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>

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")
-    func deleteTasksSingle() throws {
+    @Test("delete removes a single todo task from repository")
+    func deleteSingleTodo() {
         // GIVEN
-        let container = try ModelContainer(
-            for: Todo.self,
-            configurations: .init(isStoredInMemoryOnly: true)
-        )
-        let context = ModelContext(container)
-
-        let viewModel = TaskListView.ViewModel(group: .today)
-        let todosToInsert: [Todo] = [
+        let todos: [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
-
-        for todo in todosToInsert {
-            context.insert(todo)
-        }
+        let repository = MockTodoRepository(todos: todos)
+        let viewModel = TaskListView.ViewModel(group: .today)
 
         // WHEN
-        viewModel.deleteTasks(
-            todosToInsert,
+        viewModel.delete(
+            todos,
             at: IndexSet(integer: 1),
-            from: context
+            from: repository
         )
 
         // THEN
-        let descriptor = FetchDescriptor<Todo>()
-        let todos = try context.fetch(descriptor)
+        #expect(repository.todos.count == 2)
+        #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)
-        #expect(todos.count == 2)
-        #expect(todos.contains(where: { $0.title == "Task 1" }))
-        #expect(todos.contains(where: { $0.title == "Task 3" }))
-        #expect(!todos.contains(where: { $0.title == "Task 2" }))
+    @Test("delete removes multiple todo tasks from repository")
+    func deleteMultipleTodos() {
+        // GIVEN
+        let todos: [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),
+            .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)