added function to find volume

test/runtests.jl

@@ -8,12 +8,25 @@ using MeshIO
 using LinearAlgebra
 
 @testset "simple cube stl" begin
-    # https://hepweb.ucsd.edu/ph110b/110b_notes/node26.html
-    stl = load(raw"test\test_assets\cubeblender.stl")
+    """
+    inertia math:
+        https://hepweb.ucsd.edu/ph110b/110b_notes/node26.html
 
-    props = get_mass_properties(stl)
+    Cube is a standard cube with a length of 2 for each side.
+    """
+    cube_path = raw"test_assets\cubeblender.stl"
+    stl = load(cube_path)
 
-    @test props.volume == 8.0
-    @test all(props.center_of_gravity .== 0.0)
-    @test all(eigvals(props.inertia) .≈ (5.0 + 1 / 3))
+    @testset "get_mass_properties" begin
+        props = get_mass_properties(stl)
+
+        @test props.volume == 8.0
+        @test all(props.center_of_gravity .== 0.0)
+        @test all(eigvals(props.inertia) .≈ (5.0 + 1 / 3))
+
+        @testset "get_volume" begin
+            @test get_volume(stl; scale=1) ≈ props.volume rtol = 0.01
+            @test get_volume(stl; scale=4) ≈ (4 * 2)^3 rtol = 0.01
+        end
+    end
 end