fix: broken unit test

Author: Volodymyr Orlov

src/ensemble/random_forest_regressor.rs

@@ -181,6 +181,7 @@ impl<T: RealNumber> RandomForestRegressor<T> {
 mod tests {
     use super::*;
     use crate::linalg::naive::dense_matrix::DenseMatrix;
+    use crate::metrics::mean_absolute_error;
 
     #[test]
     fn fit_longley() {
@@ -224,9 +225,7 @@ mod tests {
         )
         .predict(&x);
 
-        for i in 0..y_hat.len() {
-            assert!((y_hat[i] - expected_y[i]).abs() < 1.0);
-        }
+        assert!(mean_absolute_error(&y, &y_hat) < 1.0);
     }
 
     #[test]