如何在SwiftUI快照测试中覆写无障碍环境属性值？

要验证SwiftUI视图对指定无障碍环境属性的响应，你可以直接借助SwiftUI的.environment修饰符，在快照测试环节为目标视图覆写这些属性值，再结合Point-Free快照测试库生成对应状态的快照。

单个属性覆写示例 #

以测试accessibilityDifferentiateWithoutColor开启状态为例，测试代码如下：

import XCTest
import SnapshotTesting
import SwiftUI

final class MyViewTests: XCTestCase {
    func testAccessibilityDifferentiateWithoutColorEnabled() {
        let view = MyView()
            .environment(\.accessibilityDifferentiateWithoutColor, true)
        
        assertSnapshot(matching: view, as: .image)
    }
}

多属性组合测试 #

若需验证多个属性同时生效的场景，可链式调用多个.environment修饰符：

func testCombinedAccessibilitySettings() {
    let view = MyView()
        .environment(\.accessibilityReduceTransparency, true)
        .environment(\.accessibilityReduceMotion, true)
        .environment(\.accessibilityInvertColors, true)
    
    assertSnapshot(matching: view, as: .image)
}

批量覆盖所有属性状态 #

你可以遍历属性的布尔值组合，批量生成不同状态的快照，确保覆盖所有测试场景：

func testAllAccessibilityStates() {
    let accessibilityScenarios = [
        (identifier: "differentiateWithoutColor_on", modifier: { $0.environment(\.accessibilityDifferentiateWithoutColor, true) }),
        (identifier: "differentiateWithoutColor_off", modifier: { $0.environment(\.accessibilityDifferentiateWithoutColor, false) }),
        (identifier: "reduceTransparency_on", modifier: { $0.environment(\.accessibilityReduceTransparency, true) }),
        (identifier: "reduceTransparency_off", modifier: { $0.environment(\.accessibilityReduceTransparency, false) }),
        (identifier: "reduceMotion_on", modifier: { $0.environment(\.accessibilityReduceMotion, true) }),
        (identifier: "reduceMotion_off", modifier: { $0.environment(\.accessibilityReduceMotion, false) }),
        (identifier: "invertColors_on", modifier: { $0.environment(\.accessibilityInvertColors, true) }),
        (identifier: "invertColors_off", modifier: { $0.environment(\.accessibilityInvertColors, false) })
    ]
    
    for scenario in accessibilityScenarios {
        let modifiedView = scenario.modifier(MyView())
        assertSnapshot(matching: modifiedView, as: .image, named: scenario.identifier)
    }
}

注意：如果你的视图依赖其他环境值，需在测试时一并设置，保证测试环境的完整性。

内容的提问来源于stack exchange，提问作者Zev Eisenberg