Fixed issues encountered in the unit tests target after the project transitioned to Swift 6 and strict concurrency.

UnitTests/Tests/View Models/TaskListViewModelTests.swift

@@ -3,6 +3,7 @@ import Testing
 
 @testable import Todos
 
+@MainActor
 @Suite("TaskList view model tests")
 struct TaskListViewModelTests {
 
@@ -10,7 +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
@@ -26,7 +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,
@@ -54,7 +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]
         )
     )
@@ -74,7 +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