zcoord: plus_offset: Check both ways

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/base/zcoord.rs b/base/zcoord.rs
index 0f955f6c2e4ac4ed8fc4c174676cc836dba51438..b91333720d7e4bb9a707293afa645652ba1adc7c 100644 (file)
--- a/base/zcoord.rs
+++ b/base/zcoord.rs
@@ -967,12 +967,15 @@ mod test {
 
   #[test]
   fn plus_offset() {
-    let z: ZCoord = "3o00000000".parse().unwrap();
-    assert_eq!(z.plus_offset(0).unwrap(),
-               "3o00000000_0000004000".parse().unwrap());
-    assert_eq!(z.plus_offset(1).unwrap(),
-               "3o00000000_000000c000".parse().unwrap());
-    assert_eq!(z.plus_offset(0xffffffff).unwrap(),
-               "3o00000000_vvvvvvs000".parse().unwrap());
+    fn chk(off: u32, s: &str) {
+      let z: ZCoord = "3o00000000".parse().unwrap();
+      let p = z.plus_offset(off).unwrap();
+      assert_eq!(s, format!("{}", &p));
+      assert_eq!(p, s.parse().unwrap());
+    }
+
+    chk(         0, "3o00000000_0000004000");
+    chk(         1, "3o00000000_000000c000");
+    chk(0xffffffff, "3o00000000_vvvvvvs000");
   }
 }