Assertables: assert macros for better testing

Assertables is a Rust crate of assert macros to improve your compile-time tests and run-time reliability.

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Introduction

The Assertables Rust crate provides many assert macros that can help you develop, test, and debug.

This documentation is also available as llms.txt.

• Test values with assert_lt, assert_gt, assert_in, …
• Test groups with assert_all, assert_any, assert_iter, …
• Test wrappers with assert_ok, assert_some, assert_ready, …
• Test matching with assert_matches, assert_is_match, …
• Test approximations with assert_approx, assert_abs_diff, …
• Test programs with assert_command, assert_status, …
• Many more below.

To use this crate, add it to your file Cargo.toml:

assertables = "10.0.0"

To enable all the assert macros everywhere in your code, add it to your src/lib.rs:

#[cfg(test)]
#[macro_use] extern crate assertables;

Benefits:

• You can write better tests to improve reliability and maintainability.
• You can handle more corner cases without needing to write custom code.
• You can troubleshoot faster because error messages show more detail.

Learning: FAQ, docs, examples, changes, upgrades, developing.

Comparisons: more_asserts, cool_asserts, assert2, claims, etc.

Examples

Examples with numbers:

let i = 1;
assert_lt!(i, 2);
assert_in_range!(&i, 0..2);

Examples with strings:

let s = "hello";
assert_starts_with!(s, "h");
assert_is_match!(Regex::new(r"e.*o").unwrap(), s);

Examples with arrays:

let a = [1, 2, 3];
assert_contains!(a, &2);
assert_all!(a.iter(), |i: i32| i < 4);

Highlights

Values:

• assert_eq!(a, b)
• assert_ne!(a, b)
• assert_ge!(a, b)
• assert_gt!(a, b)
• assert_le!(a, b)
• assert_lt!(a, b)

Floats:

• assert_f32_eq!(a, b)
• assert_f64_eq!(a, b)

Approximations:

• assert_approx_eq!(a, b)
• assert_approx_eq_with_absolute_error!(a, b, err)
• assert_approx_eq_with_relative_error!(a, b, err)

Nearness:

• assert_in_delta!(a, b, delta)
• assert_in_epsilon!(a, b, epsilon)
• assert_in_range!(a, range)
• assert_diff_eq_x!(a, b, x)
• assert_abs_diff_eq_x!(a, b, x)

Groups:

• assert_all!(group, predicate)
• assert_any!(group, predicate)
• assert_is_empty!(group)
• assert_len_eq!(a, b)
• assert_count_eq!(a, b)

Matching:

• assert_starts_with!(sequence, x)
• assert_ends_with!(sequence, x)
• assert_contains!(container, x)
• assert_is_match!(matcher, x)
• assert_matches!(expr, pattern)
• assert_email_address!(string)

Results:

• assert_ok!(result)
• assert_ok_eq_x!(result, x)
• assert_ok_ne_x!(result, x)
• assert_err!(result)

Options:

• assert_some!(option)
• assert_some_eq_x!(option, x)
• assert_some_ne_x!(option, x)
• assert_none!(option)

Polls:

• assert_ready!(poll)
• assert_ready_eq_x!(poll, x)
• assert_ready_ne_x!(poll, x)
• assert_pending!(poll)

Readers:

• assert_fs_read_to_string_eq_x!(path, x
• assert_io_read_to_string_eq_x!(reader, x)

Iterators:

• assert_iter_eq!(a, b)
• assert_iter_ne!(a, b)
• assert_iter_ge!(a, b)
• assert_iter_gt!(a, b)
• assert_iter_le!(a, b)
• assert_iter_lt!(a, b)

Sets:

• assert_set_eq!(a, b)
• assert_set_ne!(a, b)
• assert_set_subset!(a, b)
• assert_set_superset!(a, b)

Bags:

• assert_bag_eq!(a, b)
• assert_bag_ne!(a, b)
• assert_bag_subbag!(a, b)
• assert_bag_superbag!(a, b)

Commands:

• assert_command_stdout_eq_x!(command, x)
• assert_program_args_stdout_eq_x!(program, args, x)

Status:

• assert_status_success!(a)
• assert_status_code_value_eq_x!(a, x)
• assert_status_code_value_ne_x!(a, x)
• assert_status_failure!(a)

Infix values:

• assert_infix!(a == b)
• assert_infix!(a != b)
• assert_infix!(a < b)
• assert_infix!(a <= b)
• assert_infix!(a > b)
• assert_infix!(a >= b)

Infix logic:

• assert_infix!(a & b)
• assert_infix!(a | b)
• assert_infix!(a ^ b)
• assert_infix!(a && b)
• assert_infix!(a || b)

For a complete list of modules and macros, see the docs.

Forms

All the macros have forms for an optional message:

• assert_gt!(a, b) // default message
• assert_gt!(a, b, "your text") // custom message

All the macros have forms for different outcomes:

• assert_gt!(1, 2) // panic
• assert_gt_as_result!(1, 2) return Result
• debug_assert_gt!(a, b) // panic in debug mode

Many of the macros have a form "compare left item to right item" that compares items of the same kind, and a form "compare left item to right expression" that compares one item to any arbitrary expression:

• assert_len_eq!(a, b) // a.len() = b.len()
• assert_len_eq_x!(a, x) // a.len() = x

Many of the macros has a "success return", which means the macro returns data that you can optionally use for more testing.

• let inner = assert_ok!(result)
• let string = assert_fs_read_to_string_ne!("alfa.txt", "")
• let stdout = assert_command_stdout_gt!("ls", vec![b' '])

Tracking

• Package: assertables-rust-crate
• Version: 10.0.0
• Created: 2021-03-30T15:47:49Z
• Updated: 2026-05-23T16:03:31Z
• License: MIT or BSD or Apache-2.0 or GPL-2.0 or GPL-3.0 or contact us for more
• Contact: Joel Parker Henderson joel@joelparkerhenderson.com