Junit4 Assert assertNull()方法

JUnit AssertassertNull(Object object) 当我们想测试一个对象是否为空时，我们可以使用assertNull断言。

1 语法

void org.junit.Assert.assertNull(Object object)

2 参数

object ：对象来检查或空

3 返回值

此方法不返回任何值。

4 示例 

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */

import org.junit.Test;

import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNull;

/**
 * Junit4 Assert assertNull()方法
 */
public class AssertNullExample {
 /**
  * Concatenate the given {@code String} arrays into one,
  * with overlapping array elements included twice.
  * <p>The order of elements in the original arrays is preserved.
  * @param array1 the first array (can be {@code null})
  * @param array2 the second array (can be {@code null})
  * @return the new array ({@code null} if both given arrays were {@code null})
  */
 
 public static String[] concatenateStringArrays( final String[] array1,  final String[] array2) {
     if (array1 == null || array1.length == 0) {
          return array2;
     }
     if (array2 == null || array2.length == 0) {
          return array1;
     }

     final String[] newArr = new String[array1.length + array2.length];
     System.arraycopy(array1, 0, newArr, 0, array1.length);
     System.arraycopy(array2, 0, newArr, array1.length, array2.length);
     return newArr;
 }
 
 @Test
 public void testConcatenateStringArrays() {
     final String[] input1 = new String[] {"myString2"};
     final String[] input2 = new String[] {"myString1", "myString2"};
     final String[] result = concatenateStringArrays(input1, input2);
  
     assertNull(concatenateStringArrays(null, null));
  
     assertEquals(3, result.length);
     assertEquals("myString2", result[0]);
     assertEquals("myString1", result[1]);
     assertEquals("myString2", result[2]);

     assertArrayEquals(input1, concatenateStringArrays(input1, null));
     assertArrayEquals(input2, concatenateStringArrays(null, input2));  
   }
}

输出结果为：