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chore: Add some basic testing.
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‎Tests/DispatchAsyncTests/DispatchGroupTests.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2025 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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import Testing
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@testable import DispatchAsync
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@Test
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func dispatchGroupOrderCleanliness() async throws {
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// Repeating this 100 times to help rule out
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// edge cases that only show up some of the time
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for index in 0 ..< 100 {
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Task {
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actor Result {
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private(set) var value = ""
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func append(value: String) {
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self.value.append(value)
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}
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}
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let result = Result()
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let group = DispatchGroup()
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await result.append(value: "|🔵\(index)")
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group.enter()
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Task {
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await result.append(value: "🟣/")
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group.leave()
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}
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group.enter()
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Task {
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await result.append(value: "🟣^")
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group.leave()
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}
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group.enter()
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Task {
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await result.append(value: "🟣\\")
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group.leave()
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}
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await withCheckedContinuation { continuation in
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group.notify(queue: .main) {
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Task {
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await result.append(value: "🟢\(index)=")
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continuation.resume()
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}
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}
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}
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let finalValue = await result.value
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/// NOTE: If you need to visually debug issues, you can uncomment
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/// the following to watch a visual representation of the group ordering.
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///
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/// In general, you'll see something like the following printed over and over
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/// to the console:
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///
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/// ```
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/// |🔵42🟣/🟣^🟣\🟢42=
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/// ```
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///
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/// What you should observe:
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///
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/// - The index number be the same at the beginning and end of each line, and it
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/// should always increment by one.
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/// - The 🔵 should always be first, and the 🟢 should always be last for each line.
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/// - There should always be 3 🟣's in between the 🔵 and 🟢.
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/// - The ordering of the 🟣 can be random, and that is fine.
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///
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/// For example, for of the following are valid outputs:
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///
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/// ```
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/// // GOOD
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/// |🔵42🟣/🟣^🟣\🟢42=
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/// ```
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///
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/// ```
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/// // GOOD
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/// |🔵42🟣/🟣\🟣^🟢42=
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/// ```
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///
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/// But the following would not be valid:
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///
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/// ```
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/// // BAD!
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/// |🔵43🟣/🟣^🟣\🟢43=
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/// |🔵42🟣/🟣^🟣\🟢42=
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/// |🔵44🟣/🟣^🟣\🟢44=
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/// ```
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///
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/// ```
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/// // BAD!
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/// |🔵42🟣/🟣^🟢42🟣\=
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/// ```
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///
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// Uncomment to use troubleshooting method above:
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// print(finalValue)
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#expect(finalValue.prefix(1) == "|")
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#expect(finalValue.count { $0 == "🟣"} == 3)
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#expect(finalValue.count { $0 == "🟢"} == 1)
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#expect(finalValue.lastIndex(of: "🟣")! < finalValue.firstIndex(of: "🟢")!)
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#expect(finalValue.suffix(1) == "=")
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}
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}
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}
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‎Tests/DispatchAsyncTests/DispatchQueueTests.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2025 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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import Testing
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@testable import DispatchAsync
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#if !os(WASI)
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import class Foundation.Thread
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#endif
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@Test
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func testBasicDispatchQueueMain() async throws {
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let asyncValue = await withCheckedContinuation { continuation in
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DispatchQueue.main.async {
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// Main queue should be on main thread.
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#if !os(WASI)
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#expect(Thread.isMainThread)
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#endif
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continuation.resume(returning: true)
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}
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}
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#expect(asyncValue == true)
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}
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@Test
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func testBasicDispatchQueueGlobal() async throws {
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let asyncValue = await withCheckedContinuation { continuation in
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DispatchQueue.global().async {
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// Global queue should NOT be on main thread.
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#if !os(WASI)
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#expect(!Thread.isMainThread)
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#endif
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continuation.resume(returning: true)
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}
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}
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#expect(asyncValue == true)
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}

‎Tests/DispatchAsyncTests/DispatchSemaphoreTests.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2025 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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import Testing
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@testable import DispatchAsync
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nonisolated(unsafe) private var sharedPoolCompletionCount = 0
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@Test func basicDispatchSemaphoreTest() async throws {
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let totalConcurrentPools = 10
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let semaphore = DispatchSemaphore(value: 1)
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await withTaskGroup(of: Void.self) { group in
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for _ in 0 ..< totalConcurrentPools {
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group.addTask {
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// Wait for any other pools currently holding the semaphore
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await semaphore.wait()
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// Only one task should mutate counter at a time
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//
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// If there are issues with the semaphore, then
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// we would expect to grab incorrect values here occasionally,
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// which would result in an incorrect final completion count.
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//
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let existingPoolCompletionCount = sharedPoolCompletionCount
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// Add artificial delay to amplify race conditions
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// Pools started shortly after this "semaphore-locked"
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// pool starts will run before this line, unless
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// this pool contains a valid lock.
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try? await Task.sleep(nanoseconds: 100)
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sharedPoolCompletionCount = existingPoolCompletionCount + 1
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// When we exit this flow, release our hold on the semaphore
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await semaphore.signal()
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}
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}
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}
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// After all tasks are done, counter should be 10
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#expect(sharedPoolCompletionCount == totalConcurrentPools)
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}

‎Tests/DispatchAsyncTests/DispatchTimeTests.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2025 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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import Testing
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@testable import DispatchAsync
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@Test
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func testDispatchTimeContinousClockBasics() async throws {
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let a = DispatchTime.now().uptimeNanoseconds
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let b = DispatchTime.now().uptimeNanoseconds
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#expect(a <= b)
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}

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