测试 toString Java 代码时出错

Question

我正在尝试为 "Book" class 编写一些测试代码，从其他 classes 获取和设置图书信息：ISBN（字符串）、标题（字符串）、作者 (String)、发布日期 (SimpleDateFormat "MMM.dd.yyy")、价格 (Double) 和摘要内容 (Blob)。当我尝试运行对全部或部分代码（我有改了无数次应该设置的format和String):

@Test
public void testToString() {
    Book testBook6 = new Book();
    Title testTitle6 = new Title("Title: Moby Dick, ");
    Author testAuthor6 = new Author("Author: Mark Twain, ");
    ISBN testISBN6 = new ISBN("ISBN: 000-00-000-0000-0");
    testBook6.setTitle(testTitle6);
    testBook6.setAuthor(testAuthor6);
    testBook6.setISBN(testISBN6);
    assertEquals("Title: Moby Dick, Author: Mark Twain, ISBN: 000-00-000-0000-0", testBook6.toString());        
}

我收到一个错误：

org.junit.ComparisonFailure: expected:<[Title: Moby Dick, Author: Mark Twain, ISBN: 000-00-000-0000-0]> but was:<[book.application.Book@48533e64]>
    at org.junit.Assert.assertEquals(Assert.java:115)
    at org.junit.Assert.assertEquals(Assert.java:144)
    at book.application.BookTest.testToString(BookTest.java:61)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access[=12=]0(ParentRunner.java:58)
    at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

当我尝试运行我的剪贴簿中的代码时：

Book testBook = new Book();
ISBN testISBN = new ISBN("ISBN: 000-00-000-0000-0");
Title testTitle = new Title("Title: Moby Dick, ");
Author testAuthor = new Author("Author: Mark Twain, ");
Date dNow = new Date( );
SimpleDateFormat ft = new SimpleDateFormat ("MMMM.dd.yyyy");
Price testPrice = new Price(2.25);
Blob testBlob = new Blob("Blah, Blah, Blah");

testBook.setISBN(testISBN);
testBook.setTitle(testTitle);
testBook.setAuthor(testAuthor);
testBook.setPrice(testPrice);
testBook.setBlob(testBlob);

System.out.println(testBook.toString());

为了看看发生了什么，我只能得到 "book.application.Book@1794d431" 的 return，每次我运行时数字（例如 1794d431）都会随机变化。 "Book" 从中获取和设置的每个 class 的所有测试都通过了，并且没有标记错误。这只是我的第二个 Java 项目，所以我对此很陌生；但是，我似乎遇到了困难，当然需要一些帮助！

提前致谢！

package book.application;

import java.time.LocalDate;

public class Book {

    //fields
    private ISBN ISBN;
    private Title Title;
    private Author Author;
    private LocalDate publishDate;
    private Price Price;
    private Blob Blob;




    //getters and setters
    public LocalDate getPublishDate() {
        return publishDate;
    }
    public void setPublishDate(LocalDate publishDate) {
        this.publishDate = publishDate;
    }
    public ISBN getISBN() {
        return ISBN;
    }
    public void setISBN(ISBN ISBN) {
        this.ISBN = ISBN;
    }
    public Title getTitle() {
        return Title;
    }
    public void setTitle(Title Title) {
        this.Title = Title;
    }
    public Author getAuthor() {
        return Author;
    }
    public void setAuthor(Author Author) {
        this.Author = Author;
    }
    public Price getPrice() {
        return Price;
    }
    public void setPrice(Price Price) {
        this.Price = Price;
    }
    public Blob getBlob() {
        return Blob;
    }
    public void setBlob(Blob Blob) {
        this.Blob = Blob;
    }   

    @Override
    public String toString() {
        return "Title: " + this.getTitle().getTitle() + ", Author: " + this.getAuthor().getAuthor() + ", ISBN: " + this.getISBN().getISBN() + ", Published on: " + LocalDate.now() + ", costing: $" + this.getPrice().getPrice();
    }

}

Answer 1

该错误表示您忘记覆盖正在测试的 class 的 toString 方法。

转到您的 Book class，并添加 toString:

的实现

public class Book {
    ... // things you already have
    // Add an implementation:
    @Override
    public String toString() {
        // Add code constructing the output to satisfy your unit test
    }
}

Answer 2

您需要重写 Book 上的 toString 方法 class。目前它使用默认的 toString() 功能，其中 returns 对象类型和哈希码。

您的方法可能如下所示：

@Override
public String toString() { 
    return "Title: '" + this.title + "', Author: '" + this.author + "', ISBN: '" + this.isbn + "'";
}

如果您不清楚这意味着什么，check out the API for the Object class。在 Java 中，所有 class 都扩展了 Object，因此您可以访问和覆盖（替换）此 class 中的许多方法。 ToString 就是这样一种方法，该方法的默认行为不是您所期望的，因此在 Java 中创建新的 class 时覆盖 toString() 是很常见的。您可能想要查看的另一种方法是 equals().

Answer 3

您的 toString() 方法似乎未实现并且具有默认的 Object 版本。如果您 post 您的 Book 代码，我们可以进一步帮助您。

此外，为了比较字符串，通常最好做 AssertTrue(string1.Equals(string2))

测试 toString Java 代码时出错

Errors testing toString Java code

java

testing

tostring