Todo repository protocol (#8)

This PR contains the work done to decouple the direct use of the `ModelContext` from `SwiftData` from the view model that uses it. In addition, the project transitioned to use Swift 6 and strict concurrency which brought some issues with the unit tests, so they were amended as well.

Reviewed-on: rock-n-code/todos-app#8
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

App/Sources/Extensions/ModelContext+Conformances.swift

@@ -0,0 +1,12 @@
+import SwiftData
+
+/// Extends ModelContext to conform to the TodoRepository protocol.
+///
+/// This extension allows ModelContext from SwiftData to be used as a todo repository,
+/// enabling dependency injection and facilitating unit testing by allowing mock
+/// repositories to be substituted during tests.
+///
+/// The ModelContext methods `delete(_:)` and `insert(_:)` already match the
+/// TodoRepository protocol requirements, so this extension simply declares conformance
+/// without requiring additional implementation.
+extension ModelContext: TodoRepository {}

App/Sources/Protocols/TodoRepository.swift

@@ -0,0 +1,28 @@
+import SwiftData
+
+/// A protocol defining the interface for a todo repository.
+///
+/// This protocol abstracts the underlying data persistence mechanism for todo tasks,
+/// allowing for dependency injection and easier testing. Implementations handle the
+/// storage and retrieval of Todo objects.
+protocol TodoRepository {
+
+    /// Deletes a todo task from the repository.
+    ///
+    /// This method removes the specified todo from persistent storage. The deletion
+    /// is typically performed immediately, though the actual persistence may be deferred
+    /// until a save operation occurs depending on the implementation.
+    ///
+    /// - Parameter todo: The todo task to delete from the repository.
+    func delete(_ todo: Todo)
+
+    /// Inserts a new todo task into the repository.
+    ///
+    /// This method adds a new todo to persistent storage. The todo is typically
+    /// tracked immediately, though the actual persistence may be deferred until a
+    /// save operation occurs depending on the implementation.
+    ///
+    /// - Parameter todo: The todo task to insert into the repository.
+    func insert(_ todo: Todo)
+
+}

App/Sources/View Models/NewTaskViewModel.swift

@@ -57,14 +57,14 @@ extension NewTaskView {
 
         // MARK: Functions
 
-        /// Saves a new todo task to the SwiftData model context.
+        /// Saves a new todo task to the repository.
         ///
-        /// This function creates a new `Todo` instance with the current property values and inserts it into the provided model context.
+        /// This function creates a new `Todo` instance with the current property values and inserts it into the provided repository.
         /// The title and note are trimmed of leading and trailing whitespace before saving.
         /// The `note` property value is only included if it's not empty after trimming.
         ///
-        /// - Parameter modelContext: The SwiftData model context to insert a new todo task.
+        /// - Parameter repository: The repository to insert a new todo task.
-        func save(to modelContext: ModelContext) {
+        func save(to repository: TodoRepository) {
             let trimmedTitle = title.trimmingCharacters(in: .whitespacesAndNewlines)
             let trimmedNote = note.trimmingCharacters(in: .whitespacesAndNewlines)
 
@@ -74,7 +74,7 @@ extension NewTaskView {
                 due: due
             )
 
-            modelContext.insert(todo)
+            repository.insert(todo)
         }
 
     }

App/Sources/View Models/TaskListViewModel.swift

@@ -87,21 +87,21 @@ extension TaskListView {
 
         /// Deletes tasks at the specified indices.
         ///
-        /// This method removes tasks from the model context after a swipe-to-delete action.
+        /// This method removes tasks from the repository after a swipe-to-delete action.
-        /// The deletion is performed through SwiftData's model context, which handles
+        /// The deletion is performed through the repository, which handles
         /// persistence and triggers automatic UI updates.
         ///
         /// - Parameters:
         ///   - tasks: The current array of tasks.
         ///   - offsets: The index set of tasks to delete.
-        ///   - modelContext: The SwiftData model context to perform the deletion.
+        ///   - repository: The repository to perform the deletion.
-        func deleteTasks(
+        func delete(
             _ tasks: [Todo],
             at offsets: IndexSet,
-            from modelContext: ModelContext
+            from repository: TodoRepository
         ) {
             for index in offsets {
-                modelContext.delete(tasks[index])
+                repository.delete(tasks[index])
             }
         }
 

App/Sources/Views/TaskListView.swift

@@ -45,7 +45,7 @@ struct TaskListView: View {
             group: viewModel.group,
             showCompleted: viewModel.showCompleted
         ) { tasks, offsets in
-            viewModel.deleteTasks(
+            viewModel.delete(
                 tasks,
                 at: offsets,
                 from: modelContext

Todos.xcodeproj/project.pbxproj

@@ -410,8 +410,9 @@
 				SWIFT_APPROACHABLE_CONCURRENCY = YES;
 				SWIFT_DEFAULT_ACTOR_ISOLATION = MainActor;
 				SWIFT_EMIT_LOC_STRINGS = YES;
+				SWIFT_STRICT_CONCURRENCY = complete;
 				SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TARGETED_DEVICE_FAMILY = "1,2,7";
 				XROS_DEPLOYMENT_TARGET = 26.0;
 			};
@@ -456,8 +457,9 @@
 				SWIFT_APPROACHABLE_CONCURRENCY = YES;
 				SWIFT_DEFAULT_ACTOR_ISOLATION = MainActor;
 				SWIFT_EMIT_LOC_STRINGS = YES;
+				SWIFT_STRICT_CONCURRENCY = complete;
 				SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TARGETED_DEVICE_FAMILY = "1,2,7";
 				XROS_DEPLOYMENT_TARGET = 26.0;
 			};

UnitTests/Mocks/MockTodoRepository.swift

@@ -0,0 +1,49 @@
+@testable import class Todos.Todo
+@testable import protocol Todos.TodoRepository
+
+/// A mock implementation of the TodoRepository protocol for unit testing.
+///
+/// This mock repository provides a simple in-memory storage mechanism for testing
+/// without requiring a full SwiftData ModelContext setup. It tracks inserted and
+/// deleted todos, allowing tests to verify repository operations.
+final class MockTodoRepository {
+
+    // MARK: Properties
+
+    /// Array of todo tasks managed by this mock repository.
+    ///
+    /// This property tracks all todos in the repository, maintaining state across
+    /// insert and delete operations. It serves as the in-memory storage for the mock,
+    /// allowing tests to verify repository behavior without requiring SwiftData.
+    private(set) var todos: [Todo]
+
+    // MARK: Initializers
+
+    /// Creates a new mock repository with an optional initial set of todo tasks.
+    ///
+    /// This initializer allows tests to set up a repository with pre-existing todos
+    /// or start with an empty repository. The default parameter value provides
+    /// convenient initialization for most test cases.
+    ///
+    /// - Parameter todos: An array of todo tasks to initialize the repository with. Defaults to an empty array.
+    init(todos: [Todo] = []) {
+        self.todos = todos
+    }
+
+}
+
+// MARK: - TodoRepository
+
+extension MockTodoRepository: TodoRepository {
+
+    // MARK: Functions
+
+    func delete(_ todo: Todo) {
+        todos.removeAll { $0.id == todo.id }
+    }
+
+    func insert(_ todo: Todo) {
+        todos.append(todo)
+    }
+
+}

UnitTests/Tests/Enumerations/TodoGroupTests.swift

@@ -1,9 +1,9 @@
-import Foundation
 import SwiftUI
 import Testing
 
 @testable import Todos
 
+@MainActor
 @Suite("TodoGroup enumeration tests")
 struct TodoGroupTests {
 
@@ -12,7 +12,7 @@ struct TodoGroupTests {
     @Test(
         "canShowCompleted returns correct values",
         arguments: zip(
-            TodoGroup.allCases,
+            [TodoGroup.today, .upcoming, .overdue, .completed],
             [true, true, true, false]
         )
     )
@@ -31,7 +31,7 @@ struct TodoGroupTests {
     @Test(
         "canReorder returns correct values",
         arguments: zip(
-            TodoGroup.allCases,
+            [TodoGroup.today, .upcoming, .overdue, .completed],
             [true, true, true, false]
         )
     )
@@ -50,7 +50,7 @@ struct TodoGroupTests {
     @Test(
         "group color match expected values",
         arguments: zip(
-            TodoGroup.allCases,
+            [TodoGroup.today, .upcoming, .overdue, .completed],
             [Color.blue, .green, .red, .gray]
         )
     )
@@ -69,7 +69,7 @@ struct TodoGroupTests {
     @Test(
         "group icon names match expected values",
         arguments: zip(
-            TodoGroup.allCases,
+            [TodoGroup.today, .upcoming, .overdue, .completed],
             ["calendar.badge.clock", "calendar", "calendar.badge.exclamationmark", "checkmark.circle.fill"]
         )
     )
@@ -88,7 +88,7 @@ struct TodoGroupTests {
     @Test(
         "group titles match expected values",
         arguments: zip(
-            TodoGroup.allCases,
+            [TodoGroup.today, .upcoming, .overdue, .completed],
             ["today", "upcoming", "overdue", "completed"]
         )
     )
@@ -124,7 +124,10 @@ struct TodoGroupTests {
 
     // MARK: Identifiable Tests
 
-    @Test("id returns an identity of a case", arguments: TodoGroup.allCases)
+    @Test(
+        "id returns an identity of a case",
+        arguments: [TodoGroup.today, .upcoming, .overdue, .completed]
+    )
     func id(for group: TodoGroup) {
         // GIVEN
         // WHEN

UnitTests/Tests/Extensions/TodoFetchDescriptor+InitsTests.swift

@@ -4,6 +4,7 @@ import Testing
 
 @testable import Todos
 
+@MainActor
 @Suite("TodoFetchDescriptor+Inits extension tests")
 struct TodoFetchDescriptor_InitsTests {
 
@@ -11,9 +12,8 @@ struct TodoFetchDescriptor_InitsTests {
 
     @Test(
         "initialization when empty tasks",
-        arguments: TodoGroup.allCases
+        arguments: [TodoGroup.today, .upcoming, .overdue, .completed]
     )
-    @MainActor
     func initializationWhenEmptyTasks(for group: TodoGroup) throws {
         // GIVEN
         let container = try modelContainer
@@ -32,9 +32,8 @@ struct TodoFetchDescriptor_InitsTests {
 
     @Test(
         "initialization with show completed disabled",
-        arguments: TodoGroup.allCases
+        arguments: [TodoGroup.today, .upcoming, .overdue, .completed]
     )
-    @MainActor
     func initializationWithNoShowCompleted(for group: TodoGroup) throws {
         // GIVEN
         let container = try modelContainer
@@ -70,9 +69,8 @@ struct TodoFetchDescriptor_InitsTests {
 
     @Test(
         "initialization with show completed enabled",
-        arguments: TodoGroup.allCases
+        arguments: [TodoGroup.today, .upcoming, .overdue, .completed]
     )
-    @MainActor
     func initializationWithShowCompleted(for group: TodoGroup) throws {
         // GIVEN
         let container = try modelContainer

UnitTests/Tests/View Models/ContentViewModelTests.swift

@@ -1,9 +1,8 @@
-import Foundation
-import SwiftData
 import Testing
 
 @testable import Todos
 
+@MainActor
 @Suite("ContentView view model tests")
 struct ContentViewModelTests {
 

UnitTests/Tests/View Models/NewTaskViewModelTests.swift

@@ -1,9 +1,9 @@
 import Foundation
-import SwiftData
 import Testing
 
 @testable import Todos
 
+@MainActor
 @Suite("NewTaskView view model tests")
 struct NewTaskViewModelTests {
 
@@ -121,11 +121,9 @@ struct NewTaskViewModelTests {
     // MARK: Functions tests
 
     @Test("save creates todo with all properties")
-    @MainActor
     func saveWithAllProperties() throws {
         // GIVEN
-        let container = try modelContainer
+        let repository = MockTodoRepository()
-        let context = container.mainContext
         let viewModel = NewTaskView.ViewModel()
 
         // WHEN
@@ -133,12 +131,10 @@ struct NewTaskViewModelTests {
         viewModel.note = "Finish by end of week"
         viewModel.due = Date(timeIntervalSince1970: 1000000000)
 
-        viewModel.save(to: context)
+        viewModel.save(to: repository)
 
         // THEN
-        let descriptor = FetchDescriptor<Todo>()
+        let todo = try #require(repository.todos.first)
-        let todos = try context.fetch(descriptor)
-        let todo = try #require(todos.first)
 
         #expect(todo.title == viewModel.title)
         #expect(todo.note == viewModel.note)
@@ -147,11 +143,9 @@ struct NewTaskViewModelTests {
     }
 
     @Test("save creates todo without note when note is empty")
-    @MainActor
     func saveWithEmptyNote() throws {
         // GIVEN
-        let container = try modelContainer
+        let repository = MockTodoRepository()
-        let context = container.mainContext
         let viewModel = NewTaskView.ViewModel()
 
         // WHEN
@@ -159,12 +153,10 @@ struct NewTaskViewModelTests {
         viewModel.note = ""
         viewModel.due = Date()
 
-        viewModel.save(to: context)
+        viewModel.save(to: repository)
 
         // THEN
-        let descriptor = FetchDescriptor<Todo>()
+        let todo = try #require(repository.todos.first)
-        let todos = try context.fetch(descriptor)
-        let todo = try #require(todos.first)
 
         #expect(todo.title == viewModel.title)
         #expect(todo.note == nil)
@@ -173,11 +165,9 @@ struct NewTaskViewModelTests {
     }
 
     @Test("save creates todo with note containing only whitespace as nil")
-    @MainActor
     func saveWithWhitespaceNote() throws {
         // GIVEN
-        let container = try modelContainer
+        let repository = MockTodoRepository()
-        let context = container.mainContext
         let viewModel = NewTaskView.ViewModel()
 
         // WHEN
@@ -185,12 +175,10 @@ struct NewTaskViewModelTests {
         viewModel.note = "   "
         viewModel.due = Date()
 
-        viewModel.save(to: context)
+        viewModel.save(to: repository)
 
         // THEN
-        let descriptor = FetchDescriptor<Todo>()
+        let todo = try #require(repository.todos.first)
-        let todos = try context.fetch(descriptor)
-        let todo = try #require(todos.first)
 
         #expect(todo.title == viewModel.title)
         #expect(todo.note == nil)
@@ -199,46 +187,24 @@ struct NewTaskViewModelTests {
     }
 
     @Test("save inserts multiple todos independently")
-    @MainActor
+    func saveMultipleTodos() {
-    func saveMultipleTodos() throws {
         // GIVEN
-        let container = try modelContainer
+        let repository = MockTodoRepository()
-        let context = container.mainContext
         let viewModelFirst = NewTaskView.ViewModel()
         let viewModelSecond = NewTaskView.ViewModel()
 
         // WHEN
         viewModelFirst.title = "First task"
-        viewModelFirst.save(to: context)
+        viewModelFirst.save(to: repository)
 
         viewModelSecond.title = "Second task"
         viewModelSecond.note = "With a note"
-        viewModelSecond.save(to: context)
+        viewModelSecond.save(to: repository)
 
         // THEN
-        let descriptor = FetchDescriptor<Todo>()
+        #expect(repository.todos.count == 2)
-        let todos = try context.fetch(descriptor)
+        #expect(repository.todos.contains { $0.title == "First task" })
-
+        #expect(repository.todos.contains { $0.title == "Second task" })
-        #expect(todos.count == 2)
-        #expect(todos.contains { $0.title == "First task" })
-        #expect(todos.contains { $0.title == "Second task" })
-    }
-
-}
-
-// MARK: - Helpers
-
-private extension NewTaskViewModelTests {
-    
-    // MARK: Computed
-    
-    var modelContainer: ModelContainer {
-        get throws {
-            try ModelContainer(
-                for: Todo.self,
-                configurations: .init(isStoredInMemoryOnly: true)
-            )
-        }
     }
 
 }

UnitTests/Tests/View Models/TaskGroupListViewModelTests.swift

@@ -1,9 +1,9 @@
 import Foundation
-import SwiftData
 import Testing
 
 @testable import Todos
 
+@MainActor
 @Suite("TaskGroupListView view model tests")
 struct TaskGroupListViewModelTests {
 
@@ -33,7 +33,7 @@ struct TaskGroupListViewModelTests {
 
     @Test(
         "count returns zero when empty data",
-        arguments: TodoGroup.allCases
+        arguments: [TodoGroup.today, .upcoming, .overdue, .completed]
     )
     func countWhenEmptyData(for group: TodoGroup) throws {
         // GIVEN
@@ -48,7 +48,7 @@ struct TaskGroupListViewModelTests {
 
     @Test(
         "count returns correct count when filled data",
-        arguments: TodoGroup.allCases
+        arguments: [TodoGroup.today, .upcoming, .overdue, .completed]
     )
     func countWhenFilledData(for group: TodoGroup) throws {
         // GIVEN

UnitTests/Tests/View Models/TaskListViewModelTests.swift

@@ -1,10 +1,9 @@
-import Foundation
-import SwiftData
 import SwiftUI
 import Testing
 
 @testable import Todos
 
+@MainActor
 @Suite("TaskList view model tests")
 struct TaskListViewModelTests {
 
@@ -12,7 +11,7 @@ struct TaskListViewModelTests {
 
     @Test(
         "properties are set correctly during initialization",
-        arguments: TodoGroup.allCases
+        arguments: [TodoGroup.today, .upcoming, .overdue, .completed]
     )
     func initialization(for group: TodoGroup) {
         // GIVEN
@@ -28,7 +27,7 @@ struct TaskListViewModelTests {
 
     @Test(
         "buttonCompleted returns correct values when showCompleted is true",
-        arguments: TodoGroup.allCases, [true, false]
+        arguments: [TodoGroup.today, .upcoming, .overdue, .completed], [true, false]
     )
     func buttonCompleted(
         for group: TodoGroup,
@@ -56,7 +55,7 @@ struct TaskListViewModelTests {
     @Test(
         "canShowCompleted returns correct value for each group",
         arguments: zip(
-            TodoGroup.allCases,
+            [TodoGroup.today, .upcoming, .overdue, .completed],
             [true, true, true, false]
         )
     )
@@ -76,7 +75,7 @@ struct TaskListViewModelTests {
 
     @Test(
         "navigationTitle returns correct view title for each group",
-        arguments: TodoGroup.allCases
+        arguments: [TodoGroup.today, .upcoming, .overdue, .completed]
     )
     func navigationTitle(for group: TodoGroup) {
         // GIVEN
@@ -91,43 +90,59 @@ struct TaskListViewModelTests {
 
     // MARK: Method tests
 
-    @Test("deleteTasks removes a single task from model context")
+    @Test("delete removes a single todo task from repository")
-    func deleteTasksSingle() throws {
+    func deleteSingleTodo() {
         // GIVEN
-        let container = try ModelContainer(
+        let todos: [Todo] = [
-            for: Todo.self,
-            configurations: .init(isStoredInMemoryOnly: true)
-        )
-        let context = ModelContext(container)
-
-        let viewModel = TaskListView.ViewModel(group: .today)
-        let todosToInsert: [Todo] = [
             .init(title: "Task 1", due: .now, order: 0),
             .init(title: "Task 2", due: .now, order: 1),
             .init(title: "Task 3", due: .now, order: 2),
         ]
-        let countInitial = todosToInsert.count
+        let repository = MockTodoRepository(todos: todos)
-
+        let viewModel = TaskListView.ViewModel(group: .today)
-        for todo in todosToInsert {
-            context.insert(todo)
-        }
 
         // WHEN
-        viewModel.deleteTasks(
+        viewModel.delete(
-            todosToInsert,
+            todos,
             at: IndexSet(integer: 1),
-            from: context
+            from: repository
         )
 
         // THEN
-        let descriptor = FetchDescriptor<Todo>()
+        #expect(repository.todos.count == 2)
-        let todos = try context.fetch(descriptor)
+        #expect(repository.todos.contains { $0.title == "Task 1" })
+        #expect(repository.todos.contains { $0.title == "Task 3" })
+        #expect(!repository.todos.contains { $0.title == "Task 2" })
+    }
 
-        #expect(countInitial == 3)
+    @Test("delete removes multiple todo tasks from repository")
-        #expect(todos.count == 2)
+    func deleteMultipleTodos() {
-        #expect(todos.contains(where: { $0.title == "Task 1" }))
+        // GIVEN
-        #expect(todos.contains(where: { $0.title == "Task 3" }))
+        let todos: [Todo] = [
-        #expect(!todos.contains(where: { $0.title == "Task 2" }))
+            .init(title: "Task 1", due: .now, order: 0),
+            .init(title: "Task 2", due: .now, order: 1),
+            .init(title: "Task 3", due: .now, order: 2),
+            .init(title: "Task 4", due: .now, order: 3),
+            .init(title: "Task 5", due: .now, order: 4),
+        ]
+        
+        let repository = MockTodoRepository(todos: todos)
+        let viewModel = TaskListView.ViewModel(group: .today)
+
+        // WHEN
+        viewModel.delete(
+            todos,
+            at: IndexSet([1, 3]),
+            from: repository
+        )
+
+        // THEN
+        #expect(repository.todos.count == 3)
+        #expect(repository.todos.contains { $0.title == "Task 1" })
+        #expect(repository.todos.contains { $0.title == "Task 3" })
+        #expect(repository.todos.contains { $0.title == "Task 5" })
+        #expect(!repository.todos.contains { $0.title == "Task 2" })
+        #expect(!repository.todos.contains { $0.title == "Task 4" })
     }
 
     @Test("reorderTasks updates order property when moving task forward")
@@ -180,7 +195,7 @@ struct TaskListViewModelTests {
         #expect(tasks[3].order == 1)
     }
 
-    @Test("toggleCompletedVisbility toggles the showCompleted property")
+    @Test("toggleCompletedVisibility toggles the showCompleted property")
     func toggleCompletedVisibility() {
         // GIVEN
         let viewModel = TaskListView.ViewModel(group: .today)