Both the Mockito as PowerMockito class have the functions doNothing() and mock() in common (and perhaps some other functions too).
When I look at the source code, the only difference between the implementations is the reference to MOCKITO_CORE or POWERMOCKITO_CORE, and the return type.
For example:
public static PowerMockitoStubber doNothing() {
return POWERMOCKITO_CORE.doAnswer(new DoesNothing());
}
and
public static Stubber doNothing() {
return MOCKITO_CORE.doAnswer(new DoesNothing());
}
Is there any real substantial difference between these implementations?
I assume not, but then again, why would there be two implementations?
PowerMockito, in addition to Mockito capabilities, allows to mock private and static methods. If this is something you might use, you should switch to PowerMockito.
Related
public static ResponseBean call(Bean bean) throws Exception {
// statements...
IgnoreCall.ignoreMethodCall(bean);
// statements...
// return
}
With the code snippet above, is it possible to test the method ignoring invocation of IgnoreCall.ignoreMethod(Bean) without needing to place the entire statement under a boolean condition?
Here's the unit test code snippet:
#RunWith(PowerMockRunner.class)
#PrepareTest
public ClassHelperTest {
#Test
public void testCall() throws Excpetion {
// stubbing...
ResponseBean responseBean = ClassHelper.call(bean);
// verify/ies
// assert/s
}
}
Notes:
Refactoring ClassHelper.call(Bean) should be avoided. Even with a bad OO design, refactoring is costly.
Method signature is locked unless another pattern is applicable for replacement.
Tried using Mockito.when and PowerMockito.when on the target static method, stubbing didn't work on run-time debug.
As your comments indicate that changing your production code is not possible, you "simply" have to dive into the static-mocking aspects of PowerMock; as outlined here for example.
Basically you need to enable IgnoreCall for static mocking; and then you make calls to ignoreMethodCall() a no-op.
But as you keep asking: the core problem with your question is the fact that you want to mock out a static method that is void. I have a complete example below, but before that some explanations.
The point is: you call a method for two reasons:
It has a side effect
It returns a value, and maybe, causes a side effect, too
A void method can only be called for side effects. And the thing is: when you do static mocking, then that works on class level.
Meaning: you instruct PowerMock to "prevent" any of the static methods of some class from execution; you simply "erase" the side effects of all those static methods! So, by telling PowerMock to do those static mocks, all void methods are already "gone".
But as said, you might also call methods for their return value. And then is when the when() method of Mockito kicks in. You use that method to say: when that value-returning method is invoked, then do this or that.
Long story short; here is a [mcve] using the elements you asked for:
package ghostcat.test;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
class IgnoreCall {
public static void ignoreMethodCall(Object o) {
System.out.println("SHOULD NOT SHOW UP: " + o);
}
}
class CuT {
public static Object call(Object bean) {
System.out.println("statement1");
IgnoreCall.ignoreMethodCall(bean);
System.out.println("statement2");
return "whatever";
}
}
#RunWith(PowerMockRunner.class)
#PrepareForTest(IgnoreCall.class)
public class PMTest {
#Test
public void test() {
PowerMockito.mockStatic(IgnoreCall.class);
CuT.call("yeha");
}
}
As in your example ... there is IgnoreCall; used within that a static method that I just called "call".
This prints:
statement1
statement2
When I go in and comment out
// PowerMockito.mockStatic(IgnoreCall.class);
It prints:
statement1
SHOULD NOT SHOW UP: yeha
statement2
So, a simple example that should tell you exactly what you need to do.
I worked with eclipse neon, IBM java8 JDK, and simply imported all the JARs from powermock-mockito-junit-1.6.6.zip into my test project.
I have a class which has both static and non static methods and would like to write unit test cases for the same.
ClassA{
static getInstance()
{
// to do logic
}
void log()
{
system.out.print();
}
}
And the test case for classA is
ClassTest
{
public void setup()
{
PowerMockito.mockStatic(ClassA.class);
mockA = PowerMockito.mock(ClassA.class);
Mockito.when(ClassA.getInstance("user")).thenReturn(mockA);
Mockito.doNothing().when(mockA).log(Mockito.anyString(), Mockito.anyString(), Mockito.any(Exception.class), Mockito.anyMap());
enter code here
}
}
When i call log method, i am getting exception. How do we mock this?
Serious answer: don't do that.
Simply avoid writing production code that requires PowerMock; for example because you are mixing in calls to static methods.
Typically, a "need for PowerMock" directly translates to: your design needs to be improved!
You will find pretty quickly that PowerMock creates more problems that it is solving. Thus: avoid using it.
Hi I am new to unit testing. Is it possible to access methods that are private?
A very simple example
ObjectA
----------
File file;
private void setupFile (){
//do something
file = "C:\file.dat"
}
In TestCase
File sth = ObjectA.setupFile();
assertNotNull(sth);
I am unable to test whether the file variable is null in method ObjectA.setup()
as I cannot run ObjectA.setupFile()
I am not sure about whether doing like this make sense in terms of unit testing.
So is that a better practice to write every method returning sth and set them public for easier unit testing?
Thanks in advance
In general, you should avoid changing the access of a method/field to enable testing. If you do this then you risk developers using the method directly.
However, if you do need to, then making it protected as Deco says is a good way, so it's accessible from the JUnit tests. If you do this, make sure that it is well documented that this is an method for internal use.
A better way is to test the behaviour of the public methods; you shouldn't care about internal implementation details of a class, so you should only be testing public methods. It's hard to tell from your code, but presumably, the setupFile() has effects later on other methods, so you can test those effects, not the fact that file is not null.
External dependencies (such as dependencies on file system, environment variables) can be worked around in your tests, or injected directly into the class. For the general principle, see my answer to How to test code dependent on environment variables using JUnit?
If it is not absolutely necessary to have the method as private, you can have it as package private (i.e. default access) so that you can call it directly in a JUnit test.
Package private methods can only be used in the package that they are declared, and do not become part of the API of the class. You declare a method package private by putting no modifier on it's declaration.
Here's an example to demonstrate:
public class MyClass() {
int foo;
public MyClass() {
this.foo = 0;
}
void notSoComplexCalculationMethod(int a) {
foo = a * 2;
}
//Other methods here . . .
}
public class MyClassTest extends TestCase {
private MyClass myClass;
protected void setUp() {
super.setUp();
myClass = new MyClass();
}
public void testNotSoComplexCalculationMethod() {
int a = 2;
assertEquals(4, myClass.notSoComplexCalculationMethod(a));
//Unit test passes, yay! Now you've tested a package private method.
}
}
It seems impossible to create an object using its default constructor when there is a static .New() method defined on the class:
.NET class:
public class Tester
{
public static void New()
{
Console.WriteLine("In Tester.New()");
}
public Tester()
{
Console.WriteLine("In constructor");
}
}
IronRuby code:
Tester.new
Tester.New
Both of these lines call Tester.New(), not the constuctor. It seems impossible to call the constructor of the Tester class.
Is there a workaround, or is this a bug?
The first one is just an unavoidable ambiguity. If you want to make CLI classes look like Ruby classes, you have no choice but to map the constructor to a new method. So, if you have both a real new method and a synthesized one which maps to a constructor, whatever you do, either the synthetic method shadows the real one or the other way around. Either way, you lose.
That's why all CLI classes have a synthetic clr_new method:
Tester.clr_new
# In constructor
I'm trying to figure out when it would be appropriate for a class to have both static and non-static functions. AKA:
$obj = new ClassA;
$obj->doOOPStuff();
$something = ClassA::doStaticStuff();
Note: This example is done in PHP, however the question is language agnostic .
It seems that if you have a class that is meant to be instantiated, any functions that can be called statically, most likely belong in another class.
Is there any viable cases where I would have a class that used static AND non-static members?
One example: when Creation has to happen in a specific way.
class Foo {
public:
static Foo* Create(...params...);
private:
Foo();
};
Consider String class in .NET. It contains a non-static Split method which breaks some instance into a string[] and a static Join method, which takes a string[] and transform it into a string again.
A static method is applicable when you don't need to keep any state. So Math.Sin() just depends on its parameters and, given same parameters, output will always be the same. A non-static method can have different behavior is called multiple times, as it can keep a internal state.
If the functionality provided by static methods is relevant to that class and its objects, why not. It is pretty common.
Static method are most often factory methods
public class MyClass {
public static MyClass createMyClass(int a, double b) {..}
public static MyClass createSubclassOfMyClass(int c, boolean cond) {..}
public int calculateThis();
public double calculateThat();
}
Another use is to access some property that is logically bound that that class, but not separately to instances. For example - a cache:
(Note - of course synchronization should be taken into account in this example)
public class MyClass {
public static final Cache cache = new Cache();
public static void putInCacheIfNeeded(Object obj) {..}
public static void replaceInCache(Object obj) {..}
public void doSomethingCacheDependend(Object obj) {
if (something) {
MyClass.putInCacheIfNeeded(obj);
} else {
MyClass.replaceInCache(obj);
}
}
}
(Java language for the examples)
Imagine your constructor has two overloads that both are strings:
public class XmlDocument
{
public static XmlDocument CreateFromFile(string filePath);
public static XmlDocument CreateFromXml(string xml);
}
The static function can provide meaningful name to the constructor.
$dialog = DialogFoo::createOpenDialog();
$dialog = DialogFoo::createDocumentOpenDialog();
$dialog = DialogFoo::createImageOpenDialog();
It could also be used to enforce Singleton pattern.
$dialog = DialogFoo::getInstance()
Static class members are most useful where everything must either be in an object or be in a global scope; they are less useful in a language such as Python that supports module-level scopes.
I use static methods to instantiate new objects when I dont want the to give access to the constructor. I ensure that any necessary preconditions are carried out on the class before creating and object. In this example I have a counter to return how many objects are created, if I have 10 objects I prevent any more from being instantiated.
class foo {
private:
static int count;
foo() {}
public:
static foo bar() {
count++;
if (count<=10){
return new foo;
} else {
return null;
}
Let's assume a class has instance methods, here are some good use case for having static methods too:
For static utility methods
Such methods apply to any instance, for example String.format(String, Object...) in Java.
Use them when you don't want to create a specific instance for the job.
For static factory methods
Factory methods are methods that simply instantiate objects like the getInstance() and valueOf() methods in the Java API. getInstance() is the conventional instantiation method in singletons while valueOf() are often type-conversion methods, like in String.valueOf(int).
Use them to improve performance via object-caching, in interface-based frameworks (like the Collections Framework in Java) where you may want to return a subtype, to implement singletons (cough).
In general, static functions produce functionality highly related to class itself. It may be some helper functions, factory methods etc. In this case all functionality contains in one place, it correspond to DRY principle, increases cohesion and reduces coupling.