Assertions

Web-first assertions in the library, after Playwright's: an assertion checks the page again and again until it holds or the timeout passes. A journey's expect line is the same engine.

await page.Css("#count").ExpectAsync(Matcher.Text("2 results"));
await page.Role("button", "Save").ExpectAsync(Matcher.Enabled, new ExpectOptions { Timeout = TimeSpan.FromSeconds(10) });
await page.Css(".spinner").ExpectAsync(Matcher.Visible, new ExpectOptions { Negate = true });
await page.ExpectAsync(Matcher.Url("**/checkout"));

ExpectAsync throws an ExpectationException (a TimeoutException) carrying the result. CheckAsync takes the same arguments and returns the ExpectationResult without throwing, which is what a test framework adapter reports:

ExpectationResult result = await page.Css("#count").CheckAsync(Matcher.Text("3"), new ExpectOptions { Timeout = TimeSpan.FromSeconds(1) });
result.Passed;
result.Message;   // Timed out after 1s waiting for css #count to have text "3": received "2 results".
result.Received;  // "2 results"

false

Matchers

A Matcher is data: what to check, and for text how (TextMatch.Exact, Contains or Regex). The same value is built by a journey line, by code and by an adapter.

Matcher	Holds when
`Visible`, `Hidden`	the first match is visible; `Hidden` also holds when nothing matches
`Enabled`, `Disabled`, `Checked`, `Unchecked`	the state
`Focused`, `Editable`, `Attached`, `Empty`	focus, input, in the document, no value or text
`Text(text)`, `Value(text)`	the whole text (whitespace collapsed) or value; `Contains`, `Regex`
`Attribute(name, [text])`	the attribute is present, or has the value
`Class(classes)`	the whole `class` attribute; `Contains`: every class listed
`Count(n)`	exactly `n` matches
`Title(text)`, `Url(glob)`	on a `Page`: `page.ExpectAsync(...)`

Only Visible, Hidden, Attached and Count can be asserted about nothing; every other matcher needs an element, even negated, as in Playwright: Enabled with Negate on a missing element keeps failing (received no element matches).

ExpectOptions holds the Timeout (the page's ActionTimeout, 5 s, by default), Negate, IgnoreCase, UseInnerText for Text, and the PollInterval. A negated matcher keeps checking until it stops holding.

With a test framework

The core package depends on no test framework. Because CheckAsync returns a result, an adapter only has to report it: build a Matcher, call CheckAsync, and fail the framework's assertion with result.Message. The Nullean.Cdp tests include a small AwesomeAssertions adapter (await page.Css("#count").Should().HaveTextAsync("2 results")) as proof that because reasons and AssertionScope behave. Pass the message to the framework as an argument, never as its format string: a selector or page text can hold {braces}.