Crate cmp

A macro to compare structs, field by field.

This crate provides the compare_structs! macro, which is useful for writing assert!-style tests on structs. It provides more detailed output than a standard assert_eq! on two struct instances.

Basic Usage

To compare specific fields between two structs, provide the struct expressions and the identifiers of the fields to compare.

use cmp::compare_structs;
let struct_a = A { a: 1, b: "hello" };
let struct_b = B { a: 1, b: "world" };

// This will pass, as we only compare the `a` field.
compare_structs!(struct_a, struct_b, a);

serde feature

This crate has an optional serde feature that allows comparing all fields of a struct without specifying them. To use it, enable the feature in your Cargo.toml:

[dependencies]
cmp = { version = "1.0.0", features = ["serde"] }

With the serde feature enabled, you can call compare_structs! with just two arguments. The structs must derive serde::Serialize.

use cmp::compare_structs;
use serde::Serialize;

#[derive(Serialize)]
struct MyStruct {
    field1: i32,
    field2: String,
}

let a = MyStruct { field1: 1, field2: "test".to_string() };
let b = MyStruct { field1: 1, field2: "test".to_string() };

// Compares all fields
compare_structs!(a, b);

If there are missing fields in one of the expressions when using the serde feature, the macro will panic with a clear error message indicating which field is missing from which struct.

Macros

compare_structs

Macro which is mostly useful when writing assert! tests on structs.