diff --git a/hawk/t/t-006.c b/hawk/t/t-006.c
index 1ae32285..a41fc5dc 100644
--- a/hawk/t/t-006.c
+++ b/hawk/t/t-006.c
@@ -6,22 +6,51 @@
 
 struct
 {
-	hawk_ntime_sec_t s1;
+	hawk_ntime_sec_t s1;   /* input x */
 	hawk_ntime_nsec_t ns1;
-	hawk_ntime_sec_t s2;
+
+	hawk_ntime_sec_t s2;   /* input y */
 	hawk_ntime_nsec_t ns2;
 
-	hawk_ntime_sec_t add_s;
+	hawk_ntime_sec_t add_s; /* expected z after addition */
 	hawk_ntime_nsec_t add_ns;
-	hawk_ntime_sec_t sub_s;
+
+	hawk_ntime_sec_t sub_s;  /* expected z after subtraction */
 	hawk_ntime_nsec_t sub_ns;
 } tab[] = 
 {
+	/* 0 */
 	{ 12345678,  HAWK_NSECS_PER_SEC - 1,
 	  0,  10,
           12345679,  9,
           12345678,  HAWK_NSECS_PER_SEC - 11 },
 
+	{ 0,  0,
+	  12345678,  10,
+          12345678,  10,
+          -12345679,  HAWK_NSECS_PER_SEC - 10 },
+
+	{ 0,  0,
+	  -12345678,  10,
+          -12345678,  10,
+          12345677,  HAWK_NSECS_PER_SEC - 10 },
+
+	{ HAWK_TYPE_MAX(hawk_ntime_sec_t) - 1, HAWK_NSECS_PER_SEC - 1,
+	  1, 0,  
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), HAWK_NSECS_PER_SEC - 1, 
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t) - 2, HAWK_NSECS_PER_SEC - 1  },
+
+	{ HAWK_TYPE_MAX(hawk_ntime_sec_t) - 1, HAWK_NSECS_PER_SEC - 1,
+	  1, 1,
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), HAWK_NSECS_PER_SEC - 1, 
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t) - 2, HAWK_NSECS_PER_SEC - 2  },
+
+	/* 5 */
+	{ HAWK_TYPE_MAX(hawk_ntime_sec_t) - 1, HAWK_NSECS_PER_SEC - 1,
+	  1, 2,
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), HAWK_NSECS_PER_SEC - 1, 
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t) - 2, HAWK_NSECS_PER_SEC - 3  },
+
 	{ HAWK_TYPE_MAX(hawk_ntime_sec_t), 0,
 	  0, 0,  
 	  HAWK_TYPE_MAX(hawk_ntime_sec_t), 0, 
@@ -32,6 +61,22 @@ struct
 	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0, 
 	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0  },
 
+	{ HAWK_TYPE_MIN(hawk_ntime_sec_t) + 1, 0,
+	  1, 2,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t) + 2, 2,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0 },
+
+	{ HAWK_TYPE_MIN(hawk_ntime_sec_t) + 1, 0,
+	  2, 2,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t) + 3, 2,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0 },
+
+	/* 10 */
+	{ HAWK_TYPE_MIN(hawk_ntime_sec_t) + 1, 0,
+	  2, HAWK_NSECS_PER_SEC - 1,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t) + 3, HAWK_NSECS_PER_SEC - 1,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0 },
+
 	{ 0, 0,
 	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0, 
 	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0, 
@@ -45,18 +90,30 @@ struct
 	{ HAWK_TYPE_MAX(hawk_ntime_sec_t), 0,
 	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0,  
 	  -1, 0,
-	  HAWK_TYPE_MAX(hawk_ntime_sec_t), HAWK_NSECS_PER_SEC - 1  }
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), HAWK_NSECS_PER_SEC - 1  },
+
+	{ HAWK_TYPE_MIN(hawk_ntime_sec_t), 0,
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), 0,  
+	  -1, 0,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0 },
+
+	/* 15 */
+	{ HAWK_TYPE_MIN(hawk_ntime_sec_t), 0,
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), HAWK_NSECS_PER_SEC - 1,  
+	  -1, HAWK_NSECS_PER_SEC - 1,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0 }
 };
 
 int main ()
 {
 	hawk_ntime_t x, y, z;
 	int i;
-	char buf[64];
+	char buf1[64], buf2[64];
 
 	for (i = 0; i < HAWK_COUNTOF(tab); i++)
 	{
-		sprintf (buf, "test index %d", i);
+		sprintf (buf1, "add - index %d", i);
+		sprintf (buf2, "sub - index %d", i);
 
 		x.sec = tab[i].s1;
 		x.nsec = tab[i].ns1;
@@ -64,12 +121,12 @@ int main ()
 		y.nsec = tab[i].ns2;
 
 		hawk_add_ntime (&z, &x, &y);
-		T_ASSERT1 (z.sec == tab[i].add_s, buf);
-		T_ASSERT1 (z.nsec == tab[i].add_ns, buf);
+		T_ASSERT1 (z.sec == tab[i].add_s, buf1);
+		T_ASSERT1 (z.nsec == tab[i].add_ns, buf1);
 
 		hawk_sub_ntime (&z, &x, &y);
-		T_ASSERT1 (z.sec == tab[i].sub_s, buf);
-		T_ASSERT1 (z.nsec == tab[i].sub_ns, buf);
+		T_ASSERT1 (z.sec == tab[i].sub_s, buf2);
+		T_ASSERT1 (z.nsec == tab[i].sub_ns, buf2);
 
 	}