RandomDate.swift

import Foundation
import XCTest

infix operator >?< : DefaultPrecedence
extension Date {
    /// Generate a random date between two dates - Dates do not need to be in order
    /// - Parameters:
    ///   - start: first date
    ///   - end: second date
    /// - Returns: Random `Date` between two dates
    static func randomBetween(start: Date, end: Date) -> Date {
        Date(timeIntervalSince1970:
                TimeInterval.random(
                    in: min(start, end).timeIntervalSince1970
                        ... max(start, end).timeIntervalSince1970)
        )
    }
    
    /// Generate a random date between two dates - Dates do not need to be in order
    /// - Parameters:
    ///   - start: first date
    ///   - end: second date
    ///   - generator: `RandomNumberGenerator`
    /// - Returns: Random `Date` between two dates
    static func randomBetween<T: RandomNumberGenerator>(start: Date, end: Date, using generator: inout T) -> Date {
        Date(timeIntervalSince1970:
                TimeInterval.random(
                    in: min(start, end).timeIntervalSince1970
                        ... max(start, end).timeIntervalSince1970,
                    using: &generator
                )
        )
    }
    
    /// Generate a random date between two dates - Dates do not need to be in order
    /// - Parameters:
    ///   - start: first date
    ///   - end: second date
    /// - Returns: Random `Date` between two dates
    static func >?< (lhs: Self, rhs: Self) -> Self {
        randomBetween(start: lhs, end: rhs)
    }
}

// MARK: Tests
class RandomDateTests: XCTestCase {
    func testRandom() {
        let date1 = Date(timeIntervalSince1970: 100_000)
        let date2 = Date(timeIntervalSince1970: 150_000)
        
        let randomDate = Date.randomBetween(start: date1, end: date2)
        XCTAssertTrue(date1...date2 ~= randomDate)
        
        let anotherRandomDate = date1 >?< date2
        XCTAssertTrue(date1...date2 ~= anotherRandomDate)
    }
}

RandomDateTests.defaultTestSuite.run()