Assertion Functions

Functions for testing and validation. Assertion failures produce runtime errors with descriptive messages.

assert(condition, message?) -> null

Asserts that condition is truthy. Throws a runtime error if false.

assert(1 + 1 == 2)
assert(len("hello") > 0, "string should not be empty")

assert_eq(actual, expected, message?) -> null

Asserts that actual equals expected. Shows both values on failure.

assert_eq(1 + 1, 2)
assert_eq(sort([3, 1, 2]), [1, 2, 3])
assert_eq(user.name, "Alice", "user name mismatch")

assert_ne(actual, expected, message?) -> null

Asserts that actual does not equal expected.

assert_ne(1, 2)
assert_ne(user.role, "admin", "user should not be admin")

assert_throws(fn, message?) -> null

Asserts that calling fn produces a runtime error. Useful for testing error handling.

assert_throws(fn() { int("not a number") })
assert_throws(fn() { bruh "expected crash" })

satisfies(value, interface) -> bool

Checks whether value structurally satisfies an interface (Go-style structural typing). Returns true if the value has all methods specified by the interface, either through the environment or through give/impl blocks.

power Printable {
    fn to_string() -> string
}

thing User {
    name: string
}

give User {
    fn to_string() {
        return self.name
    }
}

let u = User { name: "Alice" }
assert(satisfies(u, Printable))

See the Type System chapter for more details on interface satisfaction.