Optional java

package me.helioalbano.purejava;

import static org.junit.jupiter.api.Assertions.*;

import java.util.NoSuchElementException;
import java.util.Optional;

import org.junit.jupiter.api.Test;

class OptionalTest {

  @Test
  void whenOptionalReturnsEmpty() {
    Optional<User> emptyUser = Optional.empty();

    assertThrows(NoSuchElementException.class, () -> {
      emptyUser.get();
    });
  }

  @Test
  void whenOptionReturnNullFor_Of() {
    Optional<User> nullUser = Optional.of(null);

    assertThrows(NullPointerException.class, () -> {
      nullUser.get();
    });
  }

  @Test
  void returningAObjectUsignOfNullableAsNull() {
    Optional<User> obj = Optional.ofNullable(null);

    assertTrue(obj.isEmpty());
  }

  @Test
  void returningAObjectUsingOfNullableWithAValidObject() {
    User john = new User("John Doe");

    Optional<User> user = Optional.ofNullable(john);

    assertTrue(user.isPresent());
    assertEquals("John Doe", user.get().getName());
  }

  @Test
  void usingLambda_ifPresent() {
    User john = new User("John Doe");

    Optional<User> user = Optional.ofNullable(john);

    user.ifPresent(u -> assertEquals("John Doe", u.getName()));
  }

  @Test
  void returningADefaultValue() {
    User nullUser = null;
    User john = new User("John Doe");

    User user = Optional.ofNullable(nullUser).orElse(john);

    assertEquals("John Doe", user.getName());
  }

  @Test
  void whenOriginalExistsReturnIt() {
    User helio = new User("Helio");
    User john = new User("John Doe");

    User user = Optional.ofNullable(helio).orElse(john);

    assertEquals("Helio", user.getName());
  }
}

class User {
  private String name;

  public User(String name) {
    this.name = name;
  }

  public String getName() {
    return this.name;
  }
}