test: verify path_of normal behaviour

src/tests/fs.rs

@@ -15,6 +15,18 @@ mod path_of {
 
         Ok(())
     }
+
+   #[test]
+   fn matches_joins() -> TestResult {
+       let fs = fs::temp()?;
+
+       let joined = fs.base().join("foo").join("bar");
+       let path_of = fs.path_of("foo/bar".into())?;
+
+       assert_eq!(joined, path_of);
+
+       Ok(()) 
+    } 
 }
 
 mod file {