Assert.assertEquals作用

野性酷女 2021-12-10 15:57 311阅读 0赞

junit.framework包下的Assert提供了多个断言方法. 主用于比较测试传递进去的两个参数.

Assert.assertEquals();及其重载方法: 1. 如果两者一致, 程序继续往下运行. 2. 如果两者不一致, 中断测试方法, 抛出异常信息 AssertionFailedError .  
查看源码, 以Assert.assertEquals(int expected, int actual)为例:  
/\*\*  
 \* Asserts that two ints are equal. 断言两个int是相等的  
 \*/  
static public void assertEquals(int expected, int actual) \{  
    assertEquals(null, expected, actual);  
\}

可以看到里面调用了assertEquals(String message, int expected, int actual)方法:

/\*\*  
 \* Asserts that two ints are equal. If they are not  
 \* an AssertionFailedError is thrown with the given message.  
 \* 如果不抛出带有 message 的异常(AssertionFailedError)信息, 则表明两者相等  
 \*/  
static public void assertEquals(String message, int expected, int actual) \{  
    assertEquals(message, Integer.valueOf(expected), Integer.valueOf(actual));  
\}

可以看到, 这里把int类型封箱成为Integer类型. 注释说, 会抛异常, 但这里没有. 没关系, 我们接着看里面调用: assertEquals(String message, Object expected, Object actual)方法:

/\*\*  
 \* Asserts that two objects are equal. If they are not  
 \* an AssertionFailedError is thrown with the given message.  
 \* 如果不抛出带有 message 的异常(AssertionFailedError)信息, 则表明两者相等(这里比较的是Object对象)  
 \*/  
static public void assertEquals(String message, Object expected, Object actual) \{  
    if (expected == null && actual == null) \{  
        return;  
    \}  
    if (expected != null && expected.equals(actual)) \{  
        return;  
    \}  
    failNotEquals(message, expected, actual);  
\}

两个if语句, 判断了两者相等的情况: 引用(地址)相等或者内容相等. 如果这两种情况都不相等, 那么表明1参和2参实际是不相等, 所以基本可以判断出要抛出的异常肯定是在failNotEquals(String message, Object expected, Object actual)方法抛出的, 接下来就比较简单了:

static public void failNotEquals(String message, Object expected, Object actual) \{  
    fail(format(message, expected, actual));  
\}

public static String format(String message, Object expected, Object actual) \{  
    String formatted = "";  
    if (message != null && message.length() > 0) \{  
        formatted = message + " ";  
    \}  
    return formatted + "expected:<" + expected + "> but was:<" + actual + ">";  
\}  
/\*\*  
\* Fails a test with the given message.  
\*/  
static public void fail(String message) \{  
    if (message == null) \{  
        throw new AssertionFailedError();  
    \}  
    throw new AssertionFailedError(message);  
\}

以上可以看出, 最终是由fail(String message)这个方法抛出异常信息!!

Assert.assertEquals()使用方法:  
**使用, 示例代码:**

Assert.assertEquals(true, arry.contains("hello"));  
Assert.assertEquals(39991L, aa.getLong("key3", 0L));  
Assert.assertEquals(true, bb.getBoolean("key4", false));  
Assert.assertEquals(5.3f, cc.getFloat("key5", 0.f));  
Assert.assertEquals(99, dd.getInt("key6", 1));  
Assert.assertEquals("如果打印本信息, 证明参数不相等", 10L, 10);

按照源码分析, 我们可以把一个预期结果作为1参传递进去. 2参传递我们需要测试的方法. 然后执行. 相等, 代码继续往下执行, 不相等, 中断执行, 抛出异常信息!!!

略作一提:  
Assert.assertSame(Object expected, Object actual)方法:  
查看源码, 其比较的是引用地址是否相等, 并没有对内容进行比较:

/\*\*  
 \* Asserts that two objects refer to the same object. If they are not  
 \* the same an AssertionFailedError is thrown.  
 \*/  
static public void assertSame(Object expected, Object actual) \{  
    assertSame(null, expected, actual);  
\}  
/\*\*  
 \* Asserts that two objects refer to the same object. If they are not  
 \* an AssertionFailedError is thrown with the given message.  
 \*/  
static public void assertSame(String message, Object expected, Object actual) \{  
    if (expected == actual) \{  
        return;  
    \}  
    failNotSame(message, expected, actual);  
\}