OverviewVM LoadData test with DI

OverviewVMTests.cs

    public async Task LoadData_loads_data_from_repository()
    {
        // Arrange
        OverviewVM vm = new OverviewVM(new MockRepository());

        // Act
        await vm.LoadData();

        // Assert
        Assert.That(vm.ToDoItems.Count(), Is.EqualTo(3));
    }