Learning tutorial on void method in Java programming

void keyword
This section explains how to declare and call a void method.
The following example declares a method named printGrade and calls it to print the given score.
Example

public class TestVoidMethod {
 
  public static void main(String[] args) {
   printGrade(78.5);
  }
 
  public static void printGrade(double score) {
   if (score >= 90.0) {
     System.out.println('A');
   }
   else if (score >= 80.0) {
     System.out.println('B');
   }
   else if (score >= 70.0) {
     System.out.println('C');
   }
   else if (score >= 60.0) {
     System.out.println('D');
   }
   else {
     System.out.println('F');
   }
  }
}

The compilation and running results of the above example are as follows:

C

The printGrade method here is a void type method, which does not return a value .
The call to a void method must be a statement. Therefore, it is called as a statement on the third line of the main method. Just like any statement that ends with a semicolon.

Single test void type method
The Service layer of Java will have many void type methods, such as save* and update*. These methods only do some updates and will not return a value. Tests cannot be written based on the return value of the method, and can only use special methods;

Environment of this method: Mockito, testng

Method to be tested:

Want to be tested VOID method

@Override
  public void updateRuleName(Long ruleId, String newRuleName, Long ucId) {
    Assert.notNull(ruleId, "规则ID不能为Null");
    Assert.notNull(newRuleName, "规则名称不能为Null");
    Assert.notNull(ucId, "操作人的UCID不能为Null");
     
    String cleanNewRuleName = StringUtils.trim(newRuleName);
    if (StringUtils.isBlank(cleanNewRuleName)) {
      throw new IllegalArgumentException("新的规则名称不能为空");
    }
     
    // 查询规则对象
    Rule rule = queryRuleById(ruleId);
    if (null == rule) {
      throw new IllegalDataException("没有查到该规则");
    }
     
    rule.setRuleId(ruleId);
    rule.setRuleName(cleanNewRuleName);
    rule.setUpdateUcid(ucId);
    rule.setUpdateTime(new Date());
     
    ruleDao.updateSelective(rule);
  }

Tested method:

void returned method tested

@Test
  public void testUpdateRuleName() {
    Long ruleId = 1L;
    String newRuleName = "newRuleName";
    Long ucId = 123L;
     
    List<Rule> rules = new ArrayList<Rule>();
    Rule rule = new Rule();
    rule.setRuleStatus((byte) DBValueSetting.RULE_STATUS_TAKE_EFFECT);
    rules.add(rule);
     
    // 查询规则对象
    Map<String, Object> params = new HashMap<String, Object>();
    params.put("ruleId", ruleId);
    Mockito.when(ruleDao.queryRulesByCondition(params)).thenReturn(rules);
     
    Mockito.doAnswer(new Answer<Object>() {
      public Object answer(InvocationOnMock invocation) {
        // 断点2：这里随后执行
        Rule rule = (Rule) invocation.getArguments()[0];
        Assert.assertTrue(rule.getRuleName().equals("newRuleName"));
        return null;
      }
    }).when(ruleDao).updateSelective(Mockito.any(Rule.class));
     
    // 断点1：先执行到这里
    ruleService.updateRuleName(ruleId, newRuleName, ucId);
  }

As shown in the comments, if If two breakpoints are added, during the execution process, the last call line will be executed first. During the execution of endpoint 1, the stub of endpoint 2 will be executed. At this time, the input parameters of method execution can be obtained at breakpoint 2. , perform Assert verification on the input parameters to achieve the purpose;

new Anwer is an interface with only one method, which is used to set the proxy execution entrance for method calls

implementation of doAnswer

public interface Answer<T> {
  /**
   * @param invocation the invocation on the mock.
   *
   * @return the value to be returned
   *
   * @throws Throwable the throwable to be thrown
   */
  T answer(InvocationOnMock invocation) throws Throwable;
}

When the code is executed to "ruleDao.updateSelective(rule);", the interceptor called for the mock object will be triggered. In the interceptor, a dynamic proxy will be created. The dynamic proxy The invocation is the method covered in new Answer;

uses interception and proxy methods to realize the setting and acquisition of input parameters and output parameters of the mock object method. Using this method, you can calibrate Check the execution class call inside the VOID method.

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