Write test case for lines that extend (or lie entirely) outside of raster grid area.
Expected behaviour: If a line is entirely outside the grid area, return the line unchanged (perhaps behaviour modifiable by flag). If a line is partly outside the grid area, split the line within the grid.
Write test case for lines that extend (or lie entirely) outside of raster grid area.
Expected behaviour: If a line is entirely outside the grid area, return the line unchanged (perhaps behaviour modifiable by flag). If a line is partly outside the grid area, split the line within the grid.