We Keep Coding

Mocking Java Constant variables (public static) using Mockito/JUnit

I need to mock the constant variable in order to test one of my method. How can I do it with Mokito and Junit.
#Component( "mybean" )
#org.springframework.context.annotation.Scope( value="session" )
public class MyBean {
Public void methodToBeTested() {
if (!AppConst.SOME_CONST.equals(obj.getCostCode())) {
// some logic
}
}
}
AppConst class
#Configuration
public class AppConst
{
public static String SOME_CONST;
public static String HOST_URL;
#PostConstruct
public void postConstruct()
{
SOME_CONST = "My Code";
HOST_URL = "Some URL";
}
}
So, from my junit test class, how can I mock the AppConst and it's variables? Now, when I run it, i hit a nullpointer error.
Can this be done with powermock? if yes please give some sample
Mockito version I use.
compile "org.mockito:mockito-all:1.9.5"
compile "org.powermock:powermock-mockito-release-full:1.6.1"

Instead of mocking there would be another solution to be able to test it:
public void methodToBeTested(SomeObject obj) {
performLogic(AppConst.SOME_CONST, obj);
}
boolean performLogic(String check, SomeObject testObj) {
if (!check.equals(obj.getCostCode())) {
// some logic
return true;
}
return false;
}
That way you can test two things, both combined show you that your code works as intended:
public void testMethodToBeTested() {
MyBean mb = new MyBean() {
#Override
void performLogic(String check, SomeObject testObj) {
assertSame("check constant is passed", AppConst.SOME_CONST, check);
}
}
mb.methodToBeTested(new SomeObject());
mb = new MyBean();
SomeObject so = createSomeTestObject("My Code"); // not the actual constant but an equal String
assertFalse("check some logic not occurred", mb.performLogic("My Code", so));
so = createSomeTestObject("Not the constant");
assertFalse("check some logic not occurred", mb.performLogic("Not the constant", so));
assertTrue("check some logic occurred", mb.performLogic("My Code", so));
// additional tests covering the actual logic
}
Another solution could be putting the condition of the if-statement into its own method, e.g. shouldLogicOccurr(String check) and test that method individually.
In other words: Sometimes it's necessary to refactor your code to make tests easier or sometimes even possible at all. A good side effect is the next time you implement something you already have testability in mind and create your code suitable for this in the first place.
Mocking is a good way to get things under test that use third party libraries that can't be changed and have too many dependencies to be set up but if you end up using that for your own code you've got a design issue.

First stub is called when adding an additional stub

I have the following object which I want to test:
public class MyObject {
#Inject
Downloader downloader;
public List<String> readFiles(String[] fileNames) {
List<String> files = new LinkedList<>();
for (String fileName : fileNames) {
try {
files.add(downloader.download(fileName));
} catch (IOException e) {
files.add("NA");
}
}
return files;
}
}
This is my test:
#UseModules(mockTest.MyTestModule.class)
#RunWith(JukitoRunner.class)
public class mockTest {
#Inject Downloader downloader;
#Inject MyObject myObject;
private final String[] FILE_NAMES = new String[] {"fail", "fail", "testFile"};
private final List<String> EXPECTED_FILES = Arrays.asList("NA", "NA", "mockContent");
#Test
public void testException() throws IOException {
when(downloader.download(anyString()))
.thenThrow(new IOException());
when(downloader.download("testFile"))
.thenReturn("mockContent");
assertThat(myObject.readFiles(FILE_NAMES))
.isEqualTo(EXPECTED_FILES);
}
public static final class MyTestModule extends TestModule {
#Override
protected void configureTest() {
bindMock(Downloader.class).in(TestSingleton.class);
}
}
}
I am overwriting the anyString() matcher for a specific argument. I am stubbing the download() method so that it returns a value for a specific argument and otherwise throws an IOException which gets handled by MyObject.readFiles.
The weird thing here is that the second stub (downloader.download("testFile")) throws the IOException set in the first stub (downloader.download(anyString())). I have validated that by throwing a different exception in my first stub.
Can someone explain me why the exception is thrown when adding an additional stub? I thought that creating a stub does not call the method/other stubs.

The problem is that when you write
when(downloader.download("testFile")).thenReturn("mockContent");
the first thing to be called is downloader.download, which you've already stubbed to throw an exception.
The solution is to use the slightly more versatile stubbing syntax that Mockito provides. This syntax has the advantage that it doesn't call the actual method when stubbing.
doThrow(IOException.class).when(downloader).download(anyString());
doReturn("mock content").when(downloader).download("test file");
I have listed other advantages of this second syntax, in my answer here

I thought that creating a stub does not call the method/other stubs.
This assumption is wrong, because stubbing is calling the mocks methods. Your test methods are still plain java!
Since stubbing for anyString will overwrite stubbing for any specific string you will either have to write two tests or stub for two specific arguments:
when(downloader.download("fail")).thenThrow(new IOException());
when(downloader.download("testFile")).thenReturn("mockContent");
Mockito is a very sophisticated piece of code that tries its best so that you can write
when(downloader.download(anyString())).thenThrow(new IOException());
which means “when the downloaders mock download method is called with anyString argument thenThrow an IOException” (i.e. it can be read from left to right).
However, since the code is still plain java, the call sequence actually is:
String s1 = anyString(); // 1
String s2 = downloader.download(s1); // 2
when(s2).thenThrow(new IOException()); // 3
Behind the scenes, Mockito needs to do this:
register an ArgumentMatcher for any String argument
register a method call download on the downloader mock where the argument is defined by the previously registered ArgumentMatcher
register an action for the previously registered method call on a mock
If you now call
... downloader.download("testFile") ...
the downloader mock checks whether there is an action register for "testFile" (there is, since there is already an action for any String) and accordingly throws the IOException.

Your 2nd mock statement is getting overriden by the first mock statement (because both mock statements are passing a String argument). If you want to cover try as well as catch back through your mock test then write 2 different test cases.

How do you expect and verify a private void method call using PowerMockito and TestNG?

I need to write unit tests against a pre-existing code base using TestNG, Mockito and now PowerMockito, to test private and static methods more easily. I am currently trying to write a test against a private void method in a class that we are testing, but am unable to figure it out. In the normal PowerMock API there are methods called replayAll(), verifyAll(), and expectLastCalled(), which are suitable for most purposes. I just can't find good docs that explain how to do it the PowerMockito way. Any explanations or insights on this would be much appreciated.
Method to test:
private void pVMethod(Type param) throws Exception {
param.setA(StaticClass.methodA().toString());
param.setB(StaticClass.methodB().toString());
// getMemo(String label) is in a public class in same package
param.setC(getMemo("memo.provider"));
param.setD(getMemo("memo.item"));
try {
param.setTimestamp(DataTypeFactory.newInstance().newXMLGregorianCalendar(newjava.util.GregorianCalendar()));
} catch (SomeException e) {
...
throw new Exception();
}
}
test attempt:
#Test(expectedExceptions = Exception.class)
public void pVMethod() throws Exception {
TestClass testMock = mock(TestClass.class);
Exception exception = mock(Exception.class);
// StaticClass staticClassMock = mock(StaticClass.class); ??
mockStatic(StaticClass.class);
// when(..) and thenReturn(..) are static imports from PowerMockito library
when(StaticClass.methodA()).thenReturn("stubStringA");
when(StaticClass.methodB()).thenReturn("stubStringB");
doThrow(exception).when(param).setTimestamp(Mockito.any(XMLGregorianCalendar.class));
// Docs say method name can be inferred via reflection
Whitebox.invokeMethod(tested, event);
// this is where things are hairy. testedSpy is defined at the top level
verifyPrivate(testedSpy).pVMethod(testMock);
}

Ok, here is the answer:
In PowerMockito, if you want to verify the behavior of a private void method you use the verifyPrivate() method, but you have to do it like this:
verifyPrivate(tested).invoke("privateMethodName", argument);
Notice the use of the invoke method, missing from the last line of the OP.
NOTE: You do not have to use a doNothing().when(mock.privateMethod()) statement, because void methods in mock objects don't do anything by default.
example taken from here

Mark unit test as an expected failure in JUnit

How can I mark a test as an expected failure in JUnit 4?
In this case I want to continue to run this test until something is patched upstream. Ignoring the test goes a little too far, as then I might forget about it. I may be able to add an #expected annotation and catch the exception thrown by assertThat, but that also seems to lie about the expected behavior.
Here's what my current test looks like:
#Test
public void unmarshalledDocumentHasExpectedValue()
{
doc = unmarshaller.unmarshal(getResourceAsStream("mydoc.xml"));
final ST title = doc.getTitle();
assertThat(doc.getTitle().toStringContent(), equalTo("Expected"));
}
That assert should succeed, but because of an upstream bug it doesn't. Yet, that test is correct; it should succeed. Virtually all the alternatives that I've found are misleading. Right now I think #Ignore("This test should pass once fixed upstream") is my best bet, but I still have to remember to come back to it. I'd prefer that the test run.
In Python I can use the expectedFailure decorator:
class ExpectedFailureTestCase(unittest.TestCase):
#unittest.expectedFailure
def test_fail(self):
self.assertEqual(1, 0, "broken")
With Qt's QTestLib in C++, you can use QEXPECT_FAIL:
QEXPECT_FAIL("", "Will be fixed next version", Continue);
QCOMPARE(i, 42);
In both cases above, the unit test runs which is what I'm hoping to have happen. Am I missing something in JUnit?

I'm not quite getting the specifics of your scenario, but here's how I generally test for expected failure:
The slick new way:
#Test(expected=NullPointerException.class)
public void expectedFailure() {
Object o = null;
o.toString();
}
for older versions of JUnit:
public void testExpectedFailure() {
try {
Object o = null;
o.toString();
fail("shouldn't get here");
}
catch (NullPointerException e) {
// expected
}
}
If you have a bunch of things that you want to ensure throw an exception, you may also want to use this second technique inside a loop rather than creating a separate test method for each case. If you were just to loop through a bunch of cases in a single method using expected, the first one to throw an exception would end the test, and the subsequent cases wouldn't get checked.

What about explicitly expecting an AssertionError?
#Test(expected = AssertionError.class)
public void unmarshalledDocumentHasExpectedValue() {
// ...
}
If you're reasonably confident that only the JUnit machinery within the test would raise AssertionError, this seems as self-documenting as anything.
You'd still run the risk of forgetting about such a test. I wouldn't let such tests into version control for long, if ever.

I'm assuming here that you want the test to pass if your assert fails, but if the assert succeeds, then the test should pass as well.
The easiest way to do this is to use a TestRule. TestRule gives the opportunity to execute code before and after a test method is run. Here is an example:
public class ExpectedFailureTest {
public class ExpectedFailure implements TestRule {
public Statement apply(Statement base, Description description) {
return statement(base, description);
}
private Statement statement(final Statement base, final Description description) {
return new Statement() {
#Override
public void evaluate() throws Throwable {
try {
base.evaluate();
} catch (Throwable e) {
if (description.getAnnotation(Deprecated.class) != null) {
// you can do whatever you like here.
System.err.println("test failed, but that's ok:");
} else {
throw e;
}
}
}
};
}
}
#Rule public ExpectedFailure expectedFailure = new ExpectedFailure();
// actually fails, but we catch the exception and make the test pass.
#Deprecated
#Test public void testExpectedFailure() {
Object o = null;
o.equals("foo");
}
// fails
#Test public void testExpectedFailure2() {
Object o = null;
o.equals("foo");
}
}
First, note that the first method is marked as #Deprecated. I'm using this as a marker for the method for which I want to ignore any assertion failures. You can do whatever you like to identify the methods, this is just an example.
Next, in the ExpectedFailure#apply(), when I do the base.evaluate(), I'm catching any Throwable (which includes AssertionError) and if the method is marked with the annotation #Deprecated, I ignore the error. You can perform whatever logic you like to decide whether you should ignore the error or not, based on version number, some text, etc. You can also pass a dynamically determined flag into ExpectedFailure to allow it to fail for certain version numbers:
public void unmarshalledDocumentHasExpectedValue() {
doc = unmarshaller.unmarshal(getResourceAsStream("mydoc.xml"));
expectedFailure.setExpectedFailure(doc.getVersionNumber() < 3000);
final ST title = doc.getTitle();
assertThat(doc.getTitle().toStringContent(), equalTo("Expected"));
}
For further examples, see ExternalResource, and ExpectedException
Ignoring an expected failure test rather than passing it
If you want to mark you tests as Ignored rather than Success, it becomes a bit more complex, because tests are ignored before they are executed, so you have to retrospectively mark a test as ignored, which would involve constructing your own Runner. To give you a start, see my answer to How to define JUnit method rule in a suite?. Or ask another question.

One option is mark the test as #Ignore and put text in there that is a bug perhaps and awaiting a fix. That way it won't run. It will then become skipped. You could also make use of the extensions to suit your need in a potentially different way.

I've taken Matthew's answer a step further and actually implemented an #Optional annotation you could use instead of the #Deprecated marker annotation he mentions in his answer. Although simple, I'll share the code with you, maybe it's of help for someone:
#Target(ElementType.METHOD)
#Retention(RetentionPolicy.RUNTIME)
#Documented
public #interface Optional {
/**
* Specify a Throwable, to cause a test method to succeed even if an exception
* of the specified class is thrown by the method.
*/
Class<? extends Throwable>[] exception();
}
With a simple alteration of Matt's ExpectedFailure class:
public class ExpectedFailure implements TestRule {
#Override
public Statement apply(final Statement base, final Description description) {
return statement(base, description);
}
private Statement statement(final Statement base, final Description description) {
return new Statement() {
#Override
public void evaluate() throws Throwable {
try {
base.evaluate();
} catch (Throwable e) {
// check for certain exception types
Optional annon = description.getAnnotation(Optional.class);
if (annon != null && ArrayUtils.contains(annon.exception(), e.getClass())) {
// ok
} else {
throw e;
}
}
}
};
}
}
You can now annotate your test method with #Optional and it will not fail, even if the given type of exception is raised (provide one or more types you would like the test method to pass):
public class ExpectedFailureTest {
#Rule public ExpectedFailure expectedFailure = new ExpectedFailure();
// actually fails, but we catch the exception and make the test pass.
#Optional(exception = NullPointerException.class)
#Test public void testExpectedFailure() {
Object o = null;
o.equals("foo");
}
}
[UPDATE]
You could also rewrite your tests using JUnit's org.junit.Assume instead of the tradtional org.junit.Assert, if you want your tests to pass even if the assumption does not hold.
From Assume's JavaDoc:
A set of methods useful for stating assumptions about the conditions in which a test is meaningful.A failed assumption does not mean the code is broken, but that the test provides no useful information. The default JUnit runner treats tests with failing assumptions as ignored.
Assume is available since JUnit 4.4

Use mocked upstream class if possible. Stub it with correct result. Optionally, replace mock with real object after bug is fixed.

How to mock a String using mockito?

I need to simulate a test scenario in which I call the getBytes() method of a String object and I get an UnsupportedEncodingException.
I have tried to achieve that using the following code:
String nonEncodedString = mock(String.class);
when(nonEncodedString.getBytes(anyString())).thenThrow(new UnsupportedEncodingException("Parsing error."));
The problem is that when I run my test case I get a MockitoException that says that I can't mock a java.lang.String class.
Is there a way to mock a String object using mockito or, alternatively, a way to make my String object throw an UnsupportedEncodingException when I call the getBytes method?
Here are more details to illustrate the problem:
This is the class that I want to test:
public final class A {
public static String f(String str){
try {
return new String(str.getBytes("UTF-8"));
} catch (UnsupportedEncodingException e) {
// This is the catch block that I want to exercise.
...
}
}
}
This is my testing class (I'm using JUnit 4 and mockito):
public class TestA {
#Test(expected=UnsupportedEncodingException.class)
public void test(){
String aString = mock(String.class);
when(nonEncodedString.getBytes(anyString())).thenThrow(new UnsupportedEncodingException("Parsing error."));
A.f(aString);
}
}

The problem is the String class in Java is marked as final, so you cannot mock is using traditional mocking frameworks. According to the Mockito FAQ, this is a limitation of that framework as well.

How about just creating a String with a bad encoding name? See
public String(byte bytes[], int offset, int length, String charsetName)
Mocking String is almost certainly a bad idea.

If all you are going to do in your catch block is throw a runtime exception then you can save yourself some typing by just using a Charset object to specify your character set name.
public final class A{
public static String f(String str){
return new String(str.getBytes(Charset.forName("UTF-8")));
}
}
This way you aren't catching an exception that will never happen just because the compiler tells you to.

As others have indicated, you can't use Mockito to mock a final class. However, the more important point is that the test isn't especially useful because it's just demonstrating that String.getBytes() can throw an exception, which it can obviously do. If you feel strongly about testing this functionality, I guess you could add a parameter for the encoding to f() and send a bad value into the test.
Also, you are causing the same problem for the caller of A.f() because A is final and f() is static.
This article might be useful in convincing your coworkers to be less dogmatic about 100% code coverage: How to fail with 100% test coverage.

From its documentation, JDave can't remove "final" modifiers from classes loaded by the bootstrap classloader. That includes all JRE classes (from java.lang, java.util, etc.).
A tool that does let you mock anything is JMockit.
With JMockit, your test can be written as:
import java.io.*;
import org.junit.*;
import mockit.*;
public final class ATest
{
#Test(expected = UnsupportedOperationException.class)
public void test() throws Exception
{
new Expectations()
{
#Mocked("getBytes")
String aString;
{
aString.getBytes(anyString);
result = new UnsupportedEncodingException("Parsing error.");
}
};
A.f("test");
}
}
assuming that the complete "A" class is:
import java.io.*;
public final class A
{
public static String f(String str)
{
try {
return new String(str.getBytes("UTF-8"));
}
catch (UnsupportedEncodingException e) {
throw new UnsupportedOperationException(e);
}
}
}
I actually executed this test in my machine. (Notice I wrapped the original checked exception in a runtime exception.)
I used partial mocking through #Mocked("getBytes") to prevent JMockit from mocking everything in the java.lang.String class (just imagine what that could cause).
Now, this test really is unnecessary, because "UTF-8" is a standard charset, required to be supported in all JREs. Therefore, in a production environment the catch block will never be executed.
The "need" or desire to cover the catch block is still valid, though. So, how to get rid of the test without reducing the coverage percentage? Here is my idea: insert a line with assert false; as the first statement inside the catch block, and have the Code Coverage tool ignore the whole catch block when reporting coverage measures. This is one of my "TODO items" for JMockit Coverage. 8^)

Mockito can't mock final classes. JMock, combined with a library from JDave can. Here are instructions.
JMock doesn't do anything special for final classes other than rely on the JDave library to unfinalize everything in the JVM, so you could experiment with using JDave's unfinalizer and see if Mockito will then mock it.

You can also use PowerMock's Mockito extension to mock final classes/methods even in system classes such as String. However I would also advice against mocking getBytes in this case and rather try to setup your expectation so that a real is String populated with the expected data is used instead.

You will be testing code that can never be executed. UTF-8 support is required to be in every Java VM, see http://java.sun.com/javase/6/docs/api/java/nio/charset/Charset.html

It is a project requirement that the unit tests coverage percentage must but higher than a given value. To achieve such percentage of coverage the tests must cover the catch block relative to the UnsupportedEncodingException.
What is that given coverage target? Some people would say that shooting for 100% coverage isn't always a good idea.
Besides, that's no way to test whether or not a catch block was exercised. The right way is to write a method that causes the exception to be thrown and make observation of the exception being thrown the success criterion. You do this with JUnit's #Test annotation by adding the "expected" value:
#Test(expected=IndexOutOfBoundsException.class) public void outOfBounds() {
new ArrayList<Object>().get(1);
}

Have you tried passing an invalid charsetName to getBytes(String)?
You could implement a helper method to get the charsetName, and override that method within your test to a nonsense value.

Perhaps A.f(String) should be A.f(CharSequence) instead. You can mock a CharSequence.

If you can use JMockit, look at Rogério answer.
If and only if your goal is to get code coverage but not actually simulate what missing UTF-8 would look like at runtime you can do the following (and that you can't or don't want to use JMockit):
public static String f(String str){
return f(str, "UTF-8");
}
// package private for example
static String f(String str, String charsetName){
try {
return new String(str.getBytes(charsetName));
} catch (UnsupportedEncodingException e) {
throw new IllegalArgumentException("Unsupported encoding: " + charsetName, e);
}
}
public class TestA {
#Test(expected=IllegalArgumentException.class)
public void testInvalid(){
A.f(str, "This is not the encoding you are looking for!");
}
#Test
public void testNormal(){
// TODO do the normal tests with the method taking only 1 parameter
}
}

You can change your method to take the interface CharSequence:
public final class A {
public static String f(CharSequence str){
try {
return new String(str.getBytes("UTF-8"));
} catch (UnsupportedEncodingException e) {
// This is the catch block that I want to exercise.
...
}
}
}
That way, you can still pass in String, but you can mock any way you like.

instead of mocking string inject string value at setup method as below
public void setup() throws IllegalAccessException {
FieldUtils.writeField(yourTestClass, "stringVariableName", "value", true);
}

If you have a block of code that can never actually be run, and a managerial requirement to have 100% test coverage, then something's going to have to change.
What you could do is make the character encoding a member variable, and add a package-private constructor to your class that lets you pass it in. In your unit test, you could call the new constructor, with a nonsense value for the character encoding.