Very simple automated test to ensure localizations exist and are well-formed on iOS.

L10NTests.swift

import Foundation
import XCTest

/// Basic sanity check that ensures that we are able to retrieve localized strings for all languages
/// we support.
final class L10NTests: XCTestCase {

    func testLocalizations() {
        let locales = ["en", "es", "zh-Hans", "zh-Hant", "fi"]
        for locale in locales {
            verify(localeIdentifier: locale)
        }
    }

}

extension L10NTests {
    /// Verifies a localization is available by fetching one string from the Localizable.strings file.
    func verify(localeIdentifier: String) {
        guard let path = Bundle.main.path(forResource: localeIdentifier, ofType: "lproj"),
            let bundle = Bundle(path: path) else {
                XCTFail("Missing localization for \(localeIdentifier)"); return
        }

        // Pick any string from the Localizable.strings file; ideally one that's unlikely to be removed ;)
        let string = bundle.localizedString(forKey: "generic.delete", value: nil, table: nil)

        XCTAssertFalse(string.isEmpty)
        XCTAssertNotEqual(string, "generic.delete")
    }
}