BoundaryMeshRegionQ
BoundaryMeshRegionQ[reg] yields True if the region reg is a valid BoundaryMeshRegion object and False otherwise.
Examples
Test if region is a boundary mesh:
reg = BoundaryMeshRegion[{{0, 0}, {1, 0}, {0, 1}}, Line[{1, 2, 3, 1}]];
BoundaryMeshRegionQ[reg]
(* True *)Please visit the official Wolfram Language Reference for more details.