Group tasks feature (#3)

This PR contains the work done to implement the **Group Task** feature, and to integrate it into the main content view of the app. Furthermore, an issue related to triggering a view update after inserting the todo tasks into the model container has been fixed.

Reviewed-on: rock-n-code/todos-app#3
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

UnitTests/Tests/View Models/ContentViewModelTests.swift

@@ -4,7 +4,7 @@ import Testing
 
 @testable import Todos
 
-@Suite("ContentView.ViewModel Tests")
+@Suite("ContentView view model tests")
 struct ContentViewModelTests {
 
     // MARK: Initialization Tests

UnitTests/Tests/View Models/NewTaskViewModelTests.swift

@@ -4,7 +4,7 @@ import Testing
 
 @testable import Todos
 
-@Suite("NewTaskView ViewModel Tests")
+@Suite("NewTaskView view model tests")
 struct NewTaskViewModelTests {
 
     // MARK: Initialization tests

UnitTests/Tests/View Models/TaskGroupListViewModelTests.swift

@@ -0,0 +1,82 @@
+import Foundation
+import SwiftData
+import Testing
+
+@testable import Todos
+
+@Suite("TaskGroupListView view model tests")
+struct TaskGroupListViewModelTests {
+
+    // MARK: Properties
+
+    private let calendar: Calendar = .current
+
+    // MARK: Computed tests
+
+    @Test("groups returns cases in predetermined order")
+    func groups() {
+        // GIVEN
+        let viewModel = TaskGroupListView.ViewModel()
+
+        // WHEN
+        let groups = viewModel.groups
+
+        // THEN
+        #expect(groups.count == 4)
+        #expect(groups[0] == .today)
+        #expect(groups[1] == .upcoming)
+        #expect(groups[2] == .overdue)
+        #expect(groups[3] == .completed)
+    }
+
+    // MARK: Functions tests
+
+    @Test(
+        "count returns zero when empty data",
+        arguments: TodoGroup.allCases
+    )
+    func countWhenEmptyData(for group: TodoGroup) throws {
+        // GIVEN
+        let tasks: [Todo] = []
+        let viewModel = TaskGroupListView.ViewModel()
+
+        // WHEN
+        let count = viewModel.count(tasks, for: group)
+
+        // THEN
+        #expect(count == 0)
+    }
+
+    @Test(
+        "count returns correct count when filled data",
+        arguments: TodoGroup.allCases
+    )
+    func countWhenFilledData(for group: TodoGroup) throws {
+        // GIVEN
+        let today: Date = .now
+        let tomorrow = calendar.date(byAdding: .day, value: 1, to: today) ?? today
+        let yesterday = calendar.date(byAdding: .day, value: -1, to: today) ?? today
+        let nextWeek = calendar.date(byAdding: .day, value: 7, to: today) ?? today
+        let lastWeek = calendar.date(byAdding: .day, value: -7, to: today) ?? today
+
+        let tasks = [
+            Todo(title: "Today task #1", due: today),
+            Todo(title: "Today task #2", due: today),
+            Todo(title: "Tomorrow task #1", due: tomorrow),
+            Todo(title: "Next week task #1", due: nextWeek),
+            Todo(title: "Yesterday task #1", due: yesterday),
+            Todo(title: "Last week task #1", due: lastWeek),
+            Todo(title: "Completed task #1", due: tomorrow, completed: today),
+            Todo(title: "Completed task #2", due: yesterday, completed: today)
+        ]
+
+        let viewModel = TaskGroupListView.ViewModel()
+
+        // WHEN
+        let count = viewModel.count(tasks, for: group)
+
+        // THEN
+        #expect(count == 2)
+    }
+
+}