public void PerceptronThrowsErrorWhenWeightsAreAllZero() { _network.GetAllConnections().Enumerate(connection => connection.Properties.Weight = 0d); //Note: NullReferenceException means exception wasn't thrown var exception = Assert.Throws <InvalidOperationException>(() => _perceptron.CheckTopology()); exception.Message.Should().Be(Perceptron.WeightsAreAllZero); }