[wip] unit testing

- styling, `test_util::make_check_trait_panic`

src/file/chunk.rs

@@ -112,7 +112,7 @@ mod tests {
     }
 
     #[test]
-    #[should_panic(expected = "did not fit into \"u32\"")]
+    #[should_panic = "did not fit into \"u32\""]
     fn test_usize_overflow_panics() {
         // works
         assert_eq!(from_usize_or_panic::<u64>(usize::MAX), u64::MAX);

src/test_util/mod.rs

@@ -28,3 +28,9 @@ pub fn create_file(data: &[u8]) -> NamedTempFile {
     tmp.write_all(data).unwrap();
     tmp
 }
+
+#[test]
+#[should_panic = "`impl foo for bar` expected: 1, actual: 0"]
+fn make_check_trait_panic() {
+    check_trait(0, 1, "foo", "bar");
+}