如何在 XCTest 中测试 UIFontMetrics UIFont.TextStyle

Question

How can I test the given UIFont.TextStyle for a UIFont with a dynamic font size via UIFontMetrics in XCTest unit testing?

var myDynamicFont: UIFont {
    let font = UIFont(name: "Font-Name", size: 42)
    return UIFontMetrics(forTextStyle: .largeTitle).scaledFont(for: font)
}

XCTest Unit Test:

func testMyDynamicFont() {
    ...
    XCTAssertEqual(myDynamicFont.???, .largeTitle) // <-- How to check the given TextStyle?
}

Thanks!

Answer 1

You can use SnapshotTesting :

func test_myDynamicFont_matchesSnapshot() {
    assertSnapshot(matching: myDynamicFont, as: .dump)
}

Snapshot with.dump strategy will produce something like that:

- <UICTFont> font-family: ".SFUI-Regular"; font-weight: normal; font-style: normal; font-size: 42.00pt

Or you can use your view to produce.image snapshot and match it:

func test_label_matchesSnapshot() {
    let label = UILabel()
    label.text = "some text"
    label.sizeToFit()
    label.font = myDynamicFont
    assertSnapshot(matching: label, as: .image, record: true)
}

This will produce image snapshot:

and will match it every time you run tests.