diff --git a/spec/vec3_spec.lua b/spec/vec3_spec.lua
index 7db88b5..d620eca 100644
--- a/spec/vec3_spec.lua
+++ b/spec/vec3_spec.lua
@@ -225,9 +225,29 @@ describe("vec3:", function()
 		assert.is.equal(temp, vec3(-1, -2, -3))
 	end)
 
-	-- it("get two 3-vectors angle", function()
-	-- 	local a = vec3(1,2,3)
-	-- 	local b = vec3(3,2,1)
-	-- 	-- assert.is.equal(a:angle_to(b), 1)
-	-- end)
+	it("get two 3-vectors angle", function()
+    local angle_to = function(a, b)
+      local deg = math.deg(a:angle_to(b))
+      return string.format('%.2f', deg)
+    end
+		local a = vec3(1,2,3)
+		assert.is.equal(angle_to(a, vec3(3, 2, 1)), '44.42')
+    assert.is.equal(angle_to(a, vec3(0, 10, 0)), '57.69')
+    assert.is.equal(angle_to(a, vec3(0, -12, -10)), '157.51')
+
+    a = vec3.unit_z
+    assert.is.equal(angle_to(a, vec3(0, 10, 0)), '90.00')
+		assert.is.equal(angle_to(a, vec3(-123, 10, 0)), '90.00')
+		assert.is.equal(angle_to(a, vec3(-10, 0, 10)), '45.00')
+		assert.is.equal(angle_to(a, vec3(-10, 0, -10)), '135.00')
+		assert.is.equal(angle_to(a, vec3(0, -10, -10)), '135.00')
+		assert.is.equal(angle_to(a, vec3(0, 0, -10)), '180.00')
+		assert.is.equal(angle_to(a, vec3(0, 0, 100)), '0.00')
+
+    a = vec3(100, 100, 0)
+		assert.is.equal(angle_to(a, vec3(0, 0, 100)), '90.00')
+		assert.is.equal(angle_to(a, vec3(0, 0, -100)), '90.00')
+		assert.is.equal(angle_to(a, vec3(-10, -10, 0)), '180.00')
+		assert.is.equal(angle_to(a, vec3.unit_z), '90.00')
+	end)
 end)