JUnit 为所有原始类型 和 对象 以及 （原始或对象的）数组提供了重载的断言方法 。参数顺序是期望值，然后是实际值。可选地，第一个参数可以是失败时输出的String消息。
 

有一个稍微不同的断言，assertThat具有可选失败消息的参数，实际值和Matcher对象。请注意，与其他assert方法相比，期望值和实际值是相反的。

让我们创建一个简单的maven项目并演示所有断言方法。

让我们创建一个简单的Maven项目。通过执行以下命令创建简单的Maven项目：

mvn archetype:generate
-DgroupId=org.yourcompany.project
-DartifactId=application

在maven项目构建成功后，maven将创建默认文件夹结构。

Test

── pom.xml
└── src
    ├── main
    │   ├── java
    │   │   └── com
    │   │       └── yiidian
    │   │           └── junit
    │   ├── resources
    └── test
        ├── java
        │   └── com
        │       └── yiidian
        │           └── junit
        │               └── AssertTests.java
        └── resources

<dependency>
 <groupId>junit</groupId>
 <artifactId>junit</artifactId>
 <version>4.12</version>
 <scope>test</scope>
</dependency>

4 创建一个AssertTests.java并运行测试

import static org.hamcrest.CoreMatchers.allOf;
import static org.hamcrest.CoreMatchers.anyOf;
import static org.hamcrest.CoreMatchers.both;
import static org.hamcrest.CoreMatchers.containsString;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.everyItem;
import static org.hamcrest.CoreMatchers.hasItems;
import static org.hamcrest.CoreMatchers.not;
import static org.hamcrest.CoreMatchers.sameInstance;
import static org.hamcrest.CoreMatchers.startsWith;
import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNotSame;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertSame;
import static org.junit.Assert.assertThat;
import static org.junit.Assert.assertTrue;

import java.util.Arrays;
/**
 * 一点教程网： http://www.yiidian.com
 */
import org.hamcrest.core.CombinableMatcher;
import org.junit.Test;

public class AssertTests {
  @Test
  public void testAssertArrayEquals() {
    byte[] expected = "trial".getBytes();
    byte[] actual = "trial".getBytes();
    assertArrayEquals("failure - byte arrays not same", expected, actual);
  }

  @Test
  public void testAssertEquals() {
    assertEquals("failure - strings are not equal", "text", "text");
  }

  @Test
  public void testAssertFalse() {
    assertFalse("failure - should be false", false);
  }

  @Test
  public void testAssertNotNull() {
    assertNotNull("should not be null", new Object());
  }

  @Test
  public void testAssertNotSame() {
    assertNotSame("should not be same Object", new Object(), new Object());
  }

  @Test
  public void testAssertNull() {
    assertNull("should be null", null);
  }

  @Test
  public void testAssertSame() {
    Integer aNumber = Integer.valueOf(768);
    assertSame("should be same", aNumber, aNumber);
  }

  // JUnit Matchers assertThat
  @Test
  public void testAssertThatBothContainsString() {
    assertThat("albumen", both(containsString("a")).and(containsString("b")));
  }

  @Test
  public void testAssertThatHasItems() {
    assertThat(Arrays.asList("one", "two", "three"), hasItems("one", "three"));
  }

  @Test
  public void testAssertThatEveryItemContainsString() {
    assertThat(Arrays.asList(new String[] { "fun", "ban", "net" }), everyItem(containsString("n")));
  }

  // Core Hamcrest Matchers with assertThat
  @Test
  public void testAssertThatHamcrestCoreMatchers() {
    assertThat("good", allOf(equalTo("good"), startsWith("good")));
    assertThat("good", not(allOf(equalTo("bad"), equalTo("good"))));
    assertThat("good", anyOf(equalTo("bad"), equalTo("good")));
    assertThat(7, not(CombinableMatcher.<Integer> either(equalTo(3)).or(equalTo(4))));
    assertThat(new Object(), not(sameInstance(new Object())));
  }

  @Test
  public void testAssertTrue() {
    assertTrue("failure - should be true", true);
  }
}

4.1 运行测试

从命令行使用maven运行测试

mvn -Dtest=AssertTests test

[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building junit-assertions-examples 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ junit-assertions-examples ---
[WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ junit-assertions-examples ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ junit-assertions-examples ---
[WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ junit-assertions-examples ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ junit-assertions-examples ---
[INFO] Surefire report directory: E:\Git_Work\junit-developers-guide\junit-assertions-examples\target\surefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.developersguide.junit.assetions.AssertTests
Tests run: 12, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.084 sec

Results :

Tests run: 12, Failures: 0, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.641 s
[INFO] Finished at: 2018-06-27T22:12:19+05:30
[INFO] Final Memory: 6M/19M
[INFO] ------------------------------------------------------------------------

在本指南中，我们通过创建一个简单的maven项目了解了JUnit 4 Framework提供的所有断言。您可以创建更多的测试方法，并应用这些断言以获得实践经验。