This is BRL-CAD's LIBBN basic numerics library.

The following functions are typically called (heavily) during geometry
facetization and would make for an excellent starting point for unit
tests:

bn_3pts_collinear
bn_3pts_distinct
bn_angle_measure
bn_dist_pt3_line3
bn_dist_pt3_lseg3
bn_dist_pt3_pt3
bn_distsq_line3_pt3
bn_distsq_pt3_lseg3
bn_isect_line3_line3
bn_isect_line3_plane
bn_isect_line_lseg
bn_isect_lseg3_lseg3
bn_isect_pt_lseg
bn_mat_arb_rot
bn_mat_determinant
bn_mat_fromto
bn_mat_inv
bn_mat_mul
bn_mk_plane_3pts
bn_mkpoint_3planes
bn_pt3_pt3_equal
bn_vec_ortho
bn_vec_perp