cuprated: config versioning + backwards compat test (#394)

* apply

* typo

* fix path

binaries/cuprated/config/Cuprated.toml

@@ -0,0 +1 @@
+0.0.1.toml

binaries/cuprated/config/README.md

@@ -0,0 +1,6 @@
+# `cuprated` configs
+This directory holds configuration files for all `cuprated` versions.
+
+For example, `0.0.1.toml` is the config file for `cuprated v0.0.1`.
+
+`Cuprated.toml` is a symlink to the latest config file.

binaries/cuprated/src/config.rs

@@ -177,3 +177,35 @@ impl Config {
         self.p2p.block_downloader.clone().into()
     }
 }
+
+#[cfg(test)]
+mod test {
+    use toml::from_str;
+
+    use crate::constants::EXAMPLE_CONFIG;
+
+    use super::*;
+
+    /// Tests the latest config is the `Default`.
+    #[test]
+    fn config_latest() {
+        let config: Config = from_str(EXAMPLE_CONFIG).unwrap();
+        assert_eq!(config, Config::default());
+    }
+
+    /// Tests backwards compatibility.
+    #[test]
+    fn config_backwards_compat() {
+        // (De)serialization tests.
+        #[expect(
+            clippy::single_element_loop,
+            reason = "Remove after adding other versions"
+        )]
+        for version in ["0.0.1"] {
+            let path = format!("config/{version}.toml");
+            println!("Testing config serde backwards compat: {path}");
+            let string = read_to_string(path).unwrap();
+            from_str::<Config>(&string).unwrap();
+        }
+    }
+}

binaries/cuprated/src/constants.rs

@@ -23,7 +23,7 @@ pub const VERSION_BUILD: &str = formatcp!("{VERSION}-{}", cuprate_constants::bui
 pub const PANIC_CRITICAL_SERVICE_ERROR: &str =
     "A service critical to Cuprate's function returned an unexpected error.";
 
-pub const EXAMPLE_CONFIG: &str = include_str!("../Cuprated.toml");
+pub const EXAMPLE_CONFIG: &str = include_str!("../config/Cuprated.toml");
 
 #[cfg(test)]
 mod test {
@@ -45,11 +45,4 @@ mod test {
             assert_eq!(VERSION_BUILD, "0.0.1-release");
         }
     }
-
-    #[test]
-    fn generate_config_text_is_valid() {
-        let config: Config = toml::from_str(EXAMPLE_CONFIG).unwrap();
-
-        assert_eq!(config, Config::default());
-    }
 }