# Proxied Promise Chain

Commands and assertions in tuiv are issued in a chain.

# Commands

tuiv is based on playwright, here's what commands look like without a chain:

const element = await page.waitForSelector('.selector')
await element.click()
await element.type('some text')

For single commands, we do not need a variable, but we still would need multiple awaits:

await (await page.waitForSelector('.selector')).click()

With chains, we can get rid of multiple awaits and local variables and write our commands like this:

await page.get('.selector').click().type('some text')

# Assertions

Playwright comes with expect style assertions:

const alt = await page.getAttribute('input', 'alt')
expect(alt).toBe('Text')

with chains, we can lean even more into natural language looking assertions:

await page.get('input').should.have.attr('alt').equaling('text')

You can go over board with the natural-ish language as much as you like:

await page.get('input').should.have.an.attribute('alt').which.equals('text')

Or not at all:

await page.get('input').should.attr('alt')('text')

The biggest difference between tuivs assertions and playwrights though is retryability. tuiv will retry the whole chain, including re-fetching the attribute content and assert until the timeout is reached.

# Chain branches

tuivs chains are branchable, so you don't need to hold back with any variables at all.

const root = page.get('.my-root')
await root.find('.some-child').click()
await root.find('.some-other-child').type('some text')

Each chain will resolve on promise await.

# Benefits from using chains

• cleaner api
• less local variables and awaiting
• retry-ability

# How does it work?

Each chain starts at the page object, which is a playwright Page wrapped in a Proxy. Each call on the page in turn returns another proxy, which records all property accesses and function calls. Finally, the whole chain gets resolved at once when calling then at the end of the chain, which is what await does for us.