Avoid failure when setting test dependency values (#1570)

* Avoid failure when setting test dependency values

It's currently possible to emit XCTest failures when testing reducers
that access dependency values that emit failure upon access, which
includes the calendar, locale, time zone, and URL session dependencies.

We may need a more holistic solution for folks that define these kinds
of dependencies outside the library, but this will make the
library-level failures a bit more lenient.

* wip

* a few more tests

Co-authored-by: Brandon Williams <[email protected]>
(cherry picked from commit f8554f7088e344b8e4d598648c8fb758a378dcb3)

# Conflicts:
#	Tests/ComposableArchitectureTests/StoreTests.swift
#	Tests/ComposableArchitectureTests/TestStoreTests.swift

Author: stephencelis

Examples/TicTacToe/tic-tac-toe/Sources/AuthenticationClient/AuthenticationClient.swift

@@ -72,7 +72,7 @@ public struct AuthenticationClient: Sendable {
 }
 
 extension AuthenticationClient: TestDependencyKey {
-  public static var testValue = Self(
+  public static let testValue = Self(
     login: unimplemented("\(Self.self).login"),
     twoFactor: unimplemented("\(Self.self).twoFactor")
   )

Sources/Dependencies/Dependencies/Calendar.swift

@@ -33,7 +33,9 @@ extension DependencyValues {
   private enum CalendarKey: DependencyKey {
     static let liveValue = Calendar.autoupdatingCurrent
     static var testValue: Calendar {
-      XCTFail(#"Unimplemented: @Dependency(\.calendar)"#)
+      if !DependencyValues.isSetting {
+        XCTFail(#"Unimplemented: @Dependency(\.calendar)"#)
+      }
       return .autoupdatingCurrent
     }
   }

Sources/Dependencies/Dependencies/Locale.swift

@@ -45,7 +45,9 @@ extension DependencyValues {
   private enum LocaleKey: DependencyKey {
     static let liveValue = Locale.autoupdatingCurrent
     static var testValue: Locale {
-      XCTFail(#"Unimplemented: @Dependency(\.locale)"#)
+      if !DependencyValues.isSetting {
+        XCTFail(#"Unimplemented: @Dependency(\.locale)"#)
+      }
       return .autoupdatingCurrent
     }
   }

Sources/Dependencies/Dependencies/TimeZone.swift

@@ -24,7 +24,9 @@ extension DependencyValues {
   private enum TimeZoneKey: DependencyKey {
     static let liveValue = TimeZone.autoupdatingCurrent
     static var testValue: TimeZone {
-      XCTFail(#"Unimplemented: @Dependency(\.timeZone)"#)
+      if !DependencyValues.isSetting {
+        XCTFail(#"Unimplemented: @Dependency(\.timeZone)"#)
+      }
       return .autoupdatingCurrent
     }
   }

Sources/Dependencies/Dependencies/URLSession.swift

@@ -79,7 +79,9 @@ extension DependencyValues {
   private enum URLSessionKey: DependencyKey {
     static let liveValue = URLSession.shared
     static var testValue: URLSession {
-      XCTFail(#"Unimplemented: @Dependency(\.urlSession)"#)
+      if !DependencyValues.isSetting {
+        XCTFail(#"Unimplemented: @Dependency(\.urlSession)"#)
+      }
       let configuration = URLSessionConfiguration.ephemeral
       configuration.protocolClasses = [UnimplementedURLProtocol.self]
       return URLSession(configuration: configuration)

Sources/Dependencies/DependencyValues.swift

@@ -55,7 +55,7 @@ import XCTestDynamicOverlay
 /// ```
 public struct DependencyValues: Sendable {
   @TaskLocal public static var _current = Self()
-  @TaskLocal fileprivate static var isSetting = false
+  @TaskLocal static var isSetting = false
   @TaskLocal static var currentDependency = CurrentDependency()
 
   private var cachedValues = CachedValues()