Galvanic-assert: Matcher-based assertions for easier testing
This crate provides a new assertion macro assert_that!
based on matching predicates (matchers) to
- make writing asserts easier
- make reading asserts comprehendable
- easily extend the assertion framework
- provide a large list common matchers
- integrate with galvanic-test and galvanic-mock (both still in development ... stay tuned!)
- be used with your favourite test framework
The crate will be part of galvanic---a complete test framework for Rust.
galvanic-assert currently requires nightly until impl trait returns have been stabilized.
The 2-minute tutorial
Each assertion has the form assert_that!(SOME_VALUE, MATCHES_SOMETHING);
.
To check if some value satisfies some matching predicate, e.g., less_than
, contains_in_order
, is_variant!
, ...; we can write something like the following to when operating on a single value:
extern crate galvanic_assert;
use *;
or assert properties of collections ...
use *;
or of variants ...
It is also possible to combine multiple matchers to create more expressive ones ...
If this is not enough you can write your own matchers, either as a closure ...
or if it is easy enough, as an expression ...
If it is more complex implement the Matcher
trait for some struct representing the state of the matcher.
Asserting positive things is good, but sometimes we expect that something goes horribly wrong ...
... except when it doesn't.
Not much more to say---have a look at the documentation and the growing list of matchers.
And remember ... only tested code is happy code!
Contributions
Contributions are very welcome! (Please read and agree with the license.)
The list of included matchers is far from complete.
If you encounter a useful matcher please open an issue.
Check before if there's already a boolean predicate on the type itself, e.g., like Option::is_none()
.
Those are already supported by the assertion macros and should only be included if the error message of the Matcher
is substantially better than the default one.
If something is missing or broken, please open an issue and send (if you want to) a pull request.
For pull requests be sure to include test cases to avoid regressions.
Tests for Matchers
should be added as integration tests as they test the integration with the assertion macros.
Have a look at the existing ones!