diff --git a/tests/unit/mathService.test.ts b/tests/unit/mathService.test.ts
index 6967a33..eac781c 100644
--- a/tests/unit/mathService.test.ts
+++ b/tests/unit/mathService.test.ts
@@ -9,4 +9,11 @@ describe("Math Service - add", () => {
         const result = math.add(1, 2)
         expect(result).toBe(3)
     })
+
+    it("should throw an error if any of the arguments is not a number", () => {
+        expect(() => math.add(1, "2" as any)).toThrow("Both arguments must be numbers")
+        expect(() => math.add("1" as any, 2)).toThrow("Both arguments must be numbers")
+        expect(() => math.add("1" as any, "2" as any)).toThrow("Both arguments must be numbers")
+        expect(() => math.add(1, null as any)).toThrow("Both arguments must be numbers")
+    })
 })