为什么这个模块不可见?

我在用铁锈写一个散列码练习。代码如下所示:

pub fn get_fnv1a32(to_hash:&str) -> u32{
   const OFFSET_BASIS:u32 = 2_166_136_261;
   const PRIME:u32 = 16_777_619;

   if !to_hash.is_empty(){
      let mut hash = OFFSET_BASIS;
      for b in to_hash.bytes(){
         hash = hash ^ (b as u32);
         hash = hash.wrapping_mul(PRIME);
      }
      hash
   }
   else
   {
      0
   }
}

mod fnv;
#[cfg(test)]
mod tests {
    #[test]
    fn get_correct_hash(){
        assert_eq!(0x7a78f512, fnv::get_fnv1a32("Hello world!"));
    } 

    #[test]
    fn hash_handles_empty_string_correctly(){
        assert_eq!(0, fnv::get_fnv1a32(""));
    }
 } 

测试代码在lib.rs中,并且 get_fnv1a32 函数在fnv.rs中。它们都在同一目录中。但当我试着运行货物测试时,我不断收到以下信息:

Compiling hashes v0.1.0 (U:\skunkworks\rust\hashes)
warning: function is never used: `get_fnv1a32`
 --> src\fnv.rs:1:8
  |
1 | pub fn get_fnv1a32(to_hash:&str) -> u32{
  |        ^^^^^^^^^^^
  |
  = note: `#[warn(dead_code)]` on by default

error[E0433]: failed to resolve: use of undeclared type or module `fnv`
 --> src\lib.rs:7:32
  |
7 |         assert_eq!(0x7a78f512, fnv::get_fnv1a32("Hello world!"));
  |                                ^^^ use of undeclared type or module `fnv`

error[E0433]: failed to resolve: use of undeclared type or module `fnv`
  --> src\lib.rs:12:23
   |
12 |         assert_eq!(0, fnv::get_fnv1a32(""));
   |                       ^^^ use of undeclared type or module `fnv`

error: aborting due to 2 previous errors

我想不出我做错了什么。我试着改变 mod fnv; 从顶部到 pub mod fnv; 这样可以消除死代码警告,但不能修复这两个错误。我需要做什么才能得到 获取fnv1a32 函数在lib.rs文件中可见?

我认为这并不重要,但是rustc的版本是 鲁斯特C 1.41.0(5e1a79984 2020-01-27)