Testing Swift

Why test?

To develop the app better. Also, it helps to understand our expectations.

Commands

CMD + U --> Starts the test in XCode

Details

import XCTest --> Imports the framework

By default, all types and their properties have an "internal" protection level. @testable attribute automatically gives your tests the same access to code.

Private code is supposed to be private, and so it should NOT be tested.

Lifecycle

class func setup() -> setup() -> testFunc1() -> teardown() -> setup() -> testFunc2() -> teardown -> class func teardown()

Example Unit Test

struct Converter {
    func converToCelsius(fahrenfeit: Double) -> Double {
        return (fahrenheit - 32) * 5 / 9
    }
}

func testFahrenheitToCelsius() {
    let sut = Converter()
    
    let input1 = 30.0
    let output1 = sut.convertToCelsius(fahrenheit: input1)
    XCTAssertEqual(output1, 0)

    let input2 = 210.0
    let output2 = sut.convertToCelsius(fahrenheit: input2)
    XCTAssertEqual(output2, 100)
}

Note: sut is special for unit tests. It's short for "system under test" and its used to refer whatever object you are testing in the code.