diff --git a/test/test_addition.c b/test/test_addition.c
index 89ddcd2..0d97725 100644
--- a/test/test_addition.c
+++ b/test/test_addition.c
@@ -133,6 +133,24 @@ void test_addition_addition_allunsignedinteger(void)
     TEST_ASSERT_EQUAL_UINT(expected[4], result[4]);
 }
 
+void test_addition_signnumber(void) {
+    unsigned int result[2];
+    unsigned int expected[2] = { 0, 1 };
+    union {
+        float f;
+        unsigned int i;
+    }a;
+
+    a.f = 1;
+    result[0] = s(a.i);
+
+    a.f = -1;
+    result[1] = s(a.i);
+
+    TEST_ASSERT_EQUAL_UINT(expected[0], result[0]);
+    TEST_ASSERT_EQUAL_UINT(expected[1], result[1]);
+}
+
 void test_addition_addition_float_0plus0gleich0(void) {
     float result;
     float expected = 0.0;