Java Assert.assertEquals案例详解

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if情况都不命中, 那么表明1参和2参实际是不相等, 所以代码会往下执行failNotEquals(String message, Object expected, Object actual)方法，并在此方法中抛出异常, 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);}

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