Add proptest for integral function

Cargo.toml

@@ -17,4 +17,5 @@ anyhow = "1"
 thiserror = "1"
 
 [dev-dependencies]
+proptest = "1.4"
 tokio = { version = "1", features = ["full"] }

src/lib.rs

@@ -171,4 +171,15 @@ mod tests {
 
  Ok(())
  }
+
+ use proptest::prelude::*;
+ proptest! {
+ #![proptest_config(ProptestConfig::with_cases(100000))]
+ #[test]
+ fn test_integral(mu: f64, sigma: f64, x: f64) {
+ let dist = NormalDist { mu, sigma };
+ let y = dist.integral(x);
+ assert!(0. <= y && y <= 1.);
+ }
+ }
 }