TestFulfill.swift

import XCTest
import Foundation

class TestFulfill: XCTestCase {
    class FulfillOnRelease {
        let ex: XCTestExpectation
        init(_ ex: XCTestExpectation) {
            self.ex = ex
        }
        deinit {
            print("Fullfiling: \(ex.description)")
            ex.fulfill()
        }
    }

    func testFulfillWithDispatchOk() {
        let queue = DispatchQueue(label: #function)
        (0..<3).forEach { index in
            let ex = expectation(description: "\(#function) \(index)")
            let fulfillOnRelease = FulfillOnRelease(ex)
            queue.async {
                print("Retaining: \(fulfillOnRelease.ex.description)")
            }
        }
        waitForExpectations(timeout: 1, handler: nil)
    }

    func testFulfillWithOperationQueueBad() {
        let queue = OperationQueue()
        (0..<3).forEach { index in
            let ex = expectation(description: "\(#function) \(index)")
            let fulfillOnRelease = FulfillOnRelease(ex)
            queue.addOperation {
                print("Retaining: \(fulfillOnRelease.ex.description)")
            }
        }
        waitForExpectations(timeout: 1, handler: nil)
    }

    func testFulfillWithOperationQueueOk() {
        let queue = OperationQueue()
        (0..<3).forEach { index in
            let ex = expectation(description: "\(#function) \(index)")
            let fulfillOnRelease = FulfillOnRelease(ex)
            let blockOperation = BlockOperation {
                print("Retaining: \(fulfillOnRelease.ex.description)")
            }
            queue.addOperation(blockOperation)
        }
        waitForExpectations(timeout: 1, handler: nil)
    }
}

Operations are under many conditions autoreleased on completion, and you cannot assume here that an object is alive or not in ObjC because they may still be in the autorelease pool. Can you try again by emptying the pool with autoreleasepool { … } and see if it's still true? We have tried and it does not reproduce in correct conditions (checking with the pool).

works with autoreleasepool, thanks