Unit testing WKNavigationDelegate functions

问题

I have a UIViewController that implements some WKNavigationDelegate functions, and I want to unit test the logic in these functions. Here's an example:

func webView(_ webView: WKWebView,
             decidePolicyFor navigationAction: WKNavigationAction,
             decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
    guard let url = navigationAction.request.url else {
        decisionHandler(.cancel)
        return
    }

    if url.absoluteString != "https://my-approved-url" {
        decisionHandler(.cancel)
        return
    }

    decisionHandler(.allow)
}

I'd like my unit test to make sure decisionHandler is called with the right WKNavigationActionPolicy based on the request.url of the WKNavigationAction.

I can't figure out how to test this function, however. Calling .load() on the webview does not trigger the delegate functions when I'm running my test project. I have also tried to call this function directly to test it, but it doesn't seem to be possible to instantiate a new WKNavigationAction of my own (.request is read-only).

What is the right way to unit test logic in WKNavigationDelegate functions?

回答1:

Directly calling the delegate method is the most appropriate approach in the context of a unit test. You can subclass WKNavigationAction, and pass an instance of that class as input argument to the delegate method:

class FakeNavigationAction: WKNavigationAction {
    let testRequest: URLRequest
    override var request: URLRequest {
        return testRequest
    }

    init(testRequest: URLRequest) {
        self.testRequest = testRequest
        super.init()
    }
}

Later on, in the unit test:

// setup
var receivedPolicy: WKNavigationActionPolicy?
let fakeAction = FakeNavigationAction(testRequest: ...)

// act
delegateObject.webView(webView, decidePolicyFor: fakeAction, decisionHandler: { receivedPolicy = $0 })

// assert
XCTAssertEqual(receivedPolicy, theExpectedValue)

Another approach would be to swizzle the getter for request, since WKNavigationAction is an Objective-C class, however that's more of a hacky solution.

来源：https://stackoverflow.com/questions/49277915/unit-testing-wknavigationdelegate-functions

标签

swift

webkit