class A {
public B getB(){
// somehow get argType1 and argType2
return new B(argType1, argType2);
}
}
class B{
public B(Type1 t1, Type2 t2){
// something
}
}
I want to Test A, and verify that constructor of B is getting called for expected values of argType1 and argType2.
How can i do this using PowerMockito?
Is there a way to pass argumentCaptor like this:
whenNew(B.class).withArguments(argType1Captor, argType2Captor).thenReturn(somemock);
if this do this, argType1Captor gets both the values
I solved it by doing this
PowerMockito,verifyNew(B.class).withArgument(expectedArgType1, expectedArgType2)
Dhrumil Upadhyaya, your answer (admittedly the only one offered) doesn't solve the question you asked! I think you might want to do something like:
public class MyTest {
private ArgType argument;
#Before
public void setUp() throws Exception {
MyClass c = mock(MyClass.class);
whenNew(MyClass.class).withAnyArguments()
.then((Answer<MyClass>) invocationOnMock -> {
argument = (ArgType) invocationOnMock.getArguments()[0];
return c;
}
);
}
}
It's not an elegant solution but it will capture the argument(s) passed to the constructor. The advantage over your solution is that if argument is a DTO then you can inspect it to see if it contains the values you were expecting.
Related
I would like to ask for a help and suggestions what is a correct approach in my case (probably its easy but I'm just starting with JUnit). Here is a part of my code
public boolean arrayListEmpty()
{
if(numericalSequence.isEmpty() == true)
return true;
else
return false;
}
This is a public method from model which I suppose i should test, it's just returning true if my numericalsequence is empty as you can see. I cant check it directly invoking numericalSequence.isEmpty (in controller where I need it) because it is private.
So obvious thing is to check
assertEquals(true, test.arrayListEmpty());
So my question is about suggestions what other asserts should I use/what cases should I predict which can come out. Should I in Test method fill numericalSequence with some values and assert it also? (for me its not necessary because any value inserted into sequence = not null but maybe it is not so easy)
First of all, welcome to Stack Overflow!
Looking at your question, it sounds like you're new to unit-testing (correct me if I'm wrong). So, I'll break my answers in to two sections; (1) answering your question, and (2) to give a general direction of how to write good tests and testable classes.
1. Answering your question
There are a couple more use cases you can think of here:
What happens if numericalSequence is null?
What if numericalSequence has 1 element?
What if numericalSequence has a null element?
Some of the cases above may not be possible depending on how your class is set up, but it's a test worth having so that any changes to the class that violates the "previously agreed behavior" of one of these test cases would fail.
2. Writing good tests
There are no strict guidelines on what to do in order to write good tests, however, if you structure your code to be testable, you'll find that writing good tests becomes easier, and would be less of chore. Allow me to explain.
NOTE: This is not a comprehensive guide, but is meant to start your journey in to the path of how to write better code, and better tests
So assume a class that needs to be tested is written like this:
class MyClass {
// NOTE: This is not `final`
private List<Integer> numericalSequence;
public MyClass() {
this.numericalSequence = new ArrayList<>();
}
public void doSomething(Integer x) {
if (x < 0) {
numericalSequence = new ArrayList<>();
} else {
numericalSequence.add(2 * x);
}
}
public boolean arrayListEmpty() {
// NOTE: Your sample code can be reduced to this one-liner
return numericalSequence.isEmpty();
}
}
Here are some of the flaws in the above code:
doSomething method allows nullable (boxed integer) values and so can cause NullPointerException in the first if statement.
The numericalSequence member is not final and hence the code that sets it to null is valid inside the doSomething method
The arrayListIsEmpty method does not check if numericalSequence is null
If I want to test how arrayListIsEmpty behaves when numericalSequence is null, or has null elements, it is hard to do so, unless you know how to get the class to that state.
If the class was re-written to the following:
class MyClass {
private final List<Integer> numericalSequence;
public MyClass() {
this(new ArrayList<>());
}
// Should be made public only if the classes that use this one needs to
// initialize this instance with the sequence. Make this package-private
// otherwise.
public MyClass(List<Integer> sequence) {
this.numericalSequence = sequence;
}
public void doSomething(int x) {
if (x < 0) {
// COMPILE ERROR: Cannot assign to a final member
// numericalSequence = new ArrayList<>();
numericalSequence.clear();
} else {
numericalSequence.add(2 * x);
}
}
public boolean arrayListEmpty() {
return numericalSequence == null || numericalSequence.isEmpty();
}
}
A few things to note about the above structure:
There are two constructors; the default invokes the one that takes a list of integers as the sequence, so that it reuses any logic that both would need to share. There are no logic in this example, but hopefully you'll come across one soon.
The doSomething() method doesn't accept Integer value, but int value that makes sure that x is never null (Java numerical primitive types cannot be null). This also means, numericalSequence cannot contain null values through doSomething().
Since numericalSequence can be initialized from outside of this class, the arrayListEmpty() method makes sure to check that numericalSequence is either null is truly empty.
Now you can write test cases like so:
#Test
public void arrayListEmpty_WhenListIsNull() {
MyClass test = MyClass(null);
assertTrue(test.arrayListEmpty());
}
#Test
public void arrayListEmpty_WhenListIsEmpty() {
MyClass test = MyClass();
assertTrue(test.arrayListEmpty());
}
#Test
public void arrayListEmpty_WhenListHasOnlyOneNonNullElement() {
List<Integer> sequence = new ArrayList<>();
sequence.add(0);
MyClass test = new MyClass(sequence);
assertFalse(test.arrayListEmpty());
}
#Test
public void arrayListEmpty_WhenListHasOnlyOneNullElement() {
List<Integer> sequence = new ArrayList<>();
sequence.add(null);
MyClass test = new MyClass(sequence);
assertFalse(test.arrayListEmpty());
}
Since doSomething() adds/clears the sequence, when writing tests for doSomething() make sure the call and verify the state of the class by checking the return value of arrayListEmpty().
For example:
#Test
public void doSomething_WhenInputLessThanZero() {
List<Integer> sequence = new ArrayList<>();
sequence.add(0);
MyClass test = new MyClass(sequence);
test.doSomething(-1);
assertTrue(test.arrayListEmpty());
}
My intention was to show a couple of things:
Structure your tests cases to be small and concise
Design your class to be easily testable
Hope this helps.
how to mock an instance method invocation from static method while writing junit for static method?I'm writing tests for existing code.
class A
{
public static D methodX()
{
B b = new B();
C c = b.doSomething();
}
}
class B
{
public C doSomething()
{
return C;
}
}
class Atest
{
#Test
public void testMethodX()
{
B b =Mockito.mock(B.class);
Mockito.when(b.doSomething()).thenReturn(new C());
A.methodX();
// some assertions
}
}
By your tag selection you already know that you need to go for PowerMockito.
In order to inject a mocked version of B class i would do the following:
A class
class A
{
public static D methodX()
{
B b = getBInstance();
C c = b.doSomething();
}
static B getBInstance(){
return new B();
}
}
Test Class
#RunWith(PowerMockRunner.class)
#PrepareForTest(A.class)
class Atest
{
#Test
public void testMethodX()
{
B b =Mockito.mock(B.class);
PowerMockito.stub(PowerMockito.method(A.class, "getBInstance")).toReturn(b);
Mockito.when(b.doSomething()).thenReturn(new C());
A.methodX();
// some assertions
}
}
Thanks to PowerMockito.stub(PowerMockito.method call you will just mock the getBInstance static method and in the end call the real A.methodX implementation.
Another completely different approach: do not write un-testable code. static is an abnormality within good OO designs; to the first step is to simply not write static methods.
And when you have good reasons to still do so; then write them in a way that allows you reasonable unit-test them.
Yes, it is possible to turn to PowerMock(ito) to get this solved, but the more sane approach is to simple fix your production design.
The PowerMock(ito) frameworks come at certain cost; and can easily be avoided.
Thus, my answer: learn how to create testable code; and simply forget about PowerMock (you can start by watching these videos).
Would appreciate some help with hamcrest and junit matchers... :)
I'm using junit-4.11.jar and hamcrest-core-1.3.jar on Eclipse Kepler with sun's jdk 1.6.0_30.
I have a class that holds an instance of any unknown type like so:
class UnknownClassHolder {
private Class<?> clazz;
public Class<?> getClazz() {
return clazz;
}
public void setClazz(Class<?> clazz) {
this.clazz = clazz;
}
}
clazz can be any class.
I want to my junit test to be something like this:
class UnknownClassHolderTest {
#Test
public void test() {
ArrayList<UnknownClassHolder> list = new ArrayList<UnknownClassHolder>();
UnknownClassHolder x = new UnknownClassHolder();
//lets add an Integer
x.setClazz(Integer.class);
list.add(x);
UnknownClassHolder y = new UnknownClassHolder();
//lets add a vector
y.setClazz(Vector.class);
list.add(y);
//now check that we added an Integer or a Vector using assertThat
for (UnknownClassHolder u: list) {
assertThat(u.getClazz(), anyOf(isA(Integer.class), isA(Vector.class))));
}
}
}
Junit's assertThat doesn't like this. It doesn't compile due to Integer & Vector Types not being related to each other via sub/super classes:
The method assertThat(T, Matcher<? super T>) in the type Assert is not applicable for the arguments (Class<capture#1-of ?>, AnyOf<Vector>)
Is there a more succinct way to do this other than:
assertThat(u.getClazz().getName(), either(is(Integer.class.getName())).or(is(Vector.class.getName())));
Is there a particular reason for using Matcher<? super T> rather than Matcher<?> in the org.hamcrest.MatcherAssert.assertThat(...) method?
Thanks.
First, you should be using is instead of isA since you're asserting that one class equals another. isA is for testing that an object is an instance of some class. Second, the only thing I can make work is forcing the compiler to see these as raw Objects.
assertThat(u.getClazz(), anyOf(is((Object) Integer.class), is((Object) Vector.class)));
all of the samples i've seen online with regard to custom parametersuppliers have something like:
List<PotentialAssignment> list = new ArrayList<PotentialAssignment>();
list.add(PotentialAssignment.forValue("teams", "giants"));
list.add(PotentialAssignment.forValue("teams", "jets"));
list.add(PotentialAssignment.forValue("teams", "niners"));
return list;
now, the question i have is: what does the first argument to PotentialAssignment.forValue(arg1, arg2) do? Nothing i've seen online has explained the significance of it.
thanks
The first parameter of PotentialAssignment.forValue is the "name" of the value. It is not used, if your #Theory method passes, but if it fails, it is used to assemble the error message. Here is an example:
#RunWith(Theories.class)
public class CustomParameterSupplierTest {
#Retention(RetentionPolicy.RUNTIME)
#Target(ElementType.PARAMETER)
#ParametersSuppliedBy(FooSupplier.class)
public #interface Foo {}
public static class FooSupplier extends ParameterSupplier {
#Override
public List<PotentialAssignment> getValueSources(ParameterSignature sig) {
return Arrays.asList(
PotentialAssignment.forValue("one", 1),
PotentialAssignment.forValue("two", 2)
);
}
}
#Theory
public void test(#Foo int foo) {
assertThat(foo, is(1));
}
}
If this test is executed with Junit 4.11 you will get the following error:
org.junit.experimental.theories.internal.ParameterizedAssertionError: test(two)
By the way, in the upcoming release JUnit 4.12 the error reporting is further improved and you will get the following error:
org.junit.experimental.theories.internal.ParameterizedAssertionError: test("2" <from two>)
All,
I am currently using JUnit 4 for writing test cases. I am fairly new to JUnit and finding it difficult to test my main class which takes arguments. I have specified the arguments to my JUnit test class by:
1 > Right click JUnit test class
2 > Goto Run As -> Run Configurations
3 > Select the Arguments tab and specify a value (I have entered an invalid argument i.e. the main class expects the command line argument to be converted to an int and I am passing a String value that cannot be converted to int)
However, the main class that I am testing, if the command line argument cannot be converted to a int, than I throw IllegalArgumentException. However, the JUnit does not show the testMain() method as Error or Failure. I don't think my setup is right for the JUnit class. Can anyone please guide me where I am going wrong
To test your class main method simply write something like:
#Test(expected = IllegalArgumentException.class)
public void testMainWithBadCommandLine()
{
YourClass.main(new String[] { "NaN" });
}
Change the main() method to something like this:
public static void main(String[] args)
{
MyClass myclass = new MyClass(args);
myclass.go();
}
Move the code that was in main() to the new method go(). Now, your test method can do this:
public void myClassTest()
{
String[] args = new String[]{"one", "two"}; //for example
MyClass classUnderTest = new MyClass(testArgs);
classUnderTest.go();
}
Firstly the arguments should be in the program arguments section. Normally the launching point of the application that's the main method doesn't need to be tested if you design the app to be testable.
Refactor the class
public static class ArgumentValidator
{
public static boolean nullOrEmpty(String [] args)
{
if(args == null || args.length == 0)
{
throw new IllegalArgumentException(msg);
}
//other methods like numeric validations
}
}
You can now easily test the nullOrEmpty method using junit like
#Test(expected = IllegalArgumentException.class)
public void testBadArgs()
{
ArgumentValidator.nullOrEmpty(null);
}
I think this is a better approach