From 3f82a320f9d930939bf6057fd73fee992792d8ac Mon Sep 17 00:00:00 2001
From: Vinzent Steinberg <Vinzent.Steinberg@gmail.com>
Date: Thu, 25 Apr 2019 14:49:23 +0200
Subject: [PATCH] Use proptest to test reasonable bounds of mean

---
 Cargo.toml        |  1 +
 tests/proptest.rs | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 tests/proptest.rs

diff --git a/Cargo.toml b/Cargo.toml
index fb460f0..a4cf210 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -43,3 +43,4 @@ rand = "0.6"
 serde_json = "1"
 streaming-stats = "0.2"
 quantiles = "0.7"
+proptest = "0.9"
diff --git a/tests/proptest.rs b/tests/proptest.rs
new file mode 100644
index 0000000..4a28e2c
--- /dev/null
+++ b/tests/proptest.rs
@@ -0,0 +1,28 @@
+#![cfg_attr(feature = "cargo-clippy", allow(float_cmp, map_clone))]
+
+#[macro_use] extern crate average;
+#[macro_use] extern crate proptest;
+
+extern crate core;
+
+use core::iter::Iterator;
+
+use average::Mean;
+use proptest::prelude::*;
+use prop::num::f64;
+
+proptest! {
+    #![proptest_config(ProptestConfig::with_cases(10000))]
+    #[test]
+    fn reasonable_bounds(s in prop::collection::vec(
+        f64::POSITIVE | f64::NEGATIVE | f64::SUBNORMAL | f64::ZERO, 1..100usize)) {
+        // See https://hypothesis.works/articles/calculating-the-mean/.
+        let max = s.iter().cloned().fold(0./0., f64::max);
+        let min = s.iter().cloned().fold(0./0., f64::min);
+        let a: Mean = s.iter().collect();
+        let mean = a.mean();
+        println!("min: {}  mean: {}  max: {}", min, mean, max);
+        assert!(min <= mean);
+        assert!(mean <= max);
+    }
+}