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/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 context = container.mainContext
+        let repository = MockTodoRepository()
         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 todos = try context.fetch(descriptor)
-        let todo = try #require(todos.first)
+        let todo = try #require(repository.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 context = container.mainContext
+        let repository = MockTodoRepository()
         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 todos = try context.fetch(descriptor)
-        let todo = try #require(todos.first)
+        let todo = try #require(repository.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 context = container.mainContext
+        let repository = MockTodoRepository()
         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 todos = try context.fetch(descriptor)
-        let todo = try #require(todos.first)
+        let todo = try #require(repository.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() throws {
+    func saveMultipleTodos() {
         // GIVEN
-        let container = try modelContainer
-        let context = container.mainContext
+        let repository = MockTodoRepository()
         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>()
-        let todos = try context.fetch(descriptor)
-
-        #expect(todos.count == 2)
-        #expect(todos.contains { $0.title == "First task" })
-        #expect(todos.contains { $0.title == "Second task" })
+        #expect(repository.todos.count == 2)
+        #expect(repository.todos.contains { $0.title == "First task" })
+        #expect(repository.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)
-            )
-        }
-    }
-    
-}