Add tests for SignedDuration

Author: wesleywiser

summarize/src/signed_duration.rs

@@ -67,3 +67,47 @@ impl fmt::Debug for SignedDuration {
         write!(f, "{:?}", self.duration)
     }
 }
+
+#[cfg(test)]
+mod test {
+    use std::time::Duration;
+    use super::SignedDuration;
+
+    #[test]
+    fn op_subtract() {
+        let zero_d = Duration::from_nanos(0);
+        let one_d = Duration::from_nanos(1);
+        let two_d = Duration::from_nanos(2);
+
+        let zero_sd = SignedDuration::from(zero_d);
+        let one_sd = SignedDuration::from(one_d);
+        let neg_one_sd = SignedDuration { duration: one_d, is_positive: false };
+        let two_sd = SignedDuration::from(two_d);
+        let neg_two_sd = SignedDuration { duration: two_d, is_positive: false };
+
+        assert_eq!(zero_d, zero_sd.duration);
+        assert_eq!(true, zero_sd.is_positive);
+
+        assert_eq!(zero_sd, zero_sd - zero_sd);
+
+        assert_eq!(one_d, one_sd.duration);
+        assert_eq!(true, one_sd.is_positive);
+
+        assert_eq!(one_sd, one_sd - zero_sd);
+
+        assert_eq!(one_d, neg_one_sd.duration);
+        assert_eq!(false, neg_one_sd.is_positive);
+
+        assert_eq!(neg_one_sd, neg_one_sd - zero_sd);
+
+        assert_eq!(zero_sd, one_sd - one_sd);
+
+        assert_eq!(one_sd, two_sd - one_sd);
+
+        assert_eq!(neg_one_sd, one_sd - two_sd);
+
+        assert_eq!(neg_two_sd, neg_one_sd - one_sd);
+
+        assert_eq!(zero_sd, neg_one_sd - neg_one_sd);
+    }
+}