public void SignatureReader_ReadsRandomData_ThrowsException() { // Arrange var signatureData = new byte[1458]; new Random().NextBytes(signatureData); var signatureStream = new MemoryStream(signatureData); var progressReporter = Substitute.For <IProgress <ProgressReport> >(); // Act var target = new SignatureReader(signatureStream, progressReporter); // Assert Assert.Throws <InvalidDataException>(() => target.ReadSignature()); }