diff --git a/src/stlProcess.jl b/src/stlProcess.jl
index b286539..1d036c3 100644
--- a/src/stlProcess.jl
+++ b/src/stlProcess.jl
@@ -74,7 +74,7 @@ function get_mass_properties(triangles; scale=1)
     inertia[2, 3] = inertia[3, 2] = -(intg[9] - volume .* center_of_gravity[2] .* center_of_gravity[3])
     inertia[1, 3] = inertia[3, 1] = -(intg[10] - volume .* center_of_gravity[3] .* center_of_gravity[1])
 
-    return Properties(volume, center_of_gravity, inertia)
+    return Properties(volume, center_of_gravity, inertia ./ volume)
 end
 
 function fast_volume(triangles; scale=1)
diff --git a/test/runtests.jl b/test/runtests.jl
index 17eed18..e9b9518 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,6 +1,7 @@
 using Test
 
 using stlProcess
+import stlProcess.Properties
 
 using FileIO
 using MeshIO
@@ -45,37 +46,41 @@ function _check_volume(triangles; scale=1)
     return volume
 end
 
-@testset "simple cube stl" begin
-    """
-    inertia math:
-        https://hepweb.ucsd.edu/ph110b/110b_notes/node26.html
+@testset "3D Models" begin
+    I_mat = Matrix(I, 3, 3)
+    center = [0, 0, 0]
 
-    Cube is a standard cube with a length of 2 for each side.
-    """
-    cube_path = raw"test_assets\cubeblender.stl"
-    stl = load(cube_path)
+    models = Dict(
+        # Inertia math: https://en.wikipedia.org/wiki/List_of_moments_of_inertia#List_of_3D_inertia_tensors
+        # Properties(volume, center_of_gravity, inertia)
+        "cube.stl" => Properties(2.0^3, center, I_mat .* 2^2 / 6), # l = 2
+        "sphere.stl" => Properties(4 / 3 * pi, center, I_mat .* 2 / 5), # r = 1
+        "2_4_8_cuboid.stl" => Properties(2 * 4 * 8, center, diagm([2^2 + 4^2, 8^2 + 2^2, 8^2 + 4^2]) ./ 12), # h, d, w = 2, 4, 8
+        "slender_y.stl" => Properties(10 * π * 0.1^2, center, diagm([1, 0, 1]) .* (10^2 / 12)), # l_z = 10, r = 0.1
+        "cylinder.stl" => Properties(10 * π * 1^2, center, diagm([(3 + 10^2) / 12, (3 + 10^2) / 12, 1^2 / 2])), # l_z = 10, r = 1
+    )
+    @testset "$model" for (model, control) in models
+        path = "test_assets\\$model"
+        stl = load(path)
 
-    @testset "get_mass_properties function" begin
-        props = get_mass_properties(stl)
+        @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 function" begin
-            @test _check_volume(stl; scale=1) ≈ props.volume rtol = 0.01
-            @test _check_volume(stl; scale=4) ≈ (4 * 2)^3 rtol = 0.01
+            @test props.volume ≈ control.volume atol = 0.5
+            @test props.center_of_gravity ≈ control.center_of_gravity atol = 0.01
+            @test eigvals(props.inertia) ≈ eigvals(control.inertia) atol = 0.1
+        end
+        @testset "Compare volumes with scaling" begin
+            for scale in 1:5
+                props = get_mass_properties(stl; scale=scale)
+                volume = _check_volume(stl; scale=scale)
+                @test props.volume ≈ volume atol = 0.1
+            end
+        end
+        @testset "find_volume" begin
+            for scale in [0.5, 1, 1.0, 10, 2 / 3]
+                @test fast_volume(stl; scale=find_scale(stl; desired_volume=scale)) ≈ scale
+            end
         end
     end
-    @testset "Compare volumes with scaling" begin
-        for scale in 1:5
-            props = get_mass_properties(stl; scale=scale)
-            volume = _check_volume(stl; scale=scale)
-
-            @test props.volume ≈ volume rtol = 0.01
-        end
-    end
-    @testset "Find Scale" begin
-        @test fast_volume(stl; scale=find_scale(stl)) == 1.0
-    end
-end
+end
\ No newline at end of file
diff --git a/test/test_assets/2_4_8_cuboid.stl b/test/test_assets/2_4_8_cuboid.stl
new file mode 100644
index 0000000..f07d1da
Binary files /dev/null and b/test/test_assets/2_4_8_cuboid.stl differ
diff --git a/test/test_assets/README.md b/test/test_assets/README.md
new file mode 100644
index 0000000..eaee96a
--- /dev/null
+++ b/test/test_assets/README.md
@@ -0,0 +1,27 @@
+# Test Assets
+
+## cube.stl
+
+Perfect cube with length of 2 for all sides and a center of gravity at origin.
+
+## 2_4_8_cuboid.stl
+
+Cube with dimensions:
+
+- height = 2
+- depth = 4
+- width = 8
+
+Center of gravity at origin.
+
+## sphere.stl
+
+Perfect sphere with radius of 1 and a center of gravity at origin.
+
+## slender_rod.stl
+
+Negligible thickness cylinder with length of 10, radius of 0.1, and a center of gravity at origin.
+
+## cylinder.stl
+
+Cylinder with length of 10, radius of 1, and a center of gravity at origin.
diff --git a/test/test_assets/cubeblender.stl b/test/test_assets/cube.stl
similarity index 100%
rename from test/test_assets/cubeblender.stl
rename to test/test_assets/cube.stl
diff --git a/test/test_assets/cylinder.stl b/test/test_assets/cylinder.stl
new file mode 100644
index 0000000..7a532b6
Binary files /dev/null and b/test/test_assets/cylinder.stl differ
diff --git a/test/test_assets/slender_y.stl b/test/test_assets/slender_y.stl
new file mode 100644
index 0000000..a755235
Binary files /dev/null and b/test/test_assets/slender_y.stl differ
diff --git a/test/test_assets/sphere.stl b/test/test_assets/sphere.stl
new file mode 100644
index 0000000..6af6f2b
Binary files /dev/null and b/test/test_assets/sphere.stl differ