[Feature] add a expect.toFail equivalent

[A-ZC-Lau]

So we have a .toPass now, and I was wondering if we could have a .toFail equivalent.

For example, I have the function which tests an array of lessThan:

function LESS_THAN (input : [number, number][]) {
	for (const row of input) {
		test.expect(row[0]).toBeLessThan(row[1]);
	}
}

const passing = [ [1, 2], [3, 4], [5, 6] ]
test("expect to pass", () => LESS_THAN(passing));

const failing = [ [1, 2], [4, 3], [5, 6] ];
test("expect to fail", () => LESS_THAN(failing));

[dgozman]

@A-ZC-Lau Perhaps, expect(fn).not.toPass() would work for you?

[A-ZC-Lau]

@dgozman my tests still fail, the "not" doesn't seem to have any effect.

[dgozman]

@A-ZC-Lau Could you please share the exact snippet you run? The original snippet fails, but that's expected. How do you want to use toFail here? I thought you'd use toPass and not.toPass, but sounds like you are doing something else?

[A-ZC-Lau]

@dgozman

function CHECK_BLOCK_TIMING (vtt : any) {
	for (const file of vtt) {
		let previous : null | number = null;
		for (const block of file) {
			if (previous !== null) {
				test.expect.soft(previous, JSON.stringify(block)).toBeLessThanOrEqual(block[1]);
			}
			test.expect.soft(block[1], JSON.stringify(block)).toBeLessThanOrEqual(block[2]);
			previous = block[2];
		}
	}
}
test.describe("CHECK_BLOCK_TIMING", function () {
	test("failed inner timing", async function () {
		const failTiming = [
			[
				["Wales",2.1,2.5,1],
				["and",2.6,2.3,1],
				["Victoria",2.6,3.2,1],
			],
		];
		test.expect(() => {
			Helpers.CHECK_BLOCK_TIMING(failTiming);
		}).not.toPass({timeout : 5000});
	});
	test("failed in between timing", async function () {
		const failTiming = [
			[
				["Wales",2.1,2.5,1],
				["and",2.5,2.6,1],
				["Victoria",2.5,3.2,1],
			],
		];
		test.expect(() => {
			Helpers.CHECK_BLOCK_TIMING(failTiming);
		}).not.toPass({timeout : 5000});
	});
});

I still get a failed test, e.g.

Let me know if a codesandbox is needed.

[dgozman]

Thank you, I can repro.