public void GetConnectors_Returns_ConnectorCollection()
        {
            // Arrange.
            var expression = new OneInTwoOutExpression();

            // Act.
            var connectors = expression.GetConnectors().ToList();

            // Assert.
            Assert.AreEqual(3, connectors.Count);
            Assert.IsTrue(connectors.Contains(expression.ConnectorIn));
            Assert.IsTrue(connectors.Contains(expression.Connector1Out));
            Assert.IsTrue(connectors.Contains(expression.Connector2Out));
        }