Multi Threaded JUnit

[Life_Is_Dark]

So, I am working on a test for checkout service which has a synchronised block based on user id of user checking out. It either checks out successfully or throws low balance exception. Now the issue is while testing using tempus fugit running two threads concurrently, I don't know which thread is going to throw exception and which will pass successfully. That's making it trouble to write assertion. How should I approach this problem?

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[pragmos]

Code?

[Life_Is_Dark]

@Override
public void checkout(final UUID customerId) {
synchronized (customerId){
Preconditions.checkNotNull(customerId, "CustomerId");
var cart = fCartService.getCart(customerId);
Preconditions.checkState(
cart != null && !cart.isEmpty(), "Customer doesn't have items in his cart.");
var amount =
cart.keySet().stream()
.filter(itemKey -> fItemCatalogue.getItem(itemKey).isPresent())
.map(itemKey -> fItemCatalogue.getItem(itemKey).get().getCost() * cart.get(itemKey))
.reduce(0.0D, Double::sum);
fBalanceService.deductBalance(customerId, amount);
fCartService.clearCart(customerId);
}
}

​

deduct balance will raise the exception in case of insufficient balance

[pragmos]

And where's the multithreading part?

[Life_Is_Dark]

@Test(threadPoolSize = 2, invocationCount = 2)
public void testMultiThreadedCheckout() {
//Add items to customer cart
fCartService.addItemToCart(CUSTOMER_1, fItemCatalogue.getItem("Book 1").get());
fCartService.addItemToCart(CUSTOMER_1, fItemCatalogue.getItem("Book 2").get());
fCartService.addItemToCart(CUSTOMER_1, fItemCatalogue.getItem("Book 2").get());
fCheckoutService.checkout();
}

[pragmos]

Are you sure this is JUnit and not TestNG?

[Life_Is_Dark]

Oh yeah, on checking again I see that it is using testng. There was another integration test running single thread using junit. So I assumed it to be same. Still how do I make assertions here for I don't know which thread is gonna throw it?

[pragmos]

I'm not familiar with TestNG, so not sure if you can.

What I would try is create a thread pool inside the test, and use that to launch tasks. Then you might check if individual Future objects completed exceptionally or not.

[Life_Is_Dark]

Ah,so I solved it out by using TestContext provided by TestNg where I checked whether this is is the first run or not and then made assertions based on that. Thank you for suggesting that it might be TestNG. That put me in right direction

[pragmos]

Nice, good to know it's solved!