Java JUNIT 空指针异常
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JUNIT Null Pointer Exception
提问by AnjunaTom
it's my first time using JUNIT and I literally cannot get it to work.
这是我第一次使用 JUNIT，我真的无法让它工作。
I've got a person class, in which has firstName and lastName, and a test class in which I need to test the methods. Everytime I attempt to test one though, if i've wrote a test for the particular method, it fails.
我有一个 person 类，其中有 firstName 和 lastName，还有一个 test 类，我需要在其中测试方法。每次我尝试测试一个方法时，如果我为特定方法编写了一个测试，它就会失败。
Here is my code.
这是我的代码。
Person Class
人物类
public class Person {
private String firstName;
private String lastName;
public Person (String a, String b) {
firstName = a;
lastName = b;
}
public String getfirstName() {
return firstName;
}
public void setfirstName(String firstName) {
this.firstName = firstName;
}
public String getlastName() {
return lastName;
}
public void setlastName(String lastName) {
this.lastName = lastName;
}
@Override
public String toString() {
return firstName + " " + lastName;
}
}
Person Test class
人物测试类
public class PersonTest {
Person p1;
public PersonTest() {
Person p1 = new Person ("Thomas", "Brown");
}
@Before
public void setUp() {}
@After
public void tearDown() {}
@Test
public void testGetfirstName() {
assertEquals("Thomas", p1.getfirstName());
}
@Test
public void testSetfirstName() {}
@Test
public void testGetlastName() {
assertEquals("Brown", p1.getlastName());
}
@Test
public void testSetlastName() {}
@Test
public void testToString() {
assertEquals("Thomas Brown", p1.toString());
}
}
Could anyone point me in the right direction?
有人能指出我正确的方向吗？
采纳答案by Adam Arold
This is the right way to do it:
这是正确的方法：
@Before
public void setUp() {
p1 = new Person ("Thomas", "Brown");
}
You have 2 problems in your code.
您的代码中有 2 个问题。
public PersonTest() {
Person p1 = new Person ("Thomas", "Brown");
}
This creates a local variable and your field p1stays null.
这将创建一个局部变量并且您的字段p1保持为null。
The second is that in your setUpmethod you do not initialize p1.
第二个是在你的setUp方法中你没有 initialize p1。
The method you annotate with @Beforewill run before every test to you should put the initialization there. I also suggest to use more descriptive names so you should change p1to targetor something like that.
您注释的方法@Before将在每次测试之前运行，您应该将初始化放在那里。我还建议使用更具描述性的名称，因此您应该更改p1为target或类似的名称。
Edit:For your set...methods you can do something like this:
编辑：对于您的set...方法，您可以执行以下操作：
public class PersonTest {
private static final String TEST_FIRST_NAME = "some name";
Person target;
// ...
@Test
public void testSetFirstName() {
target.setFirstName(TEST_FIRST_NAME);
Assert.assertEquals(target.getFirstName(), TEST_FIRST_NAME);
}
}
At that point you can assume that getFirstNameworks since you have a test for it as well.
那时你可以假设它getFirstName有效，因为你也有一个测试。
A sidenote:I think you don't have to test getters and setters as long as you generate them with Eclipse. It is just unnesessary.
旁注：我认为只要使用 Eclipse 生成 getter 和 setter，就不必测试它们。这只是不必要的。
回答by Caffe Latte
Change
改变
Person p1 = new Person ("Thomas", "Brown"); //this is local variable
to
到
p1 = new Person ("Thomas", "Brown");// and this will use the instance variable
