如何使用 Hamcrest assertThat() 匹配器在 Java 中创建 JUnit 测试用例 – 完整教程

已发表: 2022-02-05

如何使用Hamcrest for testing ？前一段时间，我写了一篇包含所有细节的 Hello World JUnit 文章。在本教程中，我们将详细介绍how to use Hamcrest to create JUnit 。

Hamcrest 是一个 Java testing framework ，匹配器与 JUnit 框架捆绑在一起，以创建更具可读性的 Java 单元测试。我今天试过了，我非常喜欢它。

非常简单和完整的文档使其完美。

如果您有以下任何问题，那么您来对地方了：

使用 Eclipse 在 Java 中编写 JUnit 测试用例
如何用Java编写junit测试用例
Java 中的示例 JUnit 测试用例
使用Hamcrest Matchers编写 JUnit 测试用例
JUnit 测试中assertThat vs Assert方法的优势
hamcrest assertthat()教程
使用 Hamcrest 进行测试

让我们开始吧：

在 Eclipse 中创建 Java 类CrunchifyHemcrestJUnitTest.java 。我们将创建 4 种不同类别的测试。

为Java List创建 JUnit 测试用例
为 Java Map 创建 JUnit 测试用例
为 Java 对象创建 JUnit 测试用例
为空检查创建 JUnit 测试用例

以下是顶级 Hamcrest 匹配器：

是（）
有项目（）
有大小（）
包含（）
包含InAnyOrder()

下面的教程涵盖了几乎所有将一直通过的匹配器测试用例。只需修改以创建误报等。

您需要在项目中添加以下 maven 依赖项。

< dependency >

< groupId > org . hamcrest < / groupId >

< artifactId > hamcrest - all < / artifactId >

< version > 1.3 < / version >

< / dependency >

只需将其添加到pom.xml文件中。如果您没有看到 pom.xml，请按照本教程进行操作。

这是一个完整的Java代码

只需右键单击一个类并Run As -> JUnit Test 。

CrunchifyHamcrestJUnitTest.java

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package crunchify . com . java . tutorials ;

import org . hamcrest . collection . IsEmptyCollection ;

import org . hamcrest . collection . IsMapContaining ;

import org . hamcrest . core . IsNull ;

import org . junit . Test ;

import java . util . * ;

import static org . hamcrest . CoreMatchers . * ;

import static org . hamcrest . MatcherAssert . assertThat ;

import static org . hamcrest . Matchers . hasProperty ;

import static org . hamcrest . collection . IsCollectionWithSize . hasSize ;

import static org . hamcrest . collection . IsIterableContainingInAnyOrder . containsInAnyOrder ;

import static org . hamcrest . collection . IsIterableContainingInOrder . contains ;

/**

* @author Crunchify.com

* <p>

* Hamcrest JUnit Tutorials by Crunchify.com

* 1. Create JUnit testcases for Java List

* 2. Create JUnit testcases for Java Map

* 3. Create JUnit testcases for Java Object

* 4. Create JUnit testcases for Null Check

public class CrunchifyHamcrestJUnitTest {

// Testcase-1: JUnit for List

@Test

public void crunchifyListJUnitTests ( ) {

// List: An ordered collection (also known as a sequence). The user of this interface has precise control over where in the list each element is inserted.

// The user can access elements by their integer index (position in the list), and search for elements in the list.

List <String> company = Arrays . asList ( "Crunchify.com" , "Google.com" , "Facebook.com" ) ;

// asList(): Returns a fixed-size list backed by the specified array. Changes made to the array will be visible in the returned list,

// and changes made to the list will be visible in the array.

// The returned list is Serializable and implements RandomAccess.

List <String> crunchifyCompany = Arrays . asList ( "Crunchify.com" , "Google.com" , "Facebook.com" ) ;

crunchifyLog ( "\n~~~~~~~~~~~JUnit List Check Test~~~~~~~~~~~" ) ;

crunchifyLog ( "1) assertThat(company, is(crunchifyCompany)) check" ) ;

// A shortcut to the frequently used is(equalTo(x)).

assertThat ( company , is ( crunchifyCompany ) ) ;

crunchifyLog ( "2) .hasItems() check" ) ;

assertThat ( company , hasItems ( "Crunchify.com" ) ) ;

crunchifyLog ( "3) .hasSize() check" ) ;

assertThat ( company , hasSize ( 3 ) ) ;

assertThat ( company . size ( ) , is ( 3 ) ) ;

crunchifyLog ( "4) .contains() and .containsInAnyOrder() check" ) ;

assertThat ( company , contains ( "Crunchify.com" , "Google.com" , "Facebook.com" ) ) ;

assertThat ( company , containsInAnyOrder ( "Google.com" , "Crunchify.com" , "Facebook.com" ) ) ;

// FAIL

// assertThat(company, contains("Google.com", "Crunchify.com", "Facebook.com"));

crunchifyLog ( "5) .empty() check" ) ;

assertThat ( company , not ( IsEmptyCollection . empty ( ) ) ) ;

assertThat ( new ArrayList < > ( ) , IsEmptyCollection . empty ( ) ) ;

}

private void crunchifyLog ( String crunchifyText ) {

System . out . println ( crunchifyText ) ;

}

@Test

public void crunchifyMapJUnitTests ( ) {

Map < String , String > company = new HashMap < > ( ) ;

company . put ( "C" , "Crunchify.com" ) ;

company . put ( "G" , "Google.com" ) ;

company . put ( "F" , "Facebook.com" ) ;

// Map: An object that maps keys to values. A map cannot contain duplicate keys; each key can map to at most one value.

// This interface takes the place of the Dictionary class, which was a totally abstract class rather than an interface.

Map < String , String > crunchifyCompany = new HashMap < > ( ) ;

crunchifyCompany . put ( "C" , "Crunchify.com" ) ;

// put(): Associates the specified value with the specified key in this map (optional operation).

// If the map previously contained a mapping for the key, the old value is replaced by the specified value.

// (A map m is said to contain a mapping for a key k if and only if m.containsKey(k) would return true.)

crunchifyCompany . put ( "G" , "Google.com" ) ;

crunchifyCompany . put ( "F" , "Facebook.com" ) ;

crunchifyLog ( "\n~~~~~~~~~~~ JUnit Map Check Test - All tests will PASS in our example ~~~~~~~~~~~" ) ;

crunchifyLog ( "1) assertThat(company, is(crunchifyCompany) check" ) ;

assertThat ( company , is ( crunchifyCompany ) ) ;

crunchifyLog ( "2) assertThat(company.size(), is(3)) check" ) ;

assertThat ( company . size ( ) , is ( 3 ) ) ;

crunchifyLog ( "3) .hasEntry() check which creates a matcher for Maps matching at least one entry whose key equals the specified key & value." ) ;

assertThat ( company , IsMapContaining . hasEntry ( "C" , "Crunchify.com" ) ) ;

assertThat ( company , not ( IsMapContaining . hasEntry ( "G" , "Twitter.com" ) ) ) ;

crunchifyLog ( "4) .hasKey() creates a matcher for Maps matching at least one key that is equal to the specified key." ) ;

assertThat ( company , IsMapContaining . hasKey ( "F" ) ) ;

crunchifyLog ( "5) .hasValue() creates a matcher for Maps matching at least one key that is equal to the specified value." ) ;

assertThat ( company , IsMapContaining . hasValue ( "Crunchify.com" ) ) ;

}

@SuppressWarnings ( "unchecked" )

@Test

public void crunchifyObjectJUnitTests ( ) {

List <Company> list = Arrays . asList ( new Company ( "Crunchify" , 10 ) , new Company ( "Google" , 30000 ) ) ;

assertThat ( list , hasItems ( new Company ( "Crunchify" , 10 ) , new Company ( "Google" , 30000 ) ) ) ;

assertThat ( list , containsInAnyOrder ( new Company ( "Google" , 30000 ) , new Company ( "Crunchify" , 10 ) ) ) ;

assertThat ( list , containsInAnyOrder ( hasProperty ( "name" , is ( "Google" ) ) , hasProperty ( "name" , is ( "Crunchify" ) ) ) ) ;

crunchifyLog ( "\n~~~~~~~~~~~ JUnit Object Check Test Completed ~~~~~~~~~~~" ) ;

}

// Create Company Object

public static class Company {

public Company ( String name , int employeeCount ) {

this . name = name ;

this . employeeCount = employeeCount ;

}

private String name ;

private int employeeCount ;

public int getEmployeeCount ( ) {

return employeeCount ;

}

public void setEmployeeCount ( int employeeCount ) {

this . employeeCount = employeeCount ;

}

public String getName ( ) {

return name ;

}

public void setName ( String name ) {

this . name = name ;

}

// Test equal, override equals() and hashCode()

@Override

public boolean equals ( Object c ) {

if ( this == c )

return true ;

if ( c == null | | getClass ( ) ! = c . getClass ( ) )

return false ;

Company fruit = ( Company ) c ;

return employeeCount == fruit . employeeCount && Objects.equals(name, fruit.name);

}

@Override

public int hashCode ( ) {

return Objects . hash ( name , employeeCount ) ;

}

@Test

public void crunchifyNullCheckJUnitTest ( ) {

// Two ways to check isNull

assertThat ( null , is ( nullValue ( ) ) ) ;

assertThat ( null , is ( IsNull . nullValue ( ) ) ) ;

// Two ways to check isNotNull

assertThat ( "crunchify" , is ( notNullValue ( ) ) ) ;

assertThat ( "crunchify" , is ( IsNull . notNullValue ( ) ) ) ;

crunchifyLog ( "\n~~~~~~~~~~~ JUnit Null Check Test Completed ~~~~~~~~~~~" ) ;

}

Eclipse 控制台输出：

只需将上面的程序作为 Java 应用程序运行，您应该会看到如下所示的结果。

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ JUnit Object Check Test Completed ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ JUnit Null Check Test Completed ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ JUnit List Check Test ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

1 ) assertThat ( company , is ( crunchifyCompany ) ) check

2 ) . hasItems ( ) check

3 ) . hasSize ( ) check

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ JUnit List Check Test ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

1 ) assertThat ( company , is ( crunchifyCompany ) ) check

2 ) . hasItems ( ) check

3 ) . hasSize ( ) check

4 ) . contains ( ) and . containsInAnyOrder ( ) check

5 ) . empty ( ) check

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ JUnit Map Check Test - All tests will PASS in our example ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

1 ) assertThat ( company , is ( crunchifyCompany ) check

2 ) assertThat ( company . size ( ) , is ( 3 ) ) check

3 ) . hasEntry ( ) check which creates a matcher for Maps matching at least one entry whose key equals the specified key & value .

4 ) . hasKey ( ) creates a matcher for Maps matching at least one key that is equal to the specified key .

5 ) . hasValue ( ) creates a matcher for Maps matching at least one key that is equal to the specified value .

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ JUnit Object Check Test Completed ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ JUnit Null Check Test Completed ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Process finished with exit code 0

如果您在运行上述程序时遇到任何问题，请告诉我们。