Unit testing with Realm in iOS

Question

I followed the guidance on the Realm website, but my test still produces different results, depending on what order they are performed.

Either they succeed when they are run individually, or they fail because the data is already installed. For instance:

XCTAssert(observer.events[0].value.element == "", "Initail hub name is expected to be equal to be an empty string but was \(String(describing: observer.events[0].value.element))")
XCTAssert(observer.events[1].value.element == testHubName, "Initail hub name is expected to be equal to be the name we set but was \(String(describing: observer.events[1].value.element))")

This example is event[0]already set to testHubName. Or he gets. @throw RLMException(@"Object has been deleted or invalidated.");
Therefore, I assume that some kind of race is going on, but this is in my method setup:

func setupRealm() {
    testRealm = try! Realm(configuration: Realm.Configuration(inMemoryIdentifier: "DORSessionViewModelTestsRealm"))
    try! self.testRealm.write {
        self.testRealm.deleteAll()
    }
}

So, as I understand it, I have to have a new kingdom for each test, so where is the race going?

Edit: Adding most of the class

class DORSessionViewModelTests: XCTestCase {

var disposeBag: DisposeBag = DisposeBag()
var scheduler = TestScheduler(initialClock: 0)
var testRealm: Realm!


override func setUp() {

    super.setUp()
    setupRealm()
    setupRx()
}


override func tearDown() {
    super.tearDown()
}

func testHubNameLabelTextUpdate() {
    let expectation = self.expectation(description: "expect hub name text to update")
    let testHubName = "testHubName"
    let viewModel = getSessionViewModel()

    let observer = scheduler.createObserver(String.self)
    scheduler.start()
    let hubNameDriver = viewModel.hubNameLabelText()
    hubNameDriver.asObservable().subscribe(observer).disposed(by: disposeBag)
    hubNameDriver.asObservable().skip(1).subscribeNext { _ in expectation.fulfill()}.disposed(by: disposeBag)

    try! self.testRealm.write {
        viewModel.dependencies..hub.name = testHubName
    }


    waitForExpectations(timeout: 5, handler: { error in
        XCTAssert(observer.events[0].value.element == "", "Initail hub name is expected to be equal to be an empty string but was \(String(describing: observer.events[0].value.element))")
        XCTAssert(observer.events[1].value.element == testHubName, "Initail hub name is expected to be equal to be the name we set but was \(String(describing: observer.events[1].value.element))")
    })
}

func setupRx() {
    disposeBag = DisposeBag()
    scheduler = TestScheduler(initialClock: 0)
}