extern crate rand;
extern crate wasm_bindgen;
extern crate wasm_bindgen_test;

use rand::rngs::StdRng;
use rand::Rng;
use rand::SeedableRng;
use wasm_bindgen::prelude::*;
use wasm_bindgen_test::*;

#[wasm_bindgen]
pub fn generate_from_seed(seed: u32) -> u32 {
    StdRng::seed_from_u64(seed as u64).gen()
}

pub mod tests {
    use super::*;

    #[wasm_bindgen_test]
    fn generate_from_seed_test() {
        let _ = generate_from_seed(42);
    }
}

extern crate rand;
extern crate wasm_bindgen;
extern crate wasm_bindgen_test;

use rand::rngs::StdRng;
use rand::Rng;
use rand::SeedableRng;
use wasm_bindgen::prelude::*;
use wasm_bindgen_test::*;

#[wasm_bindgen]
pub fn generate_from_seed(seed: u64) -> u64 {
    StdRng::seed_from_u64(seed).gen()
}

pub mod tests {
    use super::*;

    #[wasm_bindgen_test]
    fn generate_from_seed_test() {
        let _ = generate_from_seed(42);
    }
}

--- 
+++ 
@@ -9,8 +9,8 @@
 use wasm_bindgen_test::*;
 
 #[wasm_bindgen]
-pub fn generate_from_seed(seed: u64) -> u64 {
-    StdRng::seed_from_u64(seed).gen()
+pub fn generate_from_seed(seed: u32) -> u32 {
+    StdRng::seed_from_u64(seed as u64).gen()
 }
 
 pub mod tests {
Use u32 instead of u64 in wasm_bindgen test interface
