1.背景

在设计自动化 cases 时，遵守的核心原则是 3A（Arrange-> Actor ->Assert）原则;

断言工具是否强大直接影响到用例的执行效率，本文将介绍一种流式断言神器：AssertJ。

在 JAVA cases 中常用的断言工具有 JUnit 自带的 Assert，还有 hamcrest 的 assertThat(之前总结过http://blog.csdn.net/neven7/article/details/42489723)，这些工具对于 AssertJ 来说都相形见绌。

2.AssertJ 介绍

AseertJ: JAVA 流式断言器，什么是流式，常见的断言器一条断言语句只能对实际值断言一个校验点，而流式断言器，支持一条断言语句对实际值同时断言多个校验点。

AssertJ 支持如下模块：

Core：AssertJ core is a Java library that provides a fluent interface for writing assertions. 

Assertions generator：Use the Assertion Generator to create assertions specific to your own classes.

Guava：AssertJ assertions for Guava provides assertions for Guava types like Multimap, Table, Optional, Range or ByteSource.

Joda-Time：AssertJ assertions for Joda-Time provides assertions for Joda-Time types like DateTime and LocalDateTime.

DB：AssertJ-DB provides assertions to test data in a database.

Neo4j：Provides assertions for Neo4j 2 or higher.

Swing：AssertJ Swing is a Java library that provides a fluent interface for functional Swing UI testing.

3.AssertJ 使用

本文将主要介绍 Core 下常用的断言方法。

版本要求：

AssertJ major versions depend on different Java versions :

AssertJ 1.x requires Java 6 or higher (suitable for Android)
AssertJ 2.x requires Java 7 or higher (should be suitable for Android - please file an issue if it's not the case)
AssertJ 3.x requires Java 8 or higher (not suitable for Android due to Path assertions)

本文使用 JDK7, maven pom.xml 添加依赖：

<dependency>
            <groupId>org.assertj</groupId>
            <artifactId>assertj-core</artifactId>
            <!-- use 2.4.1 for Java 7 projects -->
            <version>2.4.1</version>
            <!-- <version>3.4.1</version> -->
            <scope>test</scope>
</dependency>

在 cases 中 import assertj

import static org.assertj.core.api.Assertions.*;

先介绍一个实例，比较类对象，用到了 isEqualToComparingFieldByFieldRecursively，嵌套比较字段值。

package com.weibo.qa.testcase.lab;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.testng.annotations.Test;

import static org.assertj.core.api.Assertions.*;

/**
 * 
 * 两个类对象比较
 * 
 * @author hugang
 *
 */
class A {
    List<String> list = new ArrayList<String>();
    String str;

}

class B {
    A aB = new A();
    String test;
}
public class AssertJTest {
    @Test
    public void testAssertJ() {

        A a1 = new A();
        A a2 = new A();

        a1.str = "hello";
        a2.str = "hello";

        a1.list.add("world");
        a2.list.add("world");

        B b1 = new B();
        B b2 = new B();


        b1.test = "b1";
        b2.test = "b1";

        b1.aB.list = a1.list;
        b1.aB.str = a1.str;

        b2.aB.list = a2.list;
        b2.aB.str = a2.str;


        // 不包含 对象类型
        assertThat(a1).isEqualToComparingFieldByField(a2);

        // 对象类型 只比较引用
        // assertThat(b1).isEqualToComparingFieldByField(b2);


        // 含有嵌式比较，含有对象类型的字段，再比较对象内的数据
        assertThat(b1).isEqualToComparingFieldByFieldRecursively(b2);

    }
}

常用的一些用法：

添加错误提示信息： as

assertThat("abc").as("校验abc").isEqualTo("abcd");

错误提示：
org.junit.ComparisonFailure: [校验abc] expected:<"abc[d]"> but was:<"abc[]">

链式校验.

// isEqualTo 相等， contains包含
assertThat("abc").as("校验abc").isEqualTo("abc").contains("d");

错误提示：
FAILED: testAssertJ
java.lang.AssertionError: [校验abc] 
Expecting:
 <"abc">
to contain:
 <"d"> 

null 判断

Object object = null;
assertThat(object).isNotNull();

AILED: testAssertJ
java.lang.AssertionError: 
Expecting actual not to be null


Object object = null;
assertThat(object).isNull();

是否在某个范围内

List list = new ArrayList();
assertThat(list).isIn(new ArrayList(), new HashMap());



assertThat(list).isNotIn(new ArrayList(), new HashMap());
java.lang.AssertionError: 
Expecting:
 <[]>
not to be in:
 <[[], {}]>

大小

List list = new ArrayList();

assertThat(list).hasSize(1);
FAILED: testAssertJ
java.lang.AssertionError: 
Expected size:<1> but was:<0> in:
<[]>

等等，实在太多了，等你来发掘。

可参见官方 wiki: http://joel-costigliola.github.io/assertj/index.html