public void TestAddExistingDocumentNumber() { _documentRepository.Setup(d => d.GetDocument(ExistingNumber)).Returns(document); IDocumentManager manager = new DocumentManager(_documentRepository.Object, null, null, null); Assert.That(() => manager.AddDocumentAsync(document), Throws.Exception.With.Property("Message") .EqualTo($"Документ с номером { document.Number} уже существует")); }