should_match

Pass a test if the output matches a pattern.

TL;DR

use macro_rules_attr::apply;
use should_match::{should_err, test_some};

// Pass the test if the output is `Err`
#[test]
#[apply(should_err)]
fn test_should_err() -> Result<(), &'static str> {
    Err("error")
}

// Pass the test if the output is `Some`
// `test_*` macros automatically add `#[test]` for you
#[apply(test_some)]
fn test_test_some() -> Option<i32> {
    Some(42)
}

Read on for detailed, bottom-up reference.

Features

This library is lightweight and fast, based on macro_rules without any dependencies.

Setup

This crate is primarily intended for use in tests, so add it to your dev-dependencies instead of dependencies:

cargo add --dev should_match

Recommended to work with macro_rules_attr, which provides nice syntactic sugar:

cargo add --dev macro_rules_attr should_match

The should_match macro

The should_match macro wraps given function and asserts that its output matches the specified pattern. Note that:

• The function must not accept any arguments.
• The function must return something - there's no point matching ().

With macro_rules_attr

Simply apply the should_match macro, and specify your pattern (the order of #[test] and should_match does not matter):

use macro_rules_attr::apply;
use should_match::should_match;

// This test will pass
#[apply(should_match, pattern = Err("error"))]
#[test]
fn test_apply_first() -> Result<(), &'static str> {
    Err("error")
}

// This test will also pass
#[test]
#[apply(should_match, pattern = Err("error"))]
fn test_apply_second() -> Result<(), &'static str> {
    Err("error")
}

To specify a custom panic message when it fails, pass an additional message argument:

# use macro_rules_attr::apply;
# use should_match::should_match;
#
#[test]
#[apply(should_match, pattern = Err(_), message = "Expected `Err`, but got `Ok`")]
fn test_with_custom_message() -> Result<(), &'static str> {
    Err("error")
}

Direct usage

You can also use the should_match macro directly, but note that #[test] must be wrapped inside the macro:

use should_match::should_match;

// Without custom message
should_match! {
    #[test]
    fn test_match_direct() -> Result<(), &'static str> {
        Err("error")
    },
    pattern = Err("error")
}

// With custom message
should_match! {
    #[test]
    fn test_match_direct_custom_message() -> Result<(), &'static str> {
        Err("error")
    },
    pattern = Err("error"),
    message = "Expected `Err`, but got `Ok`"
}

Shortcuts

should_* shortcuts

should_match provides some shortcuts for common patterns:

An example of using should_err:

use macro_rules_attr::apply;
use should_match::should_err;

#[test]
#[apply(should_err)]
fn test_should_err() -> Result<(), &'static str> {
    Err("error")
}

Other shortcuts can be used in the same way.

test_* shortcuts

Basically should_* + #[test]. Available shortcuts:

• test_match
• test_ok
• test_err
• test_none
• test_some

An example of using test_err:

use macro_rules_attr::apply;
use should_match::test_err;

// Note that we don't need `#[test]` here - the macro will add it for us
#[apply(test_err)]
fn test_test_err() -> Result<(), &'static str> {
    Err("error")
}

Define custom shortcuts

Defining should_* shortcuts:

use macro_rules_attr::apply;

macro_rules! should_three {(
    $($target:tt)*
) => {
    ::should_match::should_match! {
        $($target)*,
        pattern = $crate::Custom::Three, // Specify the pattern
        message = "Expected `Three`, but got something else" // Specify the message (optional)
    }
}}

#[test]
#[apply(should_three)]
fn test_custom_err() -> Custom {
    Custom::Three
}

Defining test_* shortcuts:

use macro_rules_attr::apply;

macro_rules! test_three {(
    $($target:tt)*
) => {
    ::should_match::test_match! {
        $($target)*,
        pattern = $crate::Custom::Three, // Specify the pattern
        message = "Expected `Three`, but got something else" // Specify the message (optional)
    }
}}

#[apply(test_three)]
fn test_test_custom_err() -> Custom {
    Custom::Three
}