Improve Unit Tests

[marip8]

Problems

• No real expectations on the results of the tool path planner in any test, just that a valid optional data type is returned
• Surface walk planner does not produce expected results (see #34)
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  • Non-deterministic results from surface walk planner(see #103, #47)
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• Eigen value edge path planner does not produce expected results
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• Extra rasters feature also produces (one?) extra waypoints
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Solutions

• [ ] Revise unit tests to use test fixtures to reduce code duplication
• [ ] Add meaningful expectations to the results of the tool path generation (e.g. number of strokes, number of points per stroke, normal direction
• [ ] Fix issues with surface walk and eigen value edge planners
• [ ] Transform test meshes by non-identity transformation to ensure results are correct and not just coincidentally correct (see #136)