Unit testing

The serde_test crate provides a convenient concise way to write unit tests for implementations of Serialize and Deserialize.

The Serialize impl for a value can be characterized by the sequence of Serializer calls that are made in the course of serializing the value, so serde_test provides a Token abstraction which corresponds roughly to Serializer method calls. It provides an assert_ser_tokens funtion to test that a value serializes into a particular sequence of method calls, an assert_de_tokens function to test that a value can be deserialized from a particular sequence of method calls, and an assert_tokens function to test both directions. It also provides functions to test expected failure conditions.

Here is an example from the linked-hash-map crate.

extern crate linked_hash_map;
use linked_hash_map::LinkedHashMap;

extern crate serde_test;
use serde_test::{Token, assert_tokens};

#[test]
fn test_ser_de_empty() {
    let map = LinkedHashMap::<char, u32>::new();

    assert_tokens(&map, &[
        Token::Map(Some(0)),
        Token::MapEnd,
    ]);
}

#[test]
fn test_ser_de() {
    let mut map = LinkedHashMap::new();
    map.insert('b', 20);
    map.insert('a', 10);
    map.insert('c', 30);

    assert_tokens(&map, &[
        Token::Map(Some(3)),
        Token::Char('b'),
        Token::I32(20),

        Token::Char('a'),
        Token::I32(10),

        Token::Char('c'),
        Token::I32(30),
        Token::MapEnd,
    ]);
}