java-design-patterns/callback/src/test/java/com/iluwatar/callback/CallbackTest.java

/*
 * The MIT License
 * Copyright © 2014-2021 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package com.iluwatar.callback;

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

import org.junit.jupiter.api.Test;

/**
 * Add a field as a counter. Every time the callback method is called increment this field. Unit
 * test checks that the field is being incremented.
 * <p>
 * Could be done with mock objects as well where the call method call is verified.
 */
public class CallbackTest {

  private Integer callingCount = 0;

  @Test
  public void test() {
    Callback callback = () -> callingCount++;

    var task = new SimpleTask();

    assertEquals(Integer.valueOf(0), callingCount, "Initial calling count of 0");

    task.executeWith(callback);

    assertEquals(Integer.valueOf(1), callingCount, "Callback called once");

    task.executeWith(callback);

    assertEquals(Integer.valueOf(2), callingCount, "Callback called twice");

  }
}