interfaces_tests.swift

protocol Grinder {
    func grind(_ coffee: Coffee)
}
class GrinderMock: Grinder {
    private(set) var timesUsed: Int = 0
    func grind(_ coffee: Coffee) {
        timesUsed += 1
    }
}
class CoffeeMakerTest: XCTestCase {
    func test_grinder_used_once_when_coffee_made() {
        let grinder = GrinderMock()
        let sut = CoffeeMaker(grinder: grinder)
        sut.makeCoffee()
        XCTAssertEqual(grinder.timesUsed, 1)
    }
}