I was writting JUnit test. I would like to know if the tests within a test class can run in parallel.
class TestMyClass {
#Test
public void test1() {
}
#Test
public void test2() {
}
}
Will Junit ever run test1() and test2() in parallel?
Consider TestNG if you are looking for Parallel tests execution.
Yes, you can. Take a look at this question for details on how to set that up. The correctness of your tests should not really on this behaviour though. Your tests should run correctly if they're run concurrently or not.
I cannot directly answer on whether jUnit will run them in parallel or not, but theoretically that shouldn't matter. The only thing you should keep in mind is the sequence of execution you can bet on, like
setup
execution of test
teardown
This should be enough, as each single test should be completely independent from each other. If your tests depend on the order they're executed or whether they run in parallel, then you probably have some wrong dependencies.
No, because a fixture is setUp before each test. Running test in parallel could change the fixture state. I guess you could write a test executor to run tests in parallel.
Related
I'm running my integration tests in parallel but I have one tests that counts the number of rows in one table but the number can vary depending on many tests have run before that tests runs.
Is there any mechanism in Spring or Junit that would allow me to make sure that when that tests runs that table is clean so that the count would always be 1?
Thanks
You can use BeforeEach annotation within Junit class:
#BeforeEach
void foo() {
clearDBrows();
}
void clearDBrows(){
//clear db rows
..
}
This is by considering, your other test's wont really care if db table rows get cleared before execution as #BeforeEach will get executed for every tests you run.
I have two FitNesse suits which are mutually exclusive and I want to run them in parallel.
As they are invoked from a junit test case, I have written the following piece of code:
#Test
public void executeFitnesseSuites() {
final Class<?>[] classes = { Suite1.class, Suite2.class };
final Result result = JUnitCore.runClasses(ParallelComputer.classes(), classes);
System.out.println(result);
}
#RunWith(FitNesseRunner.class)
#FitNesseRunner.Suite("Suite1")
#FitNesseRunner.FitnesseDir(".")
#FitNesseRunner.OutputDir("/tmp/fitnesse/")
public static class Suite1{
}
#RunWith(FitNesseRunner.class)
#FitNesseRunner.Suite("Suite2")
#FitNesseRunner.FitnesseDir(".")
#FitNesseRunner.OutputDir("/tmp/fitnesse/")
public static class Suite2{
}
In the earlier implementation, these were two independent classes and were being executed sequentially.
However, I am seeing a similar execution time for the above test.
Does this mean that FitNesse is not spinning up two slim server instances and executing these suites in parallel?
Unfortunately FitNesse itself is not thread safe, so one should not run two slim server instances in one JVM at the same time.
I'm not sure how jUnit behaves using the approach you use. Does it spin up two parallel JVMs, or just threads in the same JVM?
An approach I've used in the past to run two completely independent suites with jUnit is two have two separate classes (as you had before) and run these in parallel on separate JVMs using Maven's failsafe plugin. Failsafe (and surefire as well) offers a forkCount property to specify the number of processes to use (see http://maven.apache.org/surefire/maven-failsafe-plugin/examples/fork-options-and-parallel-execution.html for more details). Please note that you should NOT use the parallel property as that is within one JVM.
If you are running tests in parallel using FitNesse's jUnit runner you may also be interested in a tool I created to combine the HTML reports of such runs into a single report: HtmlReportIndexGenerator. This is part my fixtures jar, but also available as separate docker image: hsac/fitnesse-fixtures-combine.
Poorly written unit tests are generally affected by the parallelism in JUnit execution. Can setting the number of threads for JUnit helps?
I read it somewhere, but I'm not sure. Can someone tell how can we set it? And where?
By defaul jUnit executes #Test methods in 4 threads. Howerver you can increase that number by putting:
junit.jupiter.execution.parallel.config.fixed.parallelism={numberOfThreads}
into:
src/main/resources/junit-platform.properties
Suppose I want to manually run from my IDE (Intellij IDEA, or eclipse) 4000 JUnit tests; the first 1000 tests run pretty smoothly (say they take 3 minutes all 1000) but the test 1001 takes alone over 30 minutes.
Is there a way I can skip the test 1001 (while it's still running) and to let the test 1002 (and the others) keep going. I do not want to #Ignore the test 1001 and rerun the suite because I already have the answer for tests 1-1000; also I do not want to select tests 1001-4000 because it takes too much time.
I would some kind of button - Skip Current Test - which can be pressed when the test is running.
In case such feature does not exist, an enhancement for it needs to be done by the IDE developers or by JUnit developers?
This is actually pretty simple with JUnit 4 using Assume. Assume is a helper class like Assert. The difference is that Assert will make the test fail while Assume will skip it.
The common use case is Assume.assumeTrue( isWindows() ) for tests that only work on, say, a Windows file system.
So what you can do is define a system property skipSlowTests and add
Assume.assumeTrue( Boolean.getBoolean("skipSlowTests") )
at the beginning of slow tests that you usually want to skip. Create an Eclipse launch configuration which defines the property to true and you have a convenient way to switch between the two.
If you want to run a slow test, select the method in Eclipse (or the whole class) and use "Run as JUnit Test" from the context menu. Since the property is false by default, the tests will be run.
No, you cannot skip tests if they are already running.
What I suggest you do is use Categories to separate your slow tests from the rest of your tests.
For example:
public interface SlowTests {
}
public class MyTest {
#Test
public void test1{
}
#Category(SlowTests.class)
#Test
public void test1001{
// this is a slow test
}
}
Create a test suite for the fast tests.
#RunWith(Categories.class)
#ExcludeCategory(SlowTests.class)
#SuiteClasses(MyTest.class)
public class FastTestSuite {
}
Now execute the FastTestSuite if you don't want to run the slow tests (e.g. test1001). Execute MyTest as normal if you want to run all the tests.
What you're asking for is to stop executing your code while it is in mid test. You can't stop executing a current test without having hooks in your code to allow it. Your best solution is to use Categories as others have suggested.
Basically, JUnit executes all of the #Before methods (including #Rules), then your #Test method, then the #After methods (again, including #Rules). Even assuming that JUnit had a mechanism for stopping execution of it's bits of the code (which it doesn't), most of the time is spent in your code. So to 'skip' a test which has already started requires you to modify your test code (and potentially the code that it's testing) in order that you can cleanly stop it. Cleanly stopping an executing thread is a question in itself [*].
So what are your options?
Run the tests in parallel, then you don't have to wait as long for the tests to finish. This may work, but parallelizing the tests may well be a lot of work.
Stop execution of the tests, and fix the one that's you're working on. Most IDEs have an option to kill the JVM in which the tests are running. This is definitely the easiest option.
Implement your own test runner, which runs the test in a separate thread. This test runner then either waits for the thread to finish executing, or checks a flag somewhere which would be a signal for it to stop. This sounds complicated, because you need t manage your threads but also to set the flag in a running jvm. Maybe creating a file somewhere? This runner would then fail the currently running test, and you could move on to the next. Please note that 'stopping' a test midway may leave stuff in an inconsistent state, or you may end up executing stuff in parallel.
There are parallel JUnit runners out there, and I don't think you're going to get much help from IDE developers (at least in the short term). Also, look at TestNG, which allows stuff to be run in parallel.
For using categories, one solution I use is to run the long running tests separately using maven surefire or similar, not through the IDE. This involves checking out the source code somewhere else on my machine and building there.
[*]: Java, how to stop threads, Regarding stopping of a thread
I think a more common solution is to have two test suites: one for the fast tests and another for the slow ones. This is typically the way you divide unit tests (fast) and integration tests (slow).
It's highly unlikely that you'll get modifications to JUnit or IntelliJ for something like this. Better to change the way you use them - it'll get you to an answer faster.
You can modify your thest and do something like
public void theTest(){
if (System.getProperty("skipMyTest") == null){
//execute the test
}
}
and pass the environment variable if you want to skip the test
I'd like to know if there are some unit testing frameworks which are capable of writing multi-threaded tests easily?
I would imagine something like:
invoke a special test method by n threads at the same time for m times. After all test threads finished, an assertion method where some constraints should be validated would be invoked.
My current approach is to create Thread objects inside a junit test method, loop manually the real test cases inside each run() method, wait for all threads and then validate the assertions. But using this, I have a large boilerplate code block for each test.
What are your experiences?
There is ConTest, and also GroboUtils.
I've used GroboUtils many years ago, and it did the job. ConTest is newer, and would be my preferred starting point now, since rather than just relying on trial and error, the instrumentation forces specific interleavings of the threads, providing a deterministic test. In contrast, GroboUtils MultiThreadedTestRunner simply runs the tests and hopes the scheduler produces an interleaving that causes the thread bug to appear.
EDIT: See also ConcuTest which also forces interleavings and is free.
There is also MultithreadedTC by Bill Pugh of FindBugs fame.
Just using the concurrency libraries would simplify your code. You can turn your boiler plate code into one method.
Something like
public static void runAll(int times, Runnable... tests) {
}