堆棧內存溢出
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由於 nullpointerexception，無法通過 junit 測試

[英]Cannot pass junit test because of the nullpointerexception

 原文  2021-11-24 15:47:20  9   1    java/ junit/ nullpointerexception

問題描述

由於 NullPointerException，我的 junit 測試給出了以下失敗，但我必須將空間分配為 null，我該如何解決這個問題？ 我添加錯誤的圖片在此處輸入圖片描述

public class Guest {

    private Guest guest=null;
    private String customerName;
    private Room room= null; // This is line 7
    
    /**
     * @param name of the new Customer 
     * **/
    public Guest(String customerName){
    this.customerName=customerName;
    }
    
    
    /**
     * @param checkinRoom the room to be assigned to this guest
     * @return returns true if runs successfully 
     * **/
    public boolean checkin(Room checkinRoom) {
    boolean result=false;
    if( this.room==null && room.getGuest()==null) {
        this.room=checkinRoom;
        checkinRoom.setGuest(this);
        result=true;
    }
    return result;
    
    }
    
    /**
     * Checks out the customer out of the room
     * @return returns true if runs successfully
     * **/
    public boolean checkout() {
        if(this.getRoom()==null) {
            return false;
        }else {
            this.getRoom().setGuest(null);
            this.room=null;
            return true;
            
            
        }
    
    }
    /**
     * @return the room of the customer if exists or null
     * 
     * **/
    
    public Room getRoom() {
        return this.room;
    }
/**
 * @return returns name of the customer;
 * 
 * **/
    public String getName(){
        return this.customerName;
        
    }
    public String toString() {
        return "Guest " + this.getName();
        
    }

my junit fails are: java.lang.NullPointerException: Cannot invoke "java.lang.Integer.intValue()" because "null" is null

以下是分配給客戶的房間代碼

package ss.week2.hotel;

public class Room {
    private int number;
    private Guest guest;
    private Room room;
    
    
    /**
    * Creates a <code>Room</code> with the given number, without a guest.
    * @param no number of the new <code>Room</code>
    */
    public Room(int number) {
        this.number = number;
    }

    /**
     * Returns the number of this Room
     */
    public int getNumber() {
        return number;
    }

    /**
     * Returns the current guest living in this Room
     * @return the guest of this Room, null if not rented
     */
    public Guest getGuest() {
        return guest;
    }
    
    
    /**
     * Assigns a Guest to this Room.
     * @param guest the new guest renting this Room, if null is given, Room is empty afterwards
     */
    public void setGuest(Guest guest) {
        this.guest = guest;
    }
    
    public String toString() {
            return "Room "+ this.getNumber();
    }
}

我添加了完整的 junit 測試

package ss.week2.test;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import ss.week2.hotel.Guest;
import ss.week2.hotel.Room;

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

/**
 * Test program for Room and Guest.
 * Lab Exercise Software Systems
 * @author Arend Rensink, Jip Spel
 */
public class GuestTest {
    /** Test variable for a <tt>Guest</tt>-object. */
    private Guest ot;
    /** Test variable for a <tt>Guest</tt>-object. */
    private Guest sien;
    /** Test variable for a <tt>Room</tt>-object. */
    private Room k101;
    /** Test variable for a <tt>Room</tt>-object. */
    private Room k102;

    /**
     * Sets initial variables to a well-defined initial value.
     * <p>
     * Assigns a <tt>Guest</tt> object to the <tt>ot</tt> instance variable with the
     * name {@code "Ot"} and assigns a <tt>Guest</tt> object to the <tt>sien</tt>
     * instance variable with the name {@code "Sien"}. Also assigns <tt>Room</tt>
     * objects to instance variables <tt>k101</tt> and <tt>k102</tt> with numbers
     * <tt>101</tt> and <tt>102</tt> respectively. Lastly, checks in <tt>sien</tt>
     * in room <tt>k102</tt>.
     */
    @BeforeEach
    public void setUp() {
        // initialisation of Guest-variables
        ot = new Guest("Ot");
        sien = new Guest("Sien");
        // initialisation of Room-variables
        k101 = new Room(101);
        k102 = new Room(102);
        // check in sien to room 102
        sien.checkin(k102);
    }

    /**
     * Tests if the initial condition complies to the specification.
     */
    @Test
    public void testInitialcondition() {
        assertEquals("Ot", ot.getName());
        assertEquals("Sien", sien.getName());
        assertNull(ot.getRoom());
        assertEquals(k102, sien.getRoom());
    }

    /**
     * Tests checking in a new guest in an empty room.
     * Calls <tt>ot.checkin(k101)</tt>.
     */
    @Test
    public void testCheckinEmpty() {
        assertTrue(ot.checkin(k101));
        assertEquals(k101, ot.getRoom());
        assertEquals(ot, k101.getGuest());
    }

    /**
     * Checks checking in a new guest in a room that is already taken.
     * Calls <tt>ot.checkin(k102)</tt>.
     */
    @Test
    public void testCheckinTaken() {
        assertFalse(ot.checkin(k102));
        assertNull(ot.getRoom());
        assertEquals(sien, k102.getGuest());
    }

    /**
     * Tests checking out a guest that rented a room.
     * Calls <tt>sien.checkout()</tt>.
     */
    @Test
    public void testCheckoutKnown() {
        assertTrue(sien.checkout());
        assertNull(sien.getRoom());
        assertNull(k102.getGuest());
    }

    /**
     * Tests checking out a guest that didn't rent a room.
     * Calls <tt>ot.checkout()</tt>.
     */
    @Test
    public void testCheckoutUnknown() {
        assertNull(ot.getRoom());
        assertFalse(ot.checkout());
        assertNull(ot.getRoom());
    }
}

堆棧跟蹤：

java.lang.NullPointerException: Cannot invoke "java.lang.Integer.intValue()" because "null" is null
    at ss.week2.hotel.Guest.<init>(Guest.java:7)
    at ss.week2.test.GuestTest.setUp(GuestTest.java:39)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
    at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
    at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptLifecycleMethod(TimeoutExtension.java:126)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptBeforeEachMethod(TimeoutExtension.java:76)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeMethodInExtensionContext(ClassBasedTestDescriptor.java:490)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$synthesizeBeforeEachMethodAdapter$19(ClassBasedTestDescriptor.java:475)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeBeforeEachMethods$2(TestMethodTestDescriptor.java:167)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeBeforeMethodsOrCallbacksUntilExceptionOccurs$5(TestMethodTestDescriptor.java:195)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeBeforeMethodsOrCallbacksUntilExceptionOccurs(TestMethodTestDescriptor.java:195)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeBeforeEachMethods(TestMethodTestDescriptor.java:164)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:127)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:84)
    at org.eclipse.jdt.internal.junit5.runner.JUnit5TestReference.run(JUnit5TestReference.java:98)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:40)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:529)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:756)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:452)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:210)

1 個解決方案

解決方案1
 0  2021-11-25 20:53:48

您發布的代碼與導致您失敗的代碼不同。

導致您失敗的代碼看起來如何以及為什么會這樣，我不知道。

當我運行您的代碼時，對於五種測試方法中的每一種，我都會遇到以下異常：

java.lang.NullPointerException
    at ss.week2.hotel.Guest.checkin(Guest.java:22)
    at ss.week2.test.GuestTest.setUp(GuestTest.java:48)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at …

我可以告訴你為什么。 正如您從堆棧跟蹤中看到的那樣，異常是通過設置發生的，因此對於所有測試方法都是一樣的。 由於設置失敗，該方法本身無法執行。 問題出在Guest.checkin()這一行的邏輯中：

    if (this.room == null && room.getGuest() == null) {

當您在setUp()中嘗試檢查 sien 時，他們的房間是 null。 所以上述條件的第一部分為真，Java 嘗試評估第二部分。 由於room是 null， room.getGuest()拋出NullPointerException 。

您可能打算：

    if (room == null && checkinRoom.getGuest() == null) {

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