如何比较BigDecimals以使我的测试通过？

Question

我有以下同样的奇怪情况进入JUnit测试.

所以我有这个测试方法:

@Test
public void getNavInfoTest() throws ParseException {

    TirAliquotaRamoI expectedObject = new TirAliquotaRamoI();

    DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
    Date date;

    date = formatter.parse("2015-08-01");

    Date dataInizio = formatter.parse("2015-08-01");
    Date dataFine = formatter.parse("2100-12-31");

    expectedObject.setDataElaborazione(date);
    expectedObject.setTassoLordoAnnuoAppl(BigDecimal.ZERO);
    expectedObject.setTassoGiornalieroNetto(BigDecimal.ZERO);
    expectedObject.setAliquota(BigDecimal.ONE);
    expectedObject.setDataInizio(dataInizio);
    expectedObject.setDataFine(dataFine);

    TirAliquotaRamoI tirAliquotaRamoI = pucManager.getNavInfo(date);

    assertEquals(tirAliquotaRamoI.getAliquota(), expectedObject.getAliquota());

}

最后,我只是测试tirAliquotaRamoI.getAliquota()(从数据库查询获得)是否具有为创建的相同字段的相同值expectedObject:

assertEquals(tirAliquotaRamoI.getAliquota(), expectedObject.getAliquota());

因此,使用BigDecimal.ONEconstand 创建预期对象的字段,并使用调试器,我可以看到它的值是1.

而tirAliquotaRamoI.getAliquota()obtaind值1.000000000

因此,从理论上讲,两者都代表相同的值1,但测试失败,我得到:

java.lang.AssertionError: expected:<1.000000000> but was:<1>
    at org.junit.Assert.fail(Assert.java:88)
    at org.junit.Assert.failNotEquals(Assert.java:834)
    at org.junit.Assert.assertEquals(Assert.java:118)
    at org.junit.Assert.assertEquals(Assert.java:144)
    at com.fideuram.dbmanager.PucManagerTest.getNavInfoTest(PucManagerTest.java:90)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

为什么两者都代表ame 1.0值？如何解决此问题以通过测试？

Answer 1

原因是如何BigDecimal equals实施.BigDecimal.ONE被构造成 new BigDecimal(BigInteger.ONE, 1, 0, 1).equals方法以下列方式实现(来自JDK源代码):

public boolean equals(Object x) {
    if (!(x instanceof BigDecimal))
        return false;
    BigDecimal xDec = (BigDecimal) x;
    if (x == this)
        return true;
    if (scale != xDec.scale)
        return false;
    long s = this.intCompact;
    long xs = xDec.intCompact;
    if (s != INFLATED) {
        if (xs == INFLATED)
            xs = compactValFor(xDec.intVal);
        return xs == s;
    } else if (xs != INFLATED)
        return xs == compactValFor(this.intVal);

    return this.inflated().equals(xDec.inflated());
}

所以BigDecimals只有两个人具有相同的比例才是平等的.ONE比例小于返回的比例BigDecimal因此它们不相等.

我看到一些答案说,你可以采取的floatValue的BigDecimal.好吧,你做不到.BigDecimal在处理更大的数字时使用,所以在这种情况下它会起作用,但是这是一个糟糕的模式.

但幸运的是我们可以使用compareTo方法!

assertTrue(tirAliquotaRamoI.getAliquota().compareTo(expectedObject.getAliquota()) == 0);

它不完美但会起作用!

Answer 2

它看起来像他们有不同的规模.

尝试的compareTo:

 assertEquals(0, tirAliquotaRamoI.compareTo(expectedObject.getAliquota());

或者如果您关心匹配比例,那么您将不得不使用setScale(int newScale)更改任一对象的比例以匹配另一个.

希望有所帮助.

感谢@David SN的修正.

Answer 3

BigDecimal比较也总是使用比例,因此您的测试失败.

有关详细信息,请参阅Javadoc.

如果您只对值而不是比例感兴趣,那么在比较时请考虑使用stripTrailingZeros().

assertEquals(
    tirAliquotaRamoI.getAliquota().stripTrailingZeros(),
    expectedObject.getAliquota().stripTrailingZeros()
);