diff --git a/src/conversions/sample_rate.rs b/src/conversions/sample_rate.rs
index 3ad3cd3..9e1e41e 100644
--- a/src/conversions/sample_rate.rs
+++ b/src/conversions/sample_rate.rs
@@ -372,6 +372,8 @@ mod test {
         let input = vec![2u16, 16, 4, 18, 6, 20, 8, 22];
         let output =
             SampleRateConverter::new(input.into_iter(), SampleRate(2000), SampleRate(3000), 2);
+        assert_eq!(output.len(), 12); // Test the source's Iterator::size_hint()
+
         let output = output.collect::<Vec<_>>();
         assert_eq!(output, [2, 16, 3, 17, 4, 18, 6, 20, 7, 21, 8, 22]);
     }
@@ -381,7 +383,9 @@ mod test {
         let input = vec![1u16, 14];
         let output =
             SampleRateConverter::new(input.into_iter(), SampleRate(1000), SampleRate(7000), 1);
+        let size_estimation = output.len();
         let output = output.collect::<Vec<_>>();
         assert_eq!(output, [1, 2, 4, 6, 8, 10, 12, 14]);
+        assert!((size_estimation as f32 / output.len() as f32).abs() < 2.0);
     }
 }