public void IsOnEdgeWhenStartAndFinishIsSamePoint()
        {
            var point = new PointD(0, 3);

            Assert.Throws <ArgumentException>(() => point.IsOnEdge(new PointD(0, 3), new PointD(0, 3)));
        }
        public void IsOnEdgeWhenStartBiggerThenFinish()
        {
            var point = new PointD(0, 3);

            Assert.True(point.IsOnEdge(new PointD(8, 3), new PointD(0, 3)));
        }
        public void IsOnEdgeWhenItIsRightPoint()
        {
            var point = new PointD(1, 0);

            Assert.True(point.IsOnEdge(new PointD(-1, 0), new PointD(1, 0)));
        }
        public void IsOnEdgeWhenItIsNotOnEdgeButOnLine()
        {
            var point = new PointD(5, 0);

            Assert.False(point.IsOnEdge(new PointD(-1, 0), new PointD(1, 0)));
        }
        public void IsOnEdgeWhenItIsOnMiddleOfLineSegment()
        {
            var point = new PointD(0, 0);

            Assert.True(point.IsOnEdge(new PointD(-1, 0), new PointD(1, 0)));
        }