Comparing different reduce algorithms

ReduceTests.swift

//  ReduceTests.swift
//  Created by Gordeev Aleksey on 27.05.2020.

import XCTest
@testable import ReduceTesting

extension Sequence {
    func reduce<Result>(
        _ initialResult: Result,
        _ nextPartialResult: (Result, Self.Iterator.Element) throws -> Result,
        until conditionPassForResult: (Result) -> Bool
    ) rethrows -> Result {
        
        return try reduce(initialResult, {
            if conditionPassForResult($0) {
                return $0
            }
            else {
                return try nextPartialResult($0, $1)
            }
        })
    }
    
    func improvedReduce<Result>(
        _ initialResult: Result,
        _ nextPartialResult: (Result, Self.Iterator.Element) throws -> Result,
        until conditionPassForResult: (Result) -> Bool
    ) rethrows -> Result {
        var result = initialResult
        for item in self {
            result = try nextPartialResult(result, item)
            guard !conditionPassForResult(result) else {
                return result
            }
        }
        return result
    }
    
}

class ReduceTestingTests: XCTestCase {
    
    let elements = (0..<10000).map({ $0 })

    func testReduceFuncsGotEqualResults() {
        let result1 = elements.reduce(0, +, until: { $0 > 500 })
        let result2 = elements.improvedReduce(0, +, until: { $0 > 500 })
        XCTAssertEqual(result1, result2)
    }
    
    func testOriginalReduce() throws {
      // Shows 0.004s (0.00367 actually)
        measure {
            _ = elements.reduce(0, +, until: { $0 > 500 })
        }
    }
    
    func testImprovedReduce() {
      // Shows 0.000s (0.0000423 actually)
        measure {
            _ = elements.improvedReduce(0, +, until: { $0 > 500 })
        }
    }
}