpRequestMessage(); // Act MediaTypeFormatter tracingFormatter = MediaTypeFormatterTracer.CreateTracer(formatter, new TestTraceWriter(), request); // Assert IFormatterTracer tracer = Assert.IsAssignableFrom <IFormatterTracer>(tracingFormatter); Assert.Same(formatter, tracer.InnerFormatter); }