diff --git a/src/lib.rs b/src/lib.rs
index 56f5907..33ecfa4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -320,6 +320,8 @@ pub fn quality(rating_groups: &[&[Gaussian]], beta: f64) -> f64 {
 
 #[cfg(test)]
 mod tests {
+    use ::approx::assert_ulps_eq;
+
     use super::*;
 
     #[test]
@@ -331,4 +333,14 @@ mod tests {
     fn test_sort_time() {
         assert_eq!(sort_time(&[0, 1, 2, 0], true), vec![2, 1, 0, 3]);
     }
+
+    #[test]
+    fn test_quality() {
+        let a = Gaussian::from_ms(25.0, 3.0);
+        let b = Gaussian::from_ms(25.0, 3.0);
+
+        let q = quality(&[&[a], &[b]], 25.0 / 3.0 / 2.0);
+
+        assert_ulps_eq!(q, 0.8115343414514944, epsilon = 1e-6)
+    }
 }