ViewInspector

When writing async tests, ViewHosting provides a closure-based API that automatically handles lifecycle management, removing the need for an explicit ViewHosting.expel() call.

Usage: Wrap your inspection logic inside try await ViewHosting.host(view) { ... }.

Handling Multiple Publishers: If your test involves multiple asynchronous events (like different publisher emissions), use a withThrowingDiscardingTaskGroup to ensure all inspection tasks subscribe to their respective publishers in time.

// Basic Async Hosting
let sut = TestView(flag: false)
try await ViewHosting.host(sut) {
    try await sut.inspection.inspect { view in
        let text = try view.button().labelView().text().string()
        XCTAssertEqual(text, "false")
        sut.publisher.send(true)
    }
}

// Async with Task Groups for multiple publishers
try await ViewHosting.host(sut) {
    try await withThrowingDiscardingTaskGroup { group in
        group.addTask {
            try await sut.inspection.inspect { view in
                // ...
            }
        }
        group.addTask {
            try await sut.inspection.inspect(onReceive: sut.publisher) { view in
                // ...
            }
        }
    }
}

To verify which button style is applied to a view, use the .buttonStyle() inspection method.

To test a ButtonStyle with different isPressed states, use the inspect(isPressed: Bool) helper function.

For PrimitiveButtonStyle, it is recommended to inspect the internal custom view directly. You can use the PrimitiveButtonStyleConfiguration(onTrigger:) initializer to provide a closure that verifies when the trigger() method is called.

// Verify button style type
XCTAssertTrue(try sut.inspect().buttonStyle() is PlainButtonStyle)

// Test ButtonStyle with specific isPressed state
func testCustomButtonStyle() throws {
    let sut = CustomButtonStyle()
    XCTAssertEqual(try sut.inspect(isPressed: false).blur().radius, 0)
    XCTAssertEqual(try sut.inspect(isPressed: true).blur().radius, 5)
}

// Test PrimitiveButtonStyle trigger mechanism
func testCustomPrimitiveButtonStyleButton() throws {
    let triggerExp = XCTestExpectation(description: "trigger()")
    triggerExp.expectedFulfillmentCount = 1
    let config = PrimitiveButtonStyleConfiguration(onTrigger: {
        triggerExp.fulfill()
    })
    let view = CustomPrimitiveButtonStyle.CustomButton(configuration: config)
    let exp = view.inspection.inspect { view in
        let label = try view.styleConfigurationLabel()
        try label.callOnTapGesture()
        // ... verify state changes
    }
    ViewHosting.host(view: view)
    wait(for: [exp, triggerExp], timeout: 0.1)
}

You can inspect a ViewModifier either as part of the view hierarchy or independently.

Hierarchy Inspection: Use .modifier(Type.self) to extract the modifier from the view hierarchy, then use .viewModifierContent() to access the content placeholder view.

Example:

let modifier = try sut.inspect().emptyView().modifier(MyViewModifier.self)
let content = try modifier.viewModifierContent()

If the modifier uses @State or @Environment, use the asynchronous inspection approaches (Approach #1 or #2) described in the main guide.

func testCustomViewModifierAppliedToHierarchy() throws {
    let sut = EmptyView().modifier(MyViewModifier())
    let modifier = try sut.inspect().emptyView().modifier(MyViewModifier.self)
    let content = try modifier.viewModifierContent()
    XCTAssertTrue(try content.hasPadding(.top))
    XCTAssertEqual(try content.padding(.top), 15)
}

If your watchOS project uses the @main attribute, follow these steps to enable ViewInspector:

1. Ensure you have a WKExtensionDelegate and reference it in your App struct using the @WKExtensionDelegateAdaptor property wrapper.
2. Add let testViewSubject = TestViewSubject([]) as an instance variable to your ExtensionDelegate.
3. Apply the .testable(extDelegate.testViewSubject) modifier to your root view (e.g., ContentView) inside the WindowGroup.

Note: The implementation uses conditional compilation (#if !(os(watchOS) && DEBUG)) to ensure that TestViewSubject and the .testable() modifier are stripped out in Release builds.

final class ExtensionDelegate: NSObject, WKExtensionDelegate {
    let testViewSubject = TestViewSubject([]) // #2
}

@main
struct MyWatchOSApp: App {
    
    @WKExtensionDelegateAdaptor(ExtensionDelegate.self) var extDelegate // #1
    
    var body: some Scene {
        WindowGroup {
            ContentView()
                .testable(extDelegate.testViewSubject) // #3
        }
    }
}