Develop Reference

If you want to use assertThrows while testing, should you do that with stubs or mocks?

I have this Method that throws an IllegalArgumentException when somebody tries to call it with value 0.
I want to write several stub and mock tests - for example - for the method getFrequentRenterPoints.
I coudn't figure out any "when" or "verify" statements which are used in mocks so I mixed parts of mocks and parts of stubs together and came up with this:
#Test
public void methodGetFrequentRenterPointsShouldThrowIllegalArgumentException() {
//given
Movie movieMock = mock(Movie.class);
//when
movieMock.getFrequentRenterPoints(0);
//then
assertThrows(IllegalArgumentException.class, () -> {
movieMock.getFrequentRenterPoints(0);
});
}
Is it okay to have in a class with other Mocks, or if I want to use assertThrows should I change this into a stub? Or can I use assertThrows with mocks?

The answer from Benjamin Eckardt is correct.
But I try to approach this question from another point of view: when to use mocking? This is one of my favourite answers to that question.
So in practise:
Say your code is like (just guessing all the business objects & names...):
List<RenterPoints> getFrequentRenterPoints(int renterId) {
if(p <= 0) {
throw new IllegalArgumentException();
}
// this is just the rest of code in which your test does not enter because
// of thrown exception
return somethingToReturn();
}
For this you do not need and you should not want to mock anything here.
But when things get more complicated like your method would be like:
List<RenterPoints> getFrequentRenterPoints(int renterId) {
if(p <= 0) {
throw new IllegalArgumentException();
}
// What is this?
// It is injected in the Movie - say - like
//
// #Resource
// private RenterPointService renterPointService;
List<RenterPoints> unfiltered = renterPointService.getRenterPoints(renterId);
return filterToFrequent(unfiltered);
}
Now if you test renterId >= 1 what about this renterPointService how do you instantiate it to not get NPE? Say if it is injected and requires to pull up heavy framework for testing or it requires very heavy construction or so? You do not, you mock it.
You are testing the class Movie not the class RenterPointService so you should not bother to think how RenterPointService works but what it returns when used in the class Movie. Still: you do not mock the class Movie which you are testing.
Assuming using you are using Mockito and using annotations the mocking would be then done in your test class like:
#Mock
private RenterPointService renterPointService;
#InjectMocks
private Movie movie;
Then you would do mocking of methods for renterPointService like:
when(renterPointService.getRenterPoints(anyInt))
.thenReturn(someListContaineingMockRenterPointsForThisTest);

Usually you expect the tested production method to throw and not the mock or stub. I drafted it by using new Movie().
Furthermore in that case it does not really make sense to separate the calls into when and then because if movieMock.getFrequentRenterPoints(0); throws, assertThrows(...) will never be executed.
To apply the given/when/then structure with the assertThrows API you could extract the passed lambda in some way, but I personally don't see much benefit in it.
#Test
public void methodGetFrequentRenterPointsShouldThrowIllegalArgumentException() {
// given
Movie movieMock = new Movie();
// when/then
assertThrows(IllegalArgumentException.class, () -> {
movieMock.getFrequentRenterPoints(0);
});
}

Simple Unit test with Mocks keeps failing; mock object not being passed to class?

I have a simple Unit Test that is failing. Hopefully I can explain this in simple terms as I've been looking at it for hours and I see what the issue is, but I am not too familiar the underlying theory behind Mocks so I am a bit confused and cannot fix it. I will summarize the issue very quickly and then paste the code below.
Basically, in my test method called getAllValidModelsTest(), it uses a for loop to iterate thru enum values of object type DeviceModel. There are only 5: [EX3400_24P, EX4300_32F, EX4300_48MP, SRX_345, FAUX].
So inside the for loop, before the Assert statement (Junit), it makes a static method call to getDevice(deviceId) and it should from there return a Device object. The first line under the for loop in the getAllValidModelsTest() mocks the elementMock object to return the current model that is being iterated over in the DeviceModels[] array that was returned from the .values() call on the enums DeviceModel class.
So my issue is, when it jumps in the 2nd iteration in my for loop (counting from 1), the Assert fails , because the 0th element in the DeviceModel[] array is obviously EX4300_32F, but in the #Before setUp annotation it is being mocked to return EX3400_24P. But the weird thing is, under the for loop inside the getAllValidModelsTest() method, it is being overridden/mocked again to return to the current model that is being iterated through when .getModel is called on the elementMock object, so it should be returning the SAME value...
This is how the class SwitchDeviceFactoryTest.java is constructed (the class with the Unit Test):
#PowerMockIgnore({"javax.net.ssl.*"})
#RunWith(PowerMockRunner.class)
#PrepareForTest({DataGatewayFactory.class, SwitchConfig.class, RouterConfig.class})
public class SwitchDeviceFactoryTest {
String deviceId = "testdevice";
String ip = "1.1.1.1";
DataGateway dbMock = Mockito.mock(DataGateway.class);
SwitchConfig swConfigMock = PowerMockito.mock(SwitchConfig.class);
RouterConfig routerConfigMock = PowerMockito.mock(RouterConfig.class);
TransportDeviceSecretsInfo secrets = new TransportDeviceSecretsInfo();
TransportDeviceSecretsData secretsData = new TransportDeviceSecretsData("root","rootPw", "sshUser", "sshPass", "snmpAuthPass", "snmpPrivPass");
IElement elementMock = Mockito.mock(IElement.class);
ITransportDeviceSecretsCrud transportDeviceSecretsCrud = mock(ITransportDeviceSecretsCrud.class);
ISwitchConfigCrud switchConfigCrud = mock(ISwitchConfigCrud.class);
IRouterConfigCrud routerConfigCrud = mock(IRouterConfigCrud.class);
IElementCrud elementCrud = mock(IElementCrud.class);
This is my setUp method that runs before the test. The only variables that should be of importance are the elementMock object, specifically the one being mocked to return the EX3400_24P object:
#Before
public void setup() throws Exception {
secrets.setSecretsData(secretsData);
PowerMockito.mockStatic(DataGatewayFactory.class);
Mockito.when(DataGatewayFactory.getInstance()).thenReturn(dbMock);
Mockito.when(dbMock.getTransportDeviceSecretsCrud()).thenReturn(transportDeviceSecretsCrud);
Mockito.when(transportDeviceSecretsCrud.getServerSecretsInfo(anyString())).thenReturn(Optional.of(secrets));
Mockito.when(transportDeviceSecretsCrud.getReportedSecretsInfo(anyString())).thenReturn(Optional.of(secrets));
when(dbMock.getElementCrud()).thenReturn(elementCrud);
doReturn(Optional.of(elementMock)).when(elementCrud).getById(anyString());
Mockito.when(elementMock.getModel()).thenReturn(DeviceModel.EX3400_24P.getModel());
Mockito.when(elementMock.getType()).thenReturn(ElementType.SWITCH);
Mockito.when(dbMock.getSwitchConfigCrud()).thenReturn(switchConfigCrud);
Mockito.when(switchConfigCrud.get(anyString())).thenReturn(Optional.of(swConfigMock));
Mockito.when(swConfigMock.getIp()).thenReturn(ip);
Mockito.when(dbMock.getRouterConfigCrud()).thenReturn(routerConfigCrud);
Mockito.when(routerConfigCrud.get(anyString())).thenReturn(Optional.of(routerConfigMock));
Mockito.when(routerConfigMock.getIp()).thenReturn(ip);
And the test method:
#Test
public void getAllValidModelsTest() throws Exception {
for (DeviceModel model: DeviceModel.values()) {
when(elementMock.getModel()).thenReturn(model.getModel());
if (model == DeviceModel.SRX_345)
when(elementMock.getType()).thenReturn(ElementType.ROUTER);
else
when(elementMock.getType()).thenReturn(ElementType.SWITCH);
Device device = DeviceFactory.getDevice(deviceId);
assertEquals(model, device.getModel());
}
}
The thing that doesn't make sense, is I was refactoring code, and only changed 2 lines (the elementCrud and elementMock .doReturn and .when calls) and it works perfectly fine on the develop branch.
When I debug, I can see that on the 2nd iteration of the for loop, .getModel returns EX3400_24P object inside the static getDevice method, when it should be returning model.getModel() , which would be the 2nd object being iterated on in the .values() enum array of DeviceModels... so it should be EX4300_32F.
On the develop branch, this works perfectly.... It's as if the Mockito mock object forgets what it's suppose to do when it jumps inside the DeviceFactory class inside the getDevice method once its called in my getAllValidModelsTest() method (i.e. Device device = DeviceFactory.getDevice(deviceId);)
Here is the .getDevice method from the DeviceFactory class:
public static Device getDevice(String serialNumber) throws Exception {
IElement element = dataGateway.getElementCrud().getById(serialNumber).get();
DeviceModel model = DeviceModel.valueOfLabel(element.getModel()); // right here is where it returns the wrong model... it returns EX3400_24P on the 2nd iteration
log.info("Found device {} in database", serialNumber);
if (serialNumber.startsWith(FakeDevicePrefix.ATGTEST.toString()) || serialNumber.startsWith(FakeDevicePrefix.FAKE.toString())) {
log.info("Detected FAKE/ATG serial number. Using FAUX device.");
model = DeviceModel.FAUX;
}
switch (element.getType()) {
case SWITCH:
SwitchConfig config = dataGateway.getSwitchConfigCrud().get(serialNumber).get();
return getDevice(serialNumber, config.getIp(), model);
case ROUTER:
RouterConfig rconfig = dataGateway.getRouterConfigCrud().get(serialNumber).get();
return getDevice(serialNumber, rconfig.getIp(), DeviceModel.SRX_345);
case PTP:
default:
log.warn("Unsupported device type {}", element.getType().toString());
throw new Exception("Unsupported device type " + element.getType().toString());
}
}
I did indeed comment out/remove the piece of code that mocks it to return EX3400_24P in the setUp() method with #Before annotation , but the tests fails with a NULL POINTER EXCEPTION at this point.
How does the .getModel method know to return what I mocked it to return in the previous class (SwitchDeviceFactoryTest.java) before it jumps into the DeviceFactory.java class? How does it remember that if I'm not passing it in as a variable into the getDevice() method?
Do I need to use PowerMock or something because this is a static method? How does this change anything?
Please help!

Mockito/Realm (when-then): how to pass arguments from method to its submethod

Trying to unit test a project that uses Realm. I stubbed realm methods to just test my own code and found a problem with RealmQuery. I want to test whether an object is (1) added to the Realm db; (2) can be retrieved; (3) if that object's set attribute matches what I expect. Here are parts of my setup() and Test.
How I stub a realm database (someList is global & List<>) in setup()
SomeRealmObject some1;
some1.setId(1);
some1.setName("some1");
SomeRealmObject some2;
some2.setId(2);
some2.setName("some2");
someList = new ArrayList<SomeRealmObject>();
someList.add(some1);
someList.add(some2);
How I stub copying to Realm (add function) in setup()
when(mockRealm.copyToRealm).then(new Answer() {
#Override
public Object answer(InvocationOnMock invocation) throws Throwable {
Object[] args = invocation.getArguments();
SomeRealmObject some = (SomeRealmObject) args[0];
userList.add(user);
return user;
}
});
How I stub RealmQuery (search function) in setup()
RealmQuery someRealmQuery = someRealmQuery(); //followed mockito example on github
when(mockRealm.where(SomeRealmObject.class)).thenReturn(someRealmQuery);
when(realmQuery.equalsTo(anyString, anyInt).thenReturn(someRealmQuery);
when(realmQuery.findFirst()).then(findFirstAnswer);
Problem starts here. I need realmQuery.equalsTo(...) to pass its arguments to the next method in the chain. I think it necessary (but I may be wrong) because I should test two methods that follow: findFirst() and findAll(). Any Ideas?
How I stub findFirst() in setup()
Answer findFirstAnswer = new Answer(){
#Override
public Object answer(InvocationOnMock invocation) throws Throwable {
Object[] args = invocation.getArguments();
String key = args[0].toString(); //Let's just use an Id search for
int id = (int) args[1]; //an example.
for(int count = 0; someList.get(count) != null; count++){
if(someList.get(count).getId == id){
return someList.get(count);
}
return null; //test will fail, someRealmObject not found
}
}
How I unit test my createSomeObject (e.g. createAccount)
#Test
public void create_someObj_test() {
String expectedReturnedName = "someName";
String actualReturnedName;
SomeRepositoryImpl manager; //Class with business logic (mvp pattern)
SomeRepositoryImpl.initialize();
manager = someRepositoryImpl.getInstance();
SomeRealmObject some = new SomeRealmObject();
some.setID(6);
some.setName(expectedReturnedName);
//mock adding user to realm, should actually add it to a list
mockRealm.beginTransaction();
mockRealm.copyToRealm(some);
mockRealm.commitTransaction();
actualReturnedName = mockRealm.where(SomeRealmObject.class).equalTo("id", some.getId()).findFirst().getName().toString();
//PASS if object exists and name matches
//FAIL if name does not match
//FAIL if nullPointerException because no match/object not found
assertEquals(expectedReturnedName, actualReturnedName );
}

This is not a direct answer to your question. A direct answer would involve a discussion of what findFirstAnswer is and what its name property contains.
Instead, though, I would ask: "what are you trying to test"? This is not quite a test of the Realm DB library (a good thing). It looks to me almost like a test of Mockito! If the test succeeds, you will know that Mockito Mocks can return an object with a certain name.
It is common practice to wrap a data layer in a very thin API, something like the Data Access Objects popular with Spring and the like. If you can mock the data API, you can test the heck out of your business layer. If your data API needs testing, you can also test things like "does this API call get translated into the proper query?" or "does the API crash if the result is empty?".
Sorry for the oblique answer but I think if you revisit the question of what you are trying to test, this entire problem might evaporate.

Test method that returns void

I have a void method and I want to test it. How do I do that?
Here's the method:
public void updateCustomerTagCount() {
List<String> fileList = ImportTagJob.fetchData();
try {
for (String tag : fileList) {
Long tagNo = Long.parseLong(tag);
Customer customer = DatabaseInterface.getCustomer(tagNo);
customer.incrementNoOfTimesRecycled();
DatabaseInterface.UpdateCustomer(customer);
}
} catch(IllegalArgumentException ex) {
ex.printStackTrace();
}
}

when the method returns void, you can't test the method output. Instead, you must test what are the expected consequences of that method. For example:
public class Echo {
String x;
public static void main(String[] args){
testVoidMethod();
}
private static void testVoidMethod() {
Echo e = new Echo();
//x == null
e.voidMethod("xyz");
System.out.println("xyz".equals(e.x)); //true expected
}
private void voidMethod(String s) {
x = s;
}
}

It might not be always true, but basic concept of unit test is to check if function works as expected and properly handling errors when unexpected parameters/situation is given.
So basically unit test is against the functions that takes input parameters and return some output so we can write those unit test.
The code like yours, however, includes some other dependency (database call) and that's something you can't execute unless you write integration-test code or real database connection related one and actually that's not recommended for unit test.
So what you need to do might be introducing unit test framework, especially Mockto/Powermock or some other stuff that provides object mocking feature. With those test framework, you can simulate database operation or other function call that is going to be happening outside of your test unit code.
Also, about how do I test void function, there is nothing you can with Assert feature to compare output since it returns nothing as you mentioned.
But still, there is a way for unit test.
Just call updateCustomerTagCount() to make sure function works. Even with just calling the function, those unit test can raise your unit test coverage.
Of course for your case, you need to mock
ImportTagJob.fetchData();
and
DatabaseInterface.getCustomer(tagNo);
and have to.
Let mocked
ImportTagJob.fetchData();
throw empty list as well as non-empty list and check if your code works as you expected. Add exception handling if necessary. In your code, there are two condition depends on whether fieList are null or non-null, you need to test it.
Also, mock those objects and let them throw IllegalArgumentException where you expect it to be thrown, and write an unit test if the function throws a exception. In Junit, it should be like
#Test(expected = IllegalArgumentException.class)
public void updateCustomerTagCountTest(){
// mock the objects
xxxxx.updateCustomerTagCount();
}
That way, you can ensure that function will throw exception properly when it has to.

How do I test a very simple void method in jUnit?

I know there are several question about void-method Unit-Testing, but my question is different.
I'm learning java, so my boss give me some tasks with different requirements on my tasks.
In my actual task, there is a requirement which says, the jUnit test must cover >60%. So I need to test a very simple method to reach this 60%. The method is the following:
public void updateGreen() {
// delete this outprint if the Power Manager works
System.out.println(onCommand + "-green");
// p = Runtime.getRuntime().exec(command + "-green");
// wait until the command is finished
// p.waitFor();
}
Because of intern problems, I can't execute the command with the Runtime task. So there is only a System.out in this method.
I've multiple methods like that, so tests for this method will cover over 10% of my whole code.
Is it useful to test such a method? When yes, how?

If there is a lot of such methods, the thing which you might want to test here is that updateScreen() uses the right string, "some-command-green" and that the System.out is being invoked. In order to do this you might want to extract System.out into an object field and mock it (i.e. with Mockito's spy()) to test the string that was provided to println.
I.e.
class MyClass{
PrintStream out = System.out;
public void updateGreen() { ... }
}
In test:
#Test
public void testUpdate(){
MyClass myClass = new MyClass();
myClass.out = Mockito.spy(new PrintStream(...));
// mock a call with an expected input
doNothing().when(myClass.out).println("expected command");
myClass.updateGreen();
// test that there was a call
Mockito.verify(myClass.out, Mockito.times(1)).println("expected command");
}

You could return true if the method ran successfully and false otherwise. It would be easy to test for this.
You could also test the output of this method, as described here:
Should we unit test console outputs?
But in my experience, it is much better to have methods return an optimistic or pessimistic value (true/false, 1/0/-1 etc) to indicate their status.
You can also write a getter method for the onCommand flag:
public string getFlag(){
// some logic here
return "green";
// otherwise default to no flags
return "";
}

You could test that onCommand + "-green" has been written to System.out by using the System Rules library.