public TrackingPointMock(ITextBuffer textBuffer, int position, PointTrackingMode trackingMode, TrackingFidelityMode trackingFidelity)
 {
     _position = position;
     
     TextBuffer = textBuffer;
     TrackingFidelity = trackingFidelity;
     TrackingMode = trackingMode;
 }

		public MappingPoint(IBufferGraph bufferGraph, SnapshotPoint snapshotPoint, PointTrackingMode trackingMode) {
			if (bufferGraph == null)
				throw new ArgumentNullException(nameof(bufferGraph));
			if (snapshotPoint.Snapshot == null)
				throw new ArgumentException();
			BufferGraph = bufferGraph;
			this.snapshotPoint = snapshotPoint;
			this.trackingMode = trackingMode;
		}

		public TrackingPoint(ITextVersion textVersion, int position, PointTrackingMode trackingMode, TrackingFidelityMode trackingFidelity) {
			if (textVersion == null)
				throw new ArgumentNullException(nameof(textVersion));
			if ((uint)position > (uint)textVersion.Length)
				throw new ArgumentOutOfRangeException(nameof(position));
			TextBuffer = textVersion.TextBuffer;
			TrackingMode = trackingMode;
			TrackingFidelity = trackingFidelity;
			this.textVersion = textVersion;
			this.position = position;
		}

		public SnapshotPoint? MapDownToSnapshot(SnapshotPoint position, PointTrackingMode trackingMode, ITextSnapshot targetSnapshot, PositionAffinity affinity) {
			if (position.Snapshot == null)
				throw new ArgumentException();
			if (targetSnapshot == null)
				throw new ArgumentNullException(nameof(targetSnapshot));

			var res = MapDownToBuffer(position, trackingMode, targetSnapshot.TextBuffer, affinity);
			if (res == null)
				return null;
			return res.Value.TranslateTo(targetSnapshot, trackingMode);
		}

		public SnapshotPoint? MapDownToBuffer(SnapshotPoint position, PointTrackingMode trackingMode, ITextBuffer targetBuffer, PositionAffinity affinity) {
			if (position.Snapshot == null)
				throw new ArgumentException();
			if (targetBuffer == null)
				throw new ArgumentNullException(nameof(targetBuffer));

			if (position.Snapshot.TextBuffer != TopBuffer)
				return null;
			if (TopBuffer != targetBuffer)
				return null;
			return position.TranslateTo(targetBuffer.CurrentSnapshot, trackingMode);
		}

 public SnapshotPoint? MapDownToInsertionPoint(SnapshotPoint position, PointTrackingMode trackingMode, Predicate<ITextSnapshot> match) {
     var snapshot = position.Snapshot;
     var buffer = snapshot.TextBuffer;
     int pos = position.TranslateTo(snapshot, trackingMode);
     while (!match(snapshot)) {
         var projBuffer = buffer as IProjectionBufferBase;
         if (projBuffer == null) {
             return null;
         }
         var projSnapshot = projBuffer.CurrentSnapshot;
         if (projSnapshot.SourceSnapshots.Count == 0) {
             return null;
         }
         var pt = projSnapshot.MapToSourceSnapshot(pos);
         pos = pt.Position;
         snapshot = pt.Snapshot;
         buffer = snapshot.TextBuffer;
     }
     return new SnapshotPoint(snapshot, pos);
 }

 public ITrackingPoint CreateTrackingPoint(int position, PointTrackingMode trackingMode, TrackingFidelityMode trackingFidelity)
 {
     throw new NotImplementedException();
 }

 public ReplSpan WithEndTrackingMode(PointTrackingMode endTrackingMode)
 {
     return new ReplSpan(((CustomTrackingSpan)this.Span).WithEndTrackingMode(endTrackingMode), this.Kind);
 }

 public SnapshotPoint? MapUpToBuffer(SnapshotPoint point, PointTrackingMode trackingMode, PositionAffinity affinity, ITextBuffer targetBuffer) {
     return point;
 }

		public ITrackingPoint CreateTrackingPoint(int position, PointTrackingMode trackingMode, TrackingFidelityMode trackingFidelity) =>
			Version.CreateTrackingPoint(position, trackingMode, trackingFidelity);

 public SnapshotPoint? MapDownToBuffer(SnapshotPoint position, PointTrackingMode trackingMode, ITextBuffer targetBuffer, PositionAffinity affinity) {
     throw new NotImplementedException();
 }

 public SnapshotPoint? MapDownToInsertionPoint(SnapshotPoint position, PointTrackingMode trackingMode, Predicate<ITextSnapshot> match) {
     throw new NotImplementedException();
 }

 public SnapshotPoint? MapUpToBuffer(SnapshotPoint point, PointTrackingMode trackingMode, PositionAffinity affinity, ITextBuffer targetBuffer) {
     int position = 0;
     for (int i = 0; i < _buffers.Count; i++) {
         if (_buffers[i] == targetBuffer) {
             return new SnapshotPoint(point.Snapshot, position + point.Position);
         }
         position += _buffers[i].CurrentSnapshot.Length;
     }
     return null;
 }

		public SnapshotPoint? MapDownToFirstMatch(SnapshotPoint position, PointTrackingMode trackingMode, Predicate<ITextSnapshot> match, PositionAffinity affinity) {
			if (position.Snapshot == null)
				throw new ArgumentException();
			if (match == null)
				throw new ArgumentNullException(nameof(match));

			if (position.Snapshot.TextBuffer != TopBuffer)
				return null;
			if (!match(TopBuffer.CurrentSnapshot))
				return null;
			return position.TranslateTo(TopBuffer.CurrentSnapshot, trackingMode);
		}

		public IMappingPoint CreateMappingPoint(SnapshotPoint point, PointTrackingMode trackingMode) {
			if (point.Snapshot == null)
				throw new ArgumentException();
			return new MappingPoint(this, point, trackingMode);
		}

 public SnapshotPoint GetNearestPointInVisualSnapshot(SnapshotPoint editBufferPoint, ITextSnapshot targetVisualSnapshot, PointTrackingMode trackingMode) {
     throw new NotImplementedException();
 }

 public ITrackingPoint CreateTrackingPoint(int position, PointTrackingMode trackingMode) {
     return new MockTrackingPoint(this, position);
 }

 public SnapshotPoint? MapUpToSnapshot(SnapshotPoint point, PointTrackingMode trackingMode, PositionAffinity affinity, ITextSnapshot targetSnapshot) {
     throw new NotImplementedException();
 }

 public ITrackingPoint CreateTrackingPoint(int position, PointTrackingMode trackingMode)
 {
     return TextBuffer.CurrentSnapshot.CreateTrackingPoint(position, trackingMode);
 }

 public SnapshotPoint? MapUpToSnapshot(SnapshotPoint point, PointTrackingMode trackingMode, PositionAffinity affinity, ITextSnapshot targetSnapshot) {
     return point;
 }