As a follow-up to #3345:

How should we expose APIs or other affordances to help people write correct unit tests that involve Realms?

I talked with Thomas briefly about just exposing [RLMRealm resetRealmState] to public users. It turns out that this method is difficult to use correctly (i.e. in a way that won't cause tests to crash nondeterministically).

We have some shared test code that we use for our own tests. Perhaps we could expose an XCTest-agnostic helper class that abstracts out whatever we need to do to make tests run correctly, and have users use that instead? Strawman example:

class RealmUnitTestHelper {
    init(setupBlock: RealmTestBlock = nil, teardownBlock: RealmTestBlock = nil)

    // In-memory Realm is named automatically
    func runTest(testBlock: RealmTestBlock)

    func runTestWithRealmNamed(name: String, testBlock: RealmTestBlock)
}

// Usage:
class MyTest : XCTestCase {
    let helper = RealmUnitTestHelper(setupBlock: { ... }, teardownBlock: { ... })

    func testFoo() {
        helper.runTest() { ... }
    }

    func testBar() {
        helper.runTest() { ... }
    }
}

Any other ideas are welcome.

@bdash @tgoyne @jpsim @mrackwitz @kishikawakatsumi @stel