assert_fails

function assert_fails<T>(fn: () -> T): failure

Asserts a function fails; i.e. throws an exception.

Example

Application code

// This will throw a exception.
function bad(): integer {
    return [0][1];
}

Test code

// This test will pass.
function test_bad() {
    rell.test.assert_fails(bad(*));
    // or inline:
    rell.test.assert_fails(() -> [0][1]);
}

Parameters

• fn — the function value to invoke

Since 0.11.0

function assert_fails<T>(expected_message: text, fn: () -> T): failure

Asserts a function fails; i.e. throws an exception; with a given exception message.

Verifies that the given exception message is a substring of the exception thrown by the given function (if thrown).

Example

Application code

// This will throw a exception.
function bad(): integer {
    return [0][1];
}

Test code

// This test will pass.
function test_bad() {
    rell.test.assert_fails("out of bounds", bad(*));
    // or inline:
    rell.test.assert_fails("out of bounds", () -> [0][1]);
}

Parameters

• expected_message — the expected substring of the error message
• fn — the function value to invoke

Since 0.11.0