Add a few missing tests

Tests/ComposableArchitectureTests/EffectFailureTests.swift

@@ -13,9 +13,7 @@
       var line: UInt!
       XCTExpectFailure {
         $0.compactDescription == """
-          An "EffectTask.task" returned from \
-          "ComposableArchitectureTests/EffectFailureTests.swift:\(line+1)" threw an unhandled \
-          error. …
+          An "EffectTask.task" returned from "\(#fileID):\(line+1)" threw an unhandled error. …
 
               EffectFailureTests.Unexpected()
 
@@ -39,9 +37,7 @@
       var line: UInt!
       XCTExpectFailure {
         $0.compactDescription == """
-          An "EffectTask.run" returned from \
-          "ComposableArchitectureTests/EffectFailureTests.swift:\(line+1)" threw an unhandled \
-          error. …
+          An "EffectTask.run" returned from "\(#fileID):\(line+1)" threw an unhandled error. …
 
               EffectFailureTests.Unexpected()
 

Tests/ComposableArchitectureTests/EffectRunTests.swift

@@ -46,8 +46,7 @@ final class EffectRunTests: XCTestCase {
       var line: UInt!
       XCTExpectFailure(nil, enabled: nil, strict: nil) {
         $0.compactDescription == """
-          An "EffectTask.run" returned from \
-          "ComposableArchitectureTests/EffectRunTests.swift:\(line+1)" threw an unhandled error. …
+          An "EffectTask.run" returned from "\(#fileID):\(line+1)" threw an unhandled error. …
 
               EffectRunTests.Failure()
 

Tests/ComposableArchitectureTests/EffectTaskTests.swift

@@ -46,8 +46,7 @@ final class EffectTaskTests: XCTestCase {
       var line: UInt!
       XCTExpectFailure(nil, enabled: nil, strict: nil) {
         $0.compactDescription == """
-          An "EffectTask.task" returned from \
-          "ComposableArchitectureTests/EffectTaskTests.swift:\(line+1)" threw an unhandled error. …
+          An "EffectTask.task" returned from "\(#fileID):\(line+1)" threw an unhandled error. …
 
               EffectTaskTests.Failure()
 

Tests/ComposableArchitectureTests/ForEachReducerTests.swift

@@ -0,0 +1,99 @@
+import ComposableArchitecture
+import XCTest
+
+@MainActor
+final class ForEachReducerTests: XCTestCase {
+  func testElementAction() async {
+    let store = TestStore(
+      initialState: Elements.State(
+        rows: [
+          .init(id: 1, value: "Blob"),
+          .init(id: 2, value: "Blob Jr."),
+          .init(id: 3, value: "Blob Sr."),
+        ]
+      ),
+      reducer: Elements()
+    )
+
+    await store.send(.row(id: 1, action: "Blob Esq.")) {
+      $0.rows[id: 1]?.value = "Blob Esq."
+    }
+    await store.send(.row(id: 2, action: "")) {
+      $0.rows[id: 2]?.value = ""
+    }
+    await store.receive(.row(id: 2, action: "Empty")) {
+      $0.rows[id: 2]?.value = "Empty"
+    }
+  }
+
+  func testNonElementAction() async {
+    let store = TestStore(
+      initialState: Elements.State(),
+      reducer: Elements()
+    )
+
+    await store.send(.buttonTapped)
+  }
+
+  #if DEBUG
+    func testMissingElement() async {
+      let store = TestStore(
+        initialState: Elements.State(),
+        reducer: EmptyReducer()
+          .forEach(\.rows, action: /Elements.Action.row) {}
+      )
+
+      XCTExpectFailure {
+        $0.compactDescription == """
+          A "forEach" at "\(#fileID):\(#line - 5)" received an action for a missing element.
+
+            Action:
+              Elements.Action.row(id:, action:)
+
+          This is generally considered an application logic error, and can happen for a few reasons:
+
+          • A parent reducer removed an element with this ID before this reducer ran. This reducer \
+          must run before any other reducer removes an element, which ensures that element reducers \
+          can handle their actions while their state is still available.
+
+          • An in-flight effect emitted this action when state contained no element at this ID. \
+          While it may be perfectly reasonable to ignore this action, consider canceling the \
+          associated effect before an element is removed, especially if it is a long-living effect.
+
+          • This action was sent to the store while its state contained no element at this ID. To \
+          fix this make sure that actions for this reducer can only be sent from a view store when \
+          its state contains an element at this id. In SwiftUI applications, use "ForEachStore".
+          """
+      }
+
+      await store.send(.row(id: 1, action: "Blob Esq."))
+    }
+  #endif
+}
+
+struct Elements: ReducerProtocol {
+  struct State: Equatable {
+    struct Row: Equatable, Identifiable {
+      var id: Int
+      var value: String
+    }
+    var rows: IdentifiedArrayOf<Row> = []
+  }
+  enum Action: Equatable {
+    case buttonTapped
+    case row(id: Int, action: String)
+  }
+  var body: Reduce<State, Action> {
+    Reduce<State, Action> { state, action in
+      .none
+    }
+    .forEach(\.rows, action: /Action.row) {
+      Reduce { state, action in
+        state.value = action
+        return action.isEmpty
+          ? .run { await $0("Empty") }
+          : .none
+      }
+    }
+  }
+}

Tests/ComposableArchitectureTests/IfCaseLetReducerTests.swift

@@ -0,0 +1,73 @@
+import ComposableArchitecture
+import XCTest
+
+@MainActor
+final class IfCaseLetReducerTests: XCTestCase {
+  func testChildAction() async {
+    struct SomeError: Error, Equatable {}
+
+    let store = TestStore(
+      initialState: Result.success(0),
+      reducer: Reduce<Result<Int, SomeError>, Result<Int, SomeError>> { state, action in
+        .none
+      }
+      .ifCaseLet(/Result.success, action: /Result.success) {
+        Reduce { state, action in
+          state = action
+          return state < 0 ? .run { await $0(0) } : .none
+        }
+      }
+    )
+
+    await store.send(.success(1)) {
+      $0 = .success(1)
+    }
+    await store.send(.failure(SomeError()))
+    await store.send(.success(-1)) {
+      $0 = .success(-1)
+    }
+    await store.receive(.success(0)) {
+      $0 = .success(0)
+    }
+  }
+
+  #if DEBUG
+    func testNilChild() async {
+      struct SomeError: Error, Equatable {}
+
+      let store = TestStore(
+        initialState: Result.failure(SomeError()),
+        reducer: EmptyReducer<Result<Int, SomeError>, Result<Int, SomeError>>()
+          .ifCaseLet(/Result.success, action: /Result.success) {}
+      )
+
+      XCTExpectFailure {
+        $0.compactDescription == """
+          An "ifCaseLet" at "\(#fileID):\(#line - 5)" received a child action when child state was \
+          set to a different case. …
+
+            Action:
+              Result.success
+            State:
+              Result.failure
+
+          This is generally considered an application logic error, and can happen for a few reasons:
+
+          • A parent reducer set "Result" to a different case before this reducer ran. This reducer \
+          must run before any other reducer sets child state to a different case. This ensures that \
+          child reducers can handle their actions while their state is still available.
+
+          • An in-flight effect emitted this action when child state was unavailable. While it may \
+          be perfectly reasonable to ignore this action, consider canceling the associated effect \
+          before child state changes to another case, especially if it is a long-living effect.
+
+          • This action was sent to the store while state was another case. Make sure that actions \
+          for this reducer can only be sent from a view store when state is set to the appropriate \
+          case. In SwiftUI applications, use "SwitchStore".
+          """
+      }
+
+      await store.send(.success(1))
+    }
+  #endif
+}

Tests/ComposableArchitectureTests/IfLetReducerTests.swift

@@ -0,0 +1,41 @@
+import ComposableArchitecture
+import XCTest
+
+@MainActor
+final class IfLetReducerTests: XCTestCase {
+  #if DEBUG
+    func testNilChild() async {
+      let store = TestStore(
+        initialState: Int?.none,
+        reducer: EmptyReducer<Int?, Void>()
+          .ifLet(\.self, action: /.self) {}
+      )
+
+      XCTExpectFailure {
+        $0.compactDescription == """
+          An "ifLet" at "\(#fileID):\(#line - 5)" received a child action when child state was \
+          "nil". …
+
+            Action:
+              ()
+
+          This is generally considered an application logic error, and can happen for a few reasons:
+
+          • A parent reducer set child state to "nil" before this reducer ran. This reducer must run \
+          before any other reducer sets child state to "nil". This ensures that child reducers can \
+          handle their actions while their state is still available.
+
+          • An in-flight effect emitted this action when child state was "nil". While it may be \
+          perfectly reasonable to ignore this action, consider canceling the associated effect \
+          before child state becomes "nil", especially if it is a long-living effect.
+
+          • This action was sent to the store while state was "nil". Make sure that actions for this \
+          reducer can only be sent from a view store when state is non-"nil". In SwiftUI \
+          applications, use "IfLetStore".
+          """
+      }
+
+      await store.send(())
+    }
+  #endif
+}