blocks|key|2746212|text|免责声明：在各种不同的帖子上找了很久之后，我找到了答案。这是可以做到的，但普遍的共识是它不是很安全，但考虑到您只在单元测试中这样做，我认为您接受这些风险:)|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|2746213|2746214|答案不是嘲笑，因为大多数嘲笑不允许你进入决赛。答案有点“老生常谈”，当Java调用的是核心java.lang.reflect.Field和java.lang.reflect.Modifier类(反射)时，您实际上是在修改私有字段。看着this+answer，我能够拼凑出你测试的其余部分，而不需要模拟来解决你的问题。|CODE|2746215|这个答案的问题在于，我在尝试修改variable时遇到了NoSuchFieldException。有关如何访问私有字段而不是公共字段，another+post提供了帮助。|2746216|解释反射/字段操作：|2746217|因为Mocking不能处理final，所以我们最终要做的是深入到字段本身的根中。当我们使用Field操作(反射)时，我们在寻找类/对象内部的特定变量。一旦Java找到它，我们就得到它的“修饰符”，它告诉变量它有什么约束/规则，比如final，static，private，public等等。我们找到正确的变量，然后告诉代码它是可访问的，这允许我们改变这些修饰符。一旦我们改变了根部的“访问”以允许我们操作它，我们就关闭了它的“最终”部分。然后，我们可以更改该值并将其设置为所需的任何值。|2746218|简单地说，我们正在修改变量以允许我们更改其属性，删除final的属性，然后更改值，因为它不再是final。有关这方面的详细信息，请访问check+out+the+post+where+the+idea+came+from。|2746219|所以我们一步一步地传入我们想要操作的变量，然后...|2746220|//+Mark+the+field+as+public+so+we+can+toy+with+it
field.setAccessible(true);
//+Get+the+Modifiers+for+the+Fields
Field+modifiersField+=+Field.class.getDeclaredField("modifiers");++
//+Allow+us+to+change+the+modifiers
modifiersField.setAccessible(true);
+//+Remove+final+modifier+from+field+by+blanking+out+the+bit+that+says+"FINAL"+in+the+Modifiers
modifiersField.setInt(field,+field.getModifiers()+&+~Modifier.FINAL);
//+Set+new+value
field.set(null,+newValue);+|code-block|syntax|javascript|2746221|2746222|将所有这些整合到一个新的超级答案中。|2746223|@RunWith(PowerMockRunner.class)
@PrepareForTest()
class+PrivateStaticFinalTest+{
++++@Test
++++public+void+testMethod(){
++++++try+{
++++++++setFinalStatic(PrivateStaticFinal.class.getDeclaredField("variable"),+Integer.valueOf(100));
++++++}+
++++++catch+(SecurityException+e)+{fail();}
++++++catch+(NoSuchFieldException+e)+{fail();}
++++++catch+(Exception+e)+{fail();}
++++++assertEquals(PrivateStaticFinal.method(),+Integer.valueOf(101));
++++}

++++static+void+setFinalStatic(Field+field,+Object+newValue)+throws+Exception+{
++++++++field.setAccessible(true);
++++++++//+remove+final+modifier+from+field
++++++++Field+modifiersField+=+Field.class.getDeclaredField("modifiers");
++++++++modifiersField.setAccessible(true);
++++++++modifiersField.setInt(field,+field.getModifiers()+&+~Modifier.FINAL);
++++++++field.set(null,+newValue);
++++}
}|2746224|更新上面的解决方案只适用于那些在静态block.When声明和初始化常量的同时初始化的常量，编译器可能会内联它，此时对原始值的任何更改都会被忽略。|2746225|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/2474017/using-reflection-to-change-static-final-file-separatorchar-for-unit-testing|1|https://stackoverflow.com/questions/15420968/nosuchfieldexception-when-field-exists|2|http://www.javaspecialists.eu/archive/Issue161.html^0|0|5|0|0|19|N|1X|Q|39|B|0|0|G|8|S|K|1V|C|1|0|2|8|0|19|5|37|5|3D|6|3K|7|3S|6|0|Q|5|1B|5|1V|17|2|0|0|0|0|0|0|0|2|0^^$0|@$1|2|3|4|5|6|7|1H|8|@$9|1I|A|1J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|1K|8|@]|D|@]|E|$]]|$1|G|3|H|5|6|7|1L|8|@$9|1M|A|1N|B|I]|$9|1O|A|1P|B|I]]|D|@$9|1Q|A|1R|1|1S]]|E|$]]|$1|J|3|K|5|6|7|1T|8|@$9|1U|A|1V|B|I]|$9|1W|A|1X|B|I]]|D|@$9|1Y|A|1Z|1|20]]|E|$]]|$1|L|3|M|5|6|7|21|8|@$9|22|A|23|B|C]]|D|@]|E|$]]|$1|N|3|O|5|6|7|24|8|@$9|25|A|26|B|I]|$9|27|A|28|B|I]|$9|29|A|2A|B|I]|$9|2B|A|2C|B|I]|$9|2D|A|2E|B|I]]|D|@]|E|$]]|$1|P|3|Q|5|6|7|2F|8|@$9|2G|A|2H|B|I]|$9|2I|A|2J|B|I]]|D|@$9|2K|A|2L|1|2M]]|E|$]]|$1|R|3|S|5|6|7|2N|8|@]|D|@]|E|$]]|$1|T|3|U|5|V|7|2O|8|@]|D|@]|E|$W|X]]|$1|Y|3|-4|5|6|7|2P|8|@]|D|@]|E|$]]|$1|Z|3|10|5|6|7|2Q|8|@]|D|@]|E|$]]|$1|11|3|12|5|V|7|2R|8|@]|D|@]|E|$W|X]]|$1|13|3|14|5|6|7|2S|8|@$9|2T|A|2U|B|C]]|D|@]|E|$]]|$1|15|3|-4|5|6|7|2V|8|@]|D|@]|E|$]]]|16|$17|$5|18|19|1A|E|$1B|1C]]|1D|$5|18|19|1A|E|$1B|1E]]|1F|$5|18|19|1A|E|$1B|1G]]]]

Disclaimer: After a lot of hunting around on various threads I have found an answer. It can be done, but the general concensus is that it is not very safe but seeing as how you are doing this ONLY IN UNIT TESTS, I think you accept those risks :)

<hr>

The answer is not Mocking, since most Mocking does not allow you to hack into a final. The answer is a little more "hacky", where you are actually modifying the private field when Java is calling is core <code>java.lang.reflect.Field</code> and <code>java.lang.reflect.Modifier</code> classes (reflection). Looking at <a href="https://stackoverflow.com/questions/2474017/using-reflection-to-change-static-final-file-separatorchar-for-unit-testing">this answer</a> I was able to piece together the rest of your test, without the need for mocking that solves your problem.

The problem with that answer is I was running into <code>NoSuchFieldException</code> when trying to modify the <code>variable</code>. The help for that lay in <a href="https://stackoverflow.com/questions/15420968/nosuchfieldexception-when-field-exists">another post</a> on how to access a field that was private and not public.

Reflection/Field Manipulation Explained:

Since Mocking cannot handle final, instead what we end up doing is hacking into the root of the field itself. When we use the <code>Field</code> manipulations (reflection), we are looking for the specific variable inside of a class/object. Once Java finds it we get the "modifiers" of it, which tell the variable what restrictions/rules it has like <code>final</code>, <code>static</code>, <code>private</code>, <code>public</code>, etc. We find the right variable, and then tell the code that it is accessible which allows us to change these modifiers. Once we have changed the "access" at the root to allow us to manipulate it, we are toggling off the "final" part of it. We then can change the value and set it to whatever we need.

To put it simply, we are modifying the variable to allow us to change its properties, removing the propety for <code>final</code>, and then changing the value since it is no longer <code>final</code>. For more info on this, <a href="http://www.javaspecialists.eu/archive/Issue161.html" rel="noreferrer">check out the post where the idea came from</a>.

So step by step we pass in the variable we want to manipulate and... 

<pre><code>// Mark the field as public so we can toy with it
field.setAccessible(true);
// Get the Modifiers for the Fields
Field modifiersField = Field.class.getDeclaredField("modifiers"); 
// Allow us to change the modifiers
modifiersField.setAccessible(true);
 // Remove final modifier from field by blanking out the bit that says "FINAL" in the Modifiers
modifiersField.setInt(field, field.getModifiers() &amp; ~Modifier.FINAL);
// Set new value
field.set(null, newValue); 
</code></pre>

<hr>

Combining this all into a new SUPER ANSWER you get.

<pre><code>@RunWith(PowerMockRunner.class)
@PrepareForTest()
class PrivateStaticFinalTest {
 @Test
 public void testMethod(){
 try {
 setFinalStatic(PrivateStaticFinal.class.getDeclaredField("variable"), Integer.valueOf(100));
 } 
 catch (SecurityException e) {fail();}
 catch (NoSuchFieldException e) {fail();}
 catch (Exception e) {fail();}
 assertEquals(PrivateStaticFinal.method(), Integer.valueOf(101));
 }

 static void setFinalStatic(Field field, Object newValue) throws Exception {
 field.setAccessible(true);
 // remove final modifier from field
 Field modifiersField = Field.class.getDeclaredField("modifiers");
 modifiersField.setAccessible(true);
 modifiersField.setInt(field, field.getModifiers() &amp; ~Modifier.FINAL);
 field.set(null, newValue);
 }
}
</code></pre>

Update
The above solution will work only for those constants which is initialized in static block.When declaring and initializing the constant at the same time, it can happen that the compiler inlines it, at which point any change to the original value is ignored.

what is the absolute minimal mocking that must be done to pass this test?

code:

<pre><code>class PrivateStaticFinal {
 private static final Integer variable = 0;
 public static Integer method() { return variable + 1; }
}
</code></pre>

test:

<pre><code>@RunWith(PowerMockRunner.class)
@PrepareForTest(PrivateStaticFinal.class)
class PrivateStaticFinalTest {
 @Test
 public void testMethod() {
 //TODO PrivateStaticFinal.variable = 100
 assertEquals(PrivateStaticFinal.method(), 101);
 }
}
</code></pre>

related: <a href="https://stackoverflow.com/questions/19426999/mock-private-static-final-variables-in-the-testing-class">Mock private static final variables in the testing class</a> (no clear answer)

PowerMock: mock out private static final variable, a concrete example

单元测试

编译器

Java

要通过此测试，必须执行的绝对最小模拟是什么？代码：class PrivateStaticFinal {    private static final Integer variable = 0;    public static Integer method() { return variable + 1; }}测试：...

问PowerMock:模拟私有静态最终变量，一个具体的例子
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