public async Task DeleteAllAsync_Should_DeleteAllTodos()
{
//Setup DbContext and DbSet mock
var dbContextMock = new Mock <ITodoContext>();
var testTodos = GetTestTodos();
var todoDbSetMock = testTodos.AsQueryable().GetMockDbSet();
dbContextMock.Setup(x => x.DbSet <Todo>()).Returns(todoDbSetMock.Object);
//Execute
var todoService = new TodoService(dbContextMock.Object);
var todosBefore = await todoService.GetAllAsync <Todo>();
await todoService.DeleteAllAsync <Todo>();
var todosAfter = await todoService.GetAllAsync <Todo>();
//Assert
Assert.IsAssignableFrom <IEnumerable <Todo> >(todosBefore);
Assert.NotNull(todosBefore);
Assert.Empty(todosAfter);
}