Update test to use assert_ulps_eq

src/lib.rs

@@ -79,6 +79,15 @@ where
     }
 }
 
+impl<K> Default for IndexMap<K>
+where
+    K: Eq + Hash,
+{
+    fn default() -> Self {
+        IndexMap::new()
+    }
+}
+
 fn erfc(x: f64) -> f64 {
     let z = x.abs();
     let t = 1.0 / (1.0 + z / 2.0);