How to use inline documentation for tests in rust - testing

Question

I am trying to get rust to test an example from my inline documentation. I wrote the following code:
#[derive(Clone)]
#[derive(PartialEq)]
#[derive(Debug)]
enum Color {
Black = 1,
Empty = 0,
White = -1
}
/// Chages Color to the next player
///
/// Returns: White if player is Black, Black if player is White and Empty if
/// player is Empty.
///
/// Examlple
/// ```
/// assert_eq!(flip(&Color::White),Color::Black);
///```
// Invariant Color must represent Black as 1, Empty as 0 and White as -1!
fn flip(player: &Color)->Color{
let intrepresentation :i8 = (player.clone() as i8) * (-1);
unsafe{
std::mem::transmute(intrepresentation)
}
}
fn main() {
assert_eq!(flip(&Color::White),Color::Black);
}
Then I run
rustdoc --test src/main.rs
Which gave me:
running 1 test
test src/main.rs - flip (line 16) ... FAILED
failures:
---- src/main.rs - flip (line 16) stdout ----
error[E0433]: failed to resolve: use of undeclared type or module `Color`
--> src/main.rs:17:18
|
3 | assert_eq!(flip(&Color::White),Color::Black);
| ^^^^^ use of undeclared type or module `Color`
error[E0433]: failed to resolve: use of undeclared type or module `Color`
--> src/main.rs:17:32
|
3 | assert_eq!(flip(&Color::White),Color::Black);
| ^^^^^ use of undeclared type or module `Color`
error[E0425]: cannot find function `flip` in this scope
--> src/main.rs:17:12
|
3 | assert_eq!(flip(&Color::White),Color::Black);
| ^^^^ not found in this scope
error: aborting due to 3 previous errors
Some errors have detailed explanations: E0425, E0433.
For more information about an error, try `rustc --explain E0425`.
Couldn't compile the test.
failures:
src/main.rs - flip (line 16)
test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
How can I get rustc to find flip and Color. The test runs fine in the main function. I have also tried the command:
cargo test
but that did not run any tests.
I have tried add the following line to the example:
/// use crate::{flip, Color};
making:
// Chages Color to the next player
///
/// Returns: White if player is Black, Black if player is White and Empty if
/// player is Empty.
///
/// Examlple
/// ```
/// use crate::{flip, Color};
/// assert_eq!(flip(&Color::White),Color::Black);
///```
but that gives an error
martin#martin-laptop:~/test_code$ rustdoc --test src/main.rs
running 1 test
test src/main.rs - main (line 23) ... FAILED
failures:
---- src/main.rs - main (line 23) stdout ----
error[E0432]: unresolved import `crate::Color`
--> src/main.rs:24:14
|
3 | use crate::{ Color};
| ^^^^^ no `Color` in the root
error[E0425]: cannot find function `flip` in this scope
--> src/main.rs:25:12
|
4 | assert_eq!(flip(&Color::White),Color::Black);
| ^^^^ not found in this scope
error: aborting due to 2 previous errors
Some errors have detailed explanations: E0425, E0432.
For more information about an error, try `rustc --explain E0425`.
Couldn't compile the test.
failures:
src/main.rs - main (line 23)
test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
I have also tried to Color and flip as public:
#[derive(Clone)]
#[derive(PartialEq)]
#[derive(Debug)]
pub enum Color {
Black = 1,
Empty = 0,
White = -1
}
/// Chages Color to the next player
///
/// Returns: White if player is Black, Black if player is White and Empty if
/// player is Empty.
///
/// Examlple
/// ```
/// use crate::{flip, Color};
/// use std::env;
/// assert_eq!(flip(&Color::White),Color::Black);
///```
// Invariant Color must represent Black as 1, Empty as 0 and White as -1!
pub fn flip(player: &Color)->Color{
let intrepresentation :i8 = (player.clone() as i8) * (-1);
unsafe{
std::mem::transmute(intrepresentation)
}
}
fn main() {
assert_eq!(flip(&Color::White),Color::Black);
}
but that gave the same error.

Answer 1

Doc tests (tests inside /// ```) are compiled separately as tiny programs of their own. Therefore:
They can only access public items: pub mod, pub fn, pub struct, ...
They can only access library crates that export items to be used by other crates — if your program is in main.rs then it's a binary crate.
You have to fully qualify or use the names, like use my_library::Color;.
If you want to test things that don't fit this, then you should use #[test] tests instead:
#[test]
fn flip_test() {
assert_eq!(flip(&Color::White), Color::Black);
}
Any function located anywhere in your program with the attribute #[test] will be run as a test. So, they can access private items since they're in the same module (or a submodule; it's common to put them inside a module named tests in the same file, with mod tests { ... }).
You can find more information about how to write test functions and organize your tests at The Rust Programming Language: How to Write Tests.
I have also tried to Color and flip as public:
/// use crate::{flip, Color};
This doesn't work because crate refers to the current crate, which for a doc test is the test program, not your main crate.