Writing tests with Jasmine for vanilla JS

I followed Dev Eds course on creating a todo list, but now I want to write some tests to test the code. I want to use Jest but I'm not sure how to write a test to make sure that a todo is created, and deleted.

I've added the app.js file below (there is are html/css files as well). My attempt at writing a test is under the app.js file.

//Selectors
const todoInput = document.querySelector('.todo-input');
const todoButton = document.querySelector('.todo-button');
const todoList = document.querySelector('.todo-list');
const filterOption = document.querySelector('.filter-todo');

//Event Listeners
todoButton.addEventListener('click', addTodo);
todoList.addEventListener('click', deleteCheck);
filterOption.addEventListener('change', filterTodo);

//Functions
function addTodo(event){
    //console.log(event.target);
    // prevent form from submitting
    event.preventDefault();
    const todoDiv = document.createElement("div");
    todoDiv.classList.add("todo");
    //create LI
    const newTodo = document.createElement('li');
    newTodo.innerText = todoInput.value;
    newTodo.classList.add('todo-item');
    todoDiv.appendChild(newTodo);
    // Checkmark button
    const completedButton = document.createElement('button');
    completedButton.innerHTML = '<i class="fas fa-check"></i>'
    completedButton.classList.add("complete-btn");
    todoDiv.appendChild(completedButton);
    // Delete button
    const deleteButton = document.createElement('button');
    deleteButton.innerHTML = '<i class="fas fa-trash"></i>'
    deleteButton.classList.add("delete-btn");
    todoDiv.appendChild(deleteButton);
    // Append to list
    todoList.appendChild(todoDiv);
    // clear todo input value
    todoInput.value = "";
}

function deleteCheck(e){
    //console.log(e.target);
    const item = e.target;
    if(item.classList[0] === 'delete-btn'){
        const todo = item.parentElement;
        // animation
        todo.classList.add("fall");
        todo.addEventListener("transitionend", function() {
            todo.remove();
        });
    }
    // check mark
    if(item.classList[0] === "complete-btn"){
        const todo = item.parentElement;
        todo.classList.toggle('completed');
    }
}

function filterTodo(e) {
    const todos = todoList.childNodes;
    todos.forEach(function(todo) {
      switch (e.target.value) {
        case "all":
          todo.style.display = "flex";
          break;
        case "completed":
          if (todo.classList.contains("completed")) {
            todo.style.display = "flex";
          } else {
            todo.style.display = "none";
          }
          break;
        case "uncompleted":
          if (!todo.classList.contains("completed")) {
            todo.style.display = "flex";
          } else {
            todo.style.display = "none";
          }
      }
    });
  }

The first test I created was to check if a todo is created

const todo = require('./app')

test('add a todo', () => {
    expect(todo("buy milk".toBe("buy milk")))
})

But the test failed.