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0238-reliably-testing-async-pt1/README.md

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+## [Point-Free](https://www.pointfree.co)
+
+> #### This directory contains code from Point-Free Episode: [Reliable Async Tests: The Problem](https://www.pointfree.co/episodes/ep238-reliable-async-tests)
+>
+> While Swift provides wonderful tools for writing async code, there are gaps in its tools for testing it. Let’s explore the tools it _does_ provide to show where they succeed, and where they fall short.

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsync.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsync.xcodeproj/xcshareddata/xcschemes/ReliablyTestingAsync.xcscheme

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+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "1500"
+   version = "1.7">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "CAC2DD7C2A30B827007675BD"
+               BuildableName = "ReliablyTestingAsync.app"
+               BlueprintName = "ReliablyTestingAsync"
+               ReferencedContainer = "container:ReliablyTestingAsync.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES">
+      <TestPlans>
+         <TestPlanReference
+            reference = "container:ReliablyTestingAsyncTests/ReliablyTestingAsync.xctestplan"
+            default = "YES">
+         </TestPlanReference>
+      </TestPlans>
+      <Testables>
+         <TestableReference
+            skipped = "NO"
+            parallelizable = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "CAC2DD8C2A30B829007675BD"
+               BuildableName = "ReliablyTestingAsyncTests.xctest"
+               BlueprintName = "ReliablyTestingAsyncTests"
+               ReferencedContainer = "container:ReliablyTestingAsync.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+         <TestableReference
+            skipped = "NO"
+            parallelizable = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "CAC2DD962A30B829007675BD"
+               BuildableName = "ReliablyTestingAsyncUITests.xctest"
+               BlueprintName = "ReliablyTestingAsyncUITests"
+               ReferencedContainer = "container:ReliablyTestingAsync.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+      </Testables>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "CAC2DD7C2A30B827007675BD"
+            BuildableName = "ReliablyTestingAsync.app"
+            BlueprintName = "ReliablyTestingAsync"
+            ReferencedContainer = "container:ReliablyTestingAsync.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "CAC2DD7C2A30B827007675BD"
+            BuildableName = "ReliablyTestingAsync.app"
+            BlueprintName = "ReliablyTestingAsync"
+            ReferencedContainer = "container:ReliablyTestingAsync.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsync/App.swift

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+import SwiftUI
+
+@main
+struct ReliablyTestingAsyncApp: App {
+  var body: some Scene {
+    WindowGroup {
+      ContentView(model: NumberFactModel())
+    }
+  }
+}

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsync/Assets.xcassets/AccentColor.colorset/Contents.json

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+{
+  "colors" : [
+    {
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsync/Assets.xcassets/AppIcon.appiconset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "platform" : "ios",
+      "size" : "1024x1024"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsync/Assets.xcassets/Contents.json

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+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsync/ContentView.swift

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+import Dependencies
+import SwiftUI
+
+struct NumberFactClient {
+  var fact: @Sendable (Int) async throws -> String
+}
+
+extension NumberFactClient: DependencyKey {
+  static let liveValue = Self { number in
+    try await Task.sleep(for: .seconds(1))
+    return try await String(
+      decoding: URLSession.shared.data(from: URL(string: "http://numbersapi.com/\(number)")!).0,
+      as: UTF8.self
+    )
+  }
+}
+
+extension DependencyValues {
+  var numberFact: NumberFactClient {
+    get { self[NumberFactClient.self] }
+    set { self[NumberFactClient.self] = newValue }
+  }
+}
+
+@MainActor
+class NumberFactModel: ObservableObject {
+  @Dependency(\.numberFact) var numberFact
+
+  @Published var count = 0
+  @Published var fact: String?
+  @Published var isLoading = false
+
+  func incrementButtonTapped() {
+    self.fact = nil
+    self.count += 1
+  }
+  func decrementButtonTapped() {
+    self.fact = nil
+    self.count -= 1
+  }
+  func getFactButtonTapped() async {
+    self.isLoading = true
+    defer { self.isLoading = false }
+
+    self.fact = nil
+    do {
+      self.fact = try await self.numberFact.fact(self.count)
+    } catch {
+      // TODO: handle error
+    }
+  }
+}
+
+struct ContentView: View {
+  @ObservedObject var model: NumberFactModel
+
+  var body: some View {
+    Form {
+      Section {
+        HStack {
+          Button("-") { self.model.decrementButtonTapped() }
+          Text("\(self.model.count)")
+          Button("+") { self.model.incrementButtonTapped() }
+        }
+      }
+      .buttonStyle(.plain)
+
+      HStack {
+        Button("Get fact") {
+          Task { await self.model.getFactButtonTapped() }
+        }
+        if self.model.isLoading {
+          Spacer()
+          ProgressView()
+        }
+      }
+
+      if let fact = self.model.fact {
+        Text(fact)
+      }
+    }
+  }
+}
+
+struct ContentPreviews: PreviewProvider {
+  static var previews: some View {
+    ContentView(model: NumberFactModel())
+  }
+}

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsync/Info.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>NSAppTransportSecurity</key>
+	<dict>
+		<key>NSAllowsArbitraryLoads</key>
+		<true/>
+	</dict>
+</dict>
+</plist>

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsync/Preview Content/Preview Assets.xcassets/Contents.json

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+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsyncTests/LockIsolated.swift

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+import Foundation
+
+public final class LockIsolated<Value>: @unchecked Sendable {
+  private var _value: Value
+  private let lock = NSRecursiveLock()
+  public init(_ value: @autoclosure @Sendable () throws -> Value) rethrows {
+    self._value = try value()
+  }
+  public func withValue<T: Sendable>(
+    _ operation: (inout Value) throws -> T
+  ) rethrows -> T {
+    try self.lock.withLock {
+      var value = self._value
+      defer { self._value = value }
+      return try operation(&value)
+    }
+  }
+}
+
+extension LockIsolated where Value: Sendable {
+  public var value: Value {
+    self.lock.withLock {
+      self._value
+    }
+  }
+}

0238-reliably-testing-async-pt1/ReliablyTestingAsync/ReliablyTestingAsyncTests/NumberFactModelTests.swift

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+import Dependencies
+import XCTest
+@testable import ReliablyTestingAsync
+
+@MainActor
+final class NumberFactModelTests: XCTestCase {
+  func testIncrementDecrement() {
+    let model = NumberFactModel()
+    model.incrementButtonTapped()
+    XCTAssertEqual(model.count, 1)
+    model.decrementButtonTapped()
+    XCTAssertEqual(model.count, 0)
+  }
+
+  func testGetFact() async {
+    let model = withDependencies {
+      $0.numberFact.fact = { "\($0) is a good number." }
+    } operation: {
+      NumberFactModel()
+    }
+    await model.getFactButtonTapped()
+    XCTAssertEqual(model.fact, "0 is a good number.")
+
+    model.incrementButtonTapped()
+    XCTAssertEqual(model.fact, nil)
+
+    await model.getFactButtonTapped()
+    XCTAssertEqual(model.fact, "1 is a good number.")
+  }
+
+  func testFactClearsOut() async {
+    let fact = AsyncStream.makeStream(of: String.self)
+
+    let model = withDependencies {
+      $0.numberFact.fact = { _ in
+        await fact.stream.first(where: { _ in true })!
+      }
+    } operation: {
+      NumberFactModel()
+    }
+    model.fact = "An old fact about 0."
+
+    let task = Task { await model.getFactButtonTapped() }
+    await Task.yield()
+    XCTAssertEqual(model.fact, nil)
+    fact.continuation.yield("0 is a good number.")
+    await task.value
+    XCTAssertEqual(model.fact, "0 is a good number.")
+  }
+
+  func testFactIsLoading() async {
+    let fact = AsyncStream.makeStream(of: String.self)
+
+    let model = withDependencies {
+      $0.numberFact.fact = { _ in
+        await fact.stream.first(where: { _ in true })!
+      }
+    } operation: {
+      NumberFactModel()
+    }
+    model.fact = "An old fact about 0."
+
+    let task = Task { await model.getFactButtonTapped() }
+    await Task.yield()
+    XCTAssertEqual(model.isLoading, true)
+    fact.continuation.yield("0 is a good number.")
+    await task.value
+    XCTAssertEqual(model.fact, "0 is a good number.")
+    XCTAssertEqual(model.isLoading, false)
+  }
+}