diff --git a/modules/engine-math/src/root.zig b/modules/engine-math/src/root.zig
index 265319ce..ad642c65 100644
--- a/modules/engine-math/src/root.zig
+++ b/modules/engine-math/src/root.zig
@@ -15,3 +15,4 @@ pub const utils = @import("utils.zig");
 pub const frustum_tests = @import("frustum_tests.zig");
 pub const mat4_tests = @import("mat4_tests.zig");
 pub const utils_tests = @import("utils_tests.zig");
+pub const voxel_tests = @import("voxel_tests.zig");
diff --git a/modules/engine-math/src/voxel_tests.zig b/modules/engine-math/src/voxel_tests.zig
new file mode 100644
index 00000000..bd19bb52
--- /dev/null
+++ b/modules/engine-math/src/voxel_tests.zig
@@ -0,0 +1,112 @@
+const std = @import("std");
+const testing = std.testing;
+const voxel = @import("voxel.zig");
+const Mat4 = @import("mat4.zig").Mat4;
+const Vec3 = @import("vec3.zig").Vec3;
+const Face = voxel.Face;
+
+test "Face.getShade returns correct values per face" {
+    try testing.expectApproxEqAbs(@as(f32, 1.0), Face.top.getShade(), 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0.5), Face.bottom.getShade(), 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0.8), Face.north.getShade(), 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0.8), Face.south.getShade(), 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0.7), Face.east.getShade(), 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0.7), Face.west.getShade(), 0.0001);
+}
+
+test "Face.getNormal returns correct normals" {
+    try testing.expectEqual([3]i8{ 0, 1, 0 }, Face.top.getNormal());
+    try testing.expectEqual([3]i8{ 0, -1, 0 }, Face.bottom.getNormal());
+    try testing.expectEqual([3]i8{ 0, 0, -1 }, Face.north.getNormal());
+    try testing.expectEqual([3]i8{ 0, 0, 1 }, Face.south.getNormal());
+    try testing.expectEqual([3]i8{ 1, 0, 0 }, Face.east.getNormal());
+    try testing.expectEqual([3]i8{ -1, 0, 0 }, Face.west.getNormal());
+}
+
+test "Face.getOffset returns integer offsets matching normals" {
+    try testing.expectEqual(Face.top.getOffset(), .{ .x = 0, .y = 1, .z = 0 });
+    try testing.expectEqual(Face.bottom.getOffset(), .{ .x = 0, .y = -1, .z = 0 });
+    try testing.expectEqual(Face.north.getOffset(), .{ .x = 0, .y = 0, .z = -1 });
+    try testing.expectEqual(Face.south.getOffset(), .{ .x = 0, .y = 0, .z = 1 });
+    try testing.expectEqual(Face.east.getOffset(), .{ .x = 1, .y = 0, .z = 0 });
+    try testing.expectEqual(Face.west.getOffset(), .{ .x = -1, .y = 0, .z = 0 });
+}
+
+test "ALL_FACES contains exactly six distinct faces" {
+    try testing.expectEqual(@as(usize, 6), voxel.ALL_FACES.len);
+    var seen = std.EnumArray(Face, bool).initEmpty();
+    for (voxel.ALL_FACES) |f| {
+        seen.set(f, true);
+    }
+    for (comptime std.enums.values(Face)) |f| {
+        try testing.expect(seen.get(f));
+    }
+}
+
+test "Mat4.multiply identity preserves matrix" {
+    const result = Mat4.multiply(Mat4.identity, Mat4.identity);
+    try testing.expectApproxEqAbs(@as(f32, 1), result.data[0][0], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 1), result.data[1][1], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 1), result.data[2][2], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 1), result.data[3][3], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[0][1], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[0][2], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[0][3], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[1][0], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[1][2], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[1][3], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[2][0], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[2][1], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[2][3], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[3][0], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[3][1], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), result.data[3][2], 0.0001);
+}
+
+test "Mat4.multiply translate then rotate produces correct transform" {
+    const translate = Mat4.translate(Vec3.init(5, 0, 0));
+    const rotate = Mat4.rotateY(std.math.pi / 2.0);
+    const combined = Mat4.multiply(rotate, translate);
+    const point = combined.transformPoint(Vec3.zero);
+    try testing.expectApproxEqAbs(@as(f32, 0), point.x, 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), point.y, 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, -5), point.z, 0.0001);
+}
+
+test "Mat4.transformPoint with w=1 does not divide" {
+    const m = Mat4.identity;
+    const result = m.transformPoint(Vec3.init(1, 2, 3));
+    try testing.expectApproxEqAbs(@as(f32, 1), result.x, 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 2), result.y, 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 3), result.z, 0.0001);
+}
+
+test "Mat4.inverse of singular matrix returns identity" {
+    const singular = Mat4.zero;
+    const inv = singular.inverse();
+    try testing.expectApproxEqAbs(@as(f32, 1), inv.data[0][0], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 1), inv.data[1][1], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 1), inv.data[2][2], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 1), inv.data[3][3], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[0][1], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[0][2], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[0][3], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[1][0], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[1][2], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[1][3], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[2][0], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[2][1], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[2][3], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[3][0], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[3][1], 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), inv.data[3][2], 0.0001);
+}
+
+test "Mat4.rotateY 90 degrees maps +X to -Z" {
+    const rot = Mat4.rotateY(std.math.pi / 2.0);
+    const v = Vec3.init(1, 0, 0);
+    const transformed = rot.transformDirection(v);
+    try testing.expectApproxEqAbs(@as(f32, 0), transformed.x, 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, 0), transformed.y, 0.0001);
+    try testing.expectApproxEqAbs(@as(f32, -1), transformed.z, 0.0001);
+}
diff --git a/src/tests.zig b/src/tests.zig
index f9c06fe8..c4bb6aaa 100644
--- a/src/tests.zig
+++ b/src/tests.zig
@@ -50,6 +50,7 @@ test {
     _ = @import("engine-graphics").shadow_tests;
     _ = @import("engine-shadows").shadow_system_tests;
     _ = @import("engine-math").utils_tests;
+    _ = @import("engine-math").voxel_tests;
     _ = @import("engine-math").frustum_tests;
     _ = @import("engine-math").mat4_tests;
     _ = @import("world-meshing").world_tests;