Here is the complete list of the implemented assertions. Note that the assertions marked as consuming consume the left part of the assertion, so there cannot be a chain of multiple assertions.

Those assertions print a more complete error message in the test functions marked as #[fact] or #[attribute]. They can be used in a standard #[test] function as well, but in this case, the location and the stringified version of the left side are not displayed in the failure message.

Various feature

Negation

(2 + 2).should().not().be_equal_to(5);

Chaining

"42".parse::<i32>().should().not().be_an_error()
    .and_should().contain(42);

Explanation

the_answer().should().be_equal_to(42).because("42 is the answer to the question");

Equality

(1 + 1).should().be_equal_to(2);

With precision (for floats only):

(0.999 * 2.).should().be_equal_to(2.01).with_precision(0.1);

Iterators (consuming assertions)

Containing something

Some(2).should().contain(2);

vec![1, 2, 3].should().contain(1);

Checking if empty

let empty_vec = Vec::<i32>::new();
empty_vec.should().be_empty();

Results

Checking if it is an error

"?".parse::<i32>().should().be_an_error();

Generic

When there is no specific needed assertion:

foo().should().have_the_property(|&n| n % 2 == 0)
    .because("the number must be even");