A quick Prime Factors kata in Swift

PrimeFactors.swift

import XCTest

func primeFactors(n: Int) -> Int[] {
    
    if n == 1 {
        return [1]
    }
    
    var result: Int[] = []
    
    var number = n
    var divisor = 2
    
    func testDivisor(divisor: Int) {
        while number > divisor && number % divisor == 0 {
            result.append(divisor);
            number /= divisor
        }
    }
    
    testDivisor(2)

    for var i = 3; Double(i) <= sqrt(Double(n)); i += 2 {
        testDivisor(i)
    }
    
    if number > 1 {
        result.append(number)
    }
    
    return result
}

class SwiftPrimeFactorsTests: XCTestCase {
    
    func testOne() {
        
        XCTAssert(primeFactors(1) == [1], "The prime factor of 1 is 1")
        
    }
    
    func testTwo() {
        
        XCTAssert(primeFactors(2) == [2], "The prime factor of 2 is 2")
        
    }
    
    func testThree() {
        
        let expected: Int[] = [3]
        
        XCTAssert(primeFactors(3) == [3], "The prime factor of 3 is 3")
        
    }

    func testFour() {
        
        XCTAssert(primeFactors(4) == [2, 2], "The prime factors of 4 are [2, 2]")
        
    }
    
    func testFive() {
        
        XCTAssert(primeFactors(5) == [5], "The prime factor of 5 is 5")
        
    }
    
    func testSix() {
        
        XCTAssert(primeFactors(6) == [2, 3], "The prime factors of 6 are [2, 3]")
        
    }
    
    func testSeven() {
        
        XCTAssert(primeFactors(7) == [7], "The prime factor of 7 is [7]")
        
    }
    
    func testEight() {
        
        XCTAssert(primeFactors(8) == [2, 2, 2], "The prime factors of 2 are [2, 2, 2]")
        
    }
    
    func testNine() {
        
        XCTAssert(primeFactors(9) == [3, 3], "The prime factors of 9 are [3, 3]")
        
    }
    
    func testLargeNumber() {
        
        XCTAssert(primeFactors(1155) == [3, 5, 7, 11], "The prime factors of 1155 are [3, 5, 7, 11]")
        
    }
    
    func testAbsurdNumber() {
        
        let candidate = 2 * 2 * 3 * 3 * 5 * 5 * 7 * 11 * 13
        
        XCTAssert(primeFactors(candidate) == [2, 2, 3, 3, 5, 5, 7, 11, 13], "The prime factors of \(candidate) are [2, 2, 3, 3, 5, 5, 7, 11, 13]")
        
    }
    
}