Fixtures

ℹ️ How can you modify the type signatures of your production code without having to update the tests that consume them too❓

🅰️ By decoupling the tests from the production object initialization code with fixtures.

💈範例

Define a fixture extension:

// MenuItem+fixture.swift 
@testable import Albertos 
extension MenuItem {
    // ⭐️ fixture
    static func fixture( 
        category: String = "category", 
        name    : String = "name" 
    ) -> MenuItem 
    {
        // ⭐️ production object initialization code
        MenuItem(category: category, name: name) 
    }
}

and update our test code from:

func testMenuItems() {
    let menu = [ 
        // ⭐️ production object initialization code
        MenuItem(category: "pastas", name: "name"), 
        MenuItem(category: "pastas", name: "other name"), 
    ]
    // ...
}

to:

func testMenuItems() {
    let menu = [ 
        // ⭐️ using fixtures (decoupling production init code)
        MenuItem.fixture(category: "pastas", name: "name"), 
        MenuItem.fixture(category: "pastas", name: "other name"), 
    ]
    // ...
}

📗 參考

• Test-Driven Development in Swift (2021), p.69