diff --git a/test/test_addition.c b/test/test_addition.c
index 4190d62..ae4f1e7 100644
--- a/test/test_addition.c
+++ b/test/test_addition.c
@@ -13,6 +13,11 @@ union {
     unsigned int integer;
 } number[6];
 
+union {
+    double dnum;
+    unsigned long lnum;
+} numberd[6];
+
 void setUp(void)
 {
 }
@@ -279,4 +284,17 @@ void test_addition_addition_float_sumofpositivnumbers(void)
     TEST_ASSERT_EQUAL_FLOAT(expected[2], result[2]);
 }
 
+void test_addition_sign_double_numbers(void)
+{
+    unsigned long result[2];
+    unsigned long expected[2] = { 1, 0 };
+    numberd[0].dnum = -3004683105640520235, numberd[1].dnum = 0.05313546453135;
+    
+    result[0] = sign_double(numberd[0].lnum);
+    result[1] = sign_double(numberd[1].lnum);
+
+    TEST_ASSERT_EQUAL_UINT64(expected[0], result[0]);
+    TEST_ASSERT_EQUAL_UINT64(expected[1], result[1]);
+}
+
 #endif // TEST