Add Euclidean label assignment regression test

Author: neuralsorcerer

src/kmeans.rs

@@ -672,10 +672,33 @@ pub fn minibatch_fit(
 
 #[cfg(test)]
 mod tests {
-    use super::{MiniBatchState, minibatch_partial_fit};
+    use super::{MiniBatchState, assign_labels, minibatch_partial_fit};
     use crate::errors::ClustorError;
     use crate::metrics::Metric;
 
+    #[test]
+    fn assign_labels_euclidean_assigns_each_sample_independently() {
+        let data = vec![0.0, 0.0, 9.0, 9.0];
+        let centers = vec![0.0, 0.0, 10.0, 10.0];
+        let mut labels = vec![usize::MAX; 2];
+
+        let inertia = assign_labels(
+            &data,
+            None,
+            &centers,
+            None,
+            None,
+            2,
+            2,
+            2,
+            Metric::Euclidean,
+            &mut labels,
+        );
+
+        assert_eq!(labels, vec![0, 1]);
+        assert!((inertia - 2.0).abs() < 1e-12);
+    }
+
     #[test]
     fn minibatch_partial_fit_keeps_cosine_norms_in_sync_with_center_updates() {
         let mut state = MiniBatchState {

src/metrics.rs

@@ -12,10 +12,13 @@ pub enum Metric {
 
 impl Metric {
     pub fn parse(s: &str) -> Option<Self> {
-        match s.to_ascii_lowercase().as_str() {
-            "euclidean" | "l2" => Some(Metric::Euclidean),
-            "cosine" => Some(Metric::Cosine),
-            _ => None,
+        let bytes = s.as_bytes();
+        if bytes.eq_ignore_ascii_case(b"l2") || bytes.eq_ignore_ascii_case(b"euclidean") {
+            Some(Metric::Euclidean)
+        } else if bytes.eq_ignore_ascii_case(b"cosine") {
+            Some(Metric::Cosine)
+        } else {
+            None
         }
     }
 }
@@ -91,7 +94,26 @@ pub fn normalize_in_place(v: &mut [f64]) {
 
 #[cfg(test)]
 mod tests {
-    use super::cosine_distance;
+    use super::{Metric, cosine_distance};
+
+    #[test]
+    fn metric_parse_accepts_aliases_case_insensitively() {
+        assert_eq!(Metric::parse("EUCLIDEAN"), Some(Metric::Euclidean));
+        assert_eq!(Metric::parse("L2"), Some(Metric::Euclidean));
+        assert_eq!(Metric::parse("CoSiNe"), Some(Metric::Cosine));
+    }
+
+    #[test]
+    fn metric_parse_rejects_unknown_values() {
+        assert_eq!(Metric::parse("manhattan"), None);
+        assert_eq!(Metric::parse(""), None);
+        assert_eq!(Metric::parse(" euclidean"), None);
+    }
+
+    #[test]
+    fn metric_parse_rejects_non_ascii_confusables() {
+        assert_eq!(Metric::parse("cоsine"), None); // Cyrillic small o
+    }
 
     #[test]
     fn cosine_distance_handles_zero_vectors() {