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Check that JUnit Extension throws specific Exception

Suppose I develop an extension which disallows test method names to start with an uppercase character.
public class DisallowUppercaseLetterAtBeginning implements BeforeEachCallback {
#Override
public void beforeEach(ExtensionContext context) {
char c = context.getRequiredTestMethod().getName().charAt(0);
if (Character.isUpperCase(c)) {
throw new RuntimeException("test method names should start with lowercase.");
}
}
}
Now I want to test that my extension works as expected.
#ExtendWith(DisallowUppercaseLetterAtBeginning.class)
class MyTest {
#Test
void validTest() {
}
#Test
void TestShouldNotBeCalled() {
fail("test should have failed before");
}
}
How can I write a test to verify that the attempt to execute the second method throws a RuntimeException with a specific message?

Another approach could be to use the facilities provided by the new JUnit 5 - Jupiter framework.
I put below the code which I tested with Java 1.8 on Eclipse Oxygen. The code suffers from a lack of elegance and conciseness but could hopefully serve as a basis to build a robust solution for your meta-testing use case.
Note that this is actually how JUnit 5 is tested, I refer you to the unit tests of the Jupiter engine on Github.
public final class DisallowUppercaseLetterAtBeginningTest {
#Test
void testIt() {
// Warning here: I checked the test container created below will
// execute on the same thread as used for this test. We should remain
// careful though, as the map used here is not thread-safe.
final Map<String, TestExecutionResult> events = new HashMap<>();
EngineExecutionListener listener = new EngineExecutionListener() {
#Override
public void executionFinished(TestDescriptor descriptor, TestExecutionResult result) {
if (descriptor.isTest()) {
events.put(descriptor.getDisplayName(), result);
}
// skip class and container reports
}
#Override
public void reportingEntryPublished(TestDescriptor testDescriptor, ReportEntry entry) {}
#Override
public void executionStarted(TestDescriptor testDescriptor) {}
#Override
public void executionSkipped(TestDescriptor testDescriptor, String reason) {}
#Override
public void dynamicTestRegistered(TestDescriptor testDescriptor) {}
};
// Build our test container and use Jupiter fluent API to launch our test. The following static imports are assumed:
//
// import static org.junit.platform.engine.discovery.DiscoverySelectors.selectClass
// import static org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder.request
JupiterTestEngine engine = new JupiterTestEngine();
LauncherDiscoveryRequest request = request().selectors(selectClass(MyTest.class)).build();
TestDescriptor td = engine.discover(request, UniqueId.forEngine(engine.getId()));
engine.execute(new ExecutionRequest(td, listener, request.getConfigurationParameters()));
// Bunch of verbose assertions, should be refactored and simplified in real code.
assertEquals(new HashSet<>(asList("validTest()", "TestShouldNotBeCalled()")), events.keySet());
assertEquals(Status.SUCCESSFUL, events.get("validTest()").getStatus());
assertEquals(Status.FAILED, events.get("TestShouldNotBeCalled()").getStatus());
Throwable t = events.get("TestShouldNotBeCalled()").getThrowable().get();
assertEquals(RuntimeException.class, t.getClass());
assertEquals("test method names should start with lowercase.", t.getMessage());
}
Though a little verbose, one advantage of this approach is it doesn't require mocking and execute the tests in the same JUnit container as will be used later for real unit tests.
With a bit of clean-up, a much more readable code is achievable. Again, JUnit-Jupiter sources can be a great source of inspiration.

If the extension throws an exception then there's not much a #Test method can do since the test runner will never reach the #Test method. In this case, I think, you have to test the extension outside of its use in the normal test flow i.e. let the extension be the SUT.
For the extension provided in your question, the test might be something like this:
#Test
public void willRejectATestMethodHavingANameStartingWithAnUpperCaseLetter() throws NoSuchMethodException {
ExtensionContext extensionContext = Mockito.mock(ExtensionContext.class);
Method method = Testable.class.getMethod("MethodNameStartingWithUpperCase");
Mockito.when(extensionContext.getRequiredTestMethod()).thenReturn(method);
DisallowUppercaseLetterAtBeginning sut = new DisallowUppercaseLetterAtBeginning();
RuntimeException actual =
assertThrows(RuntimeException.class, () -> sut.beforeEach(extensionContext));
assertThat(actual.getMessage(), is("test method names should start with lowercase."));
}
#Test
public void willAllowTestMethodHavingANameStartingWithAnLowerCaseLetter() throws NoSuchMethodException {
ExtensionContext extensionContext = Mockito.mock(ExtensionContext.class);
Method method = Testable.class.getMethod("methodNameStartingWithLowerCase");
Mockito.when(extensionContext.getRequiredTestMethod()).thenReturn(method);
DisallowUppercaseLetterAtBeginning sut = new DisallowUppercaseLetterAtBeginning();
sut.beforeEach(extensionContext);
// no exception - good enough
}
public class Testable {
public void MethodNameStartingWithUpperCase() {
}
public void methodNameStartingWithLowerCase() {
}
}
However, your question suggests that the above extension is only an example so, more generally; if your extension has a side effect (e.g. sets something in an addressable context, populates a System property etc) then your #Test method could assert that this side effect is present. For example:
public class SystemPropertyExtension implements BeforeEachCallback {
#Override
public void beforeEach(ExtensionContext context) {
System.setProperty("foo", "bar");
}
}
#ExtendWith(SystemPropertyExtension.class)
public class SystemPropertyExtensionTest {
#Test
public void willSetTheSystemProperty() {
assertThat(System.getProperty("foo"), is("bar"));
}
}
This approach has the benefit of side stepping the potentially awkward setup steps of: creating the ExtensionContext and populating it with the state required by your test but it may come at the cost of limiting the test coverage since you can really only test one outcome. And, of course, it is only feasible if the extension has a side effect which can be evaulated in a test case which uses the extension.
So, in practice, I suspect you might need a combination of these approaches; for some extensions the extension can be the SUT and for others the extension can be tested by asserting against its side effect(s).

After trying the solutions in the answers and the question linked in the comments, I ended up with a solution using the JUnit Platform Launcher.
class DisallowUppercaseLetterAtBeginningTest {
#Test
void should_succeed_if_method_name_starts_with_lower_case() {
TestExecutionSummary summary = runTestMethod(MyTest.class, "validTest");
assertThat(summary.getTestsSucceededCount()).isEqualTo(1);
}
#Test
void should_fail_if_method_name_starts_with_upper_case() {
TestExecutionSummary summary = runTestMethod(MyTest.class, "InvalidTest");
assertThat(summary.getTestsFailedCount()).isEqualTo(1);
assertThat(summary.getFailures().get(0).getException())
.isInstanceOf(RuntimeException.class)
.hasMessage("test method names should start with lowercase.");
}
private TestExecutionSummary runTestMethod(Class<?> testClass, String methodName) {
SummaryGeneratingListener listener = new SummaryGeneratingListener();
LauncherDiscoveryRequest request = request().selectors(selectMethod(testClass, methodName)).build();
LauncherFactory.create().execute(request, listener);
return listener.getSummary();
}
#ExtendWith(DisallowUppercaseLetterAtBeginning.class)
static class MyTest {
#Test
void validTest() {
}
#Test
void InvalidTest() {
fail("test should have failed before");
}
}
}
JUnit itself will not run MyTest because it is an inner class without #Nested. So there are no failing tests during the build process.
Update
JUnit itself will not run MyTest because it is an inner class without #Nested. So there are no failing tests during the build process.
This is not completly correct. JUnit itself would also run MyTest, e.g. if "Run All Tests" is started within the IDE or within a Gradle build.
The reason why MyTest was not executed is because I used Maven and I tested it with mvn test. Maven uses the Maven Surefire Plugin to execute tests. This plugin has a default configuration which excludes all nested classes like MyTest.
See also this answer about "Run tests from inner classes via Maven" and the linked issues in the comments.

JUnit 5.4 introduced the JUnit Platform Test Kit which allows you to execute a test plan and inspect the results.
To take a dependency on it from Gradle, it might look something like this:
testImplementation("org.junit.platform:junit-platform-testkit:1.4.0")
And using your example, your extension test could look something like this:
import org.junit.jupiter.api.extension.ExtendWith
import org.junit.jupiter.api.fail
import org.junit.platform.engine.discovery.DiscoverySelectors
import org.junit.platform.testkit.engine.EngineTestKit
import org.junit.platform.testkit.engine.EventConditions
import org.junit.platform.testkit.engine.TestExecutionResultConditions
internal class DisallowUpperCaseExtensionTest {
#Test
internal fun `succeed if starts with lower case`() {
val results = EngineTestKit
.engine("junit-jupiter")
.selectors(
DiscoverySelectors.selectMethod(ExampleTest::class.java, "validTest")
)
.execute()
results.tests().assertStatistics { stats ->
stats.finished(1)
}
}
#Test
internal fun `fail if starts with upper case`() {
val results = EngineTestKit
.engine("junit-jupiter")
.selectors(
DiscoverySelectors.selectMethod(ExampleTest::class.java, "TestShouldNotBeCalled")
)
.execute()
results.tests().assertThatEvents()
.haveExactly(
1,
EventConditions.finishedWithFailure(
TestExecutionResultConditions.instanceOf(java.lang.RuntimeException::class.java),
TestExecutionResultConditions.message("test method names should start with lowercase.")
)
)
}
#ExtendWith(DisallowUppercaseLetterAtBeginning::class)
internal class ExampleTest {
#Test
fun validTest() {
}
#Test
fun TestShouldNotBeCalled() {
fail("test should have failed before")
}
}
}

JUnit5 - How to get test result in AfterTestExecutionCallback

I write JUnit5 Extension. But I cannot find way how to obtain test result.
Extension looks like this:
import org.junit.jupiter.api.extension.AfterTestExecutionCallback;
import org.junit.jupiter.api.extension.TestExtensionContext;
public class TestResultExtension implements AfterTestExecutionCallback {
#Override
public void afterTestExecution(TestExtensionContext context) throws Exception {
//How to get test result? SUCCESS/FAILED
}
}
Any hints how to obtain test result?

This work for me:
public class RunnerExtension implements AfterTestExecutionCallback {
#Override
public void afterTestExecution(ExtensionContext context) throws Exception {
Boolean testResult = context.getExecutionException().isPresent();
System.out.println(testResult); //false - SUCCESS, true - FAILED
}
}
#ExtendWith(RunnerExtension.class)
public abstract class Tests {
}

As other answers point out, JUnit communicates failed tests with exceptions, so an AfterTestExecutionCallback can be used to gleam what happened. Note that this is error prone as extension running later might still fail the test.
Another way to do that is to register a custom TestExecutionListener. Both of these approaches are a little roundabout, though. There is an issue that tracks a specific extension point for reacting to test results, which would likely be the most straight-forward answer to your question. If you can provide a specific use case, it would be great if you could head over to #542 and leave a comment describing it.

You can use SummaryGeneratingListener from org.junit.platform.launcher.listeners
It contains MutableTestExecutionSummary field, which implements TestExecutionSummary interface, and this way you can obtain info about containers, tests, time, failures etc.
You can create custom listener, for example:
Create class that extends SummaryGeneratingListener
public class ResultAnalyzer extends SummaryGeneratingListener {
#Override
public void testPlanExecutionFinished(TestPlan testPlan) {
//This method is invoked after all tests in all containers is finished
super.testPlanExecutionFinished(testPlan);
analyzeResult();
}
private void analyzeResult() {
var summary = getSummary();
var failures = summary.getFailures();
//Do something
}
}
Register listener by creating file
src\main\resources\META-INF\services\org.junit.platform.launcher.TestExecutionListener
and specify your implementation in it
path.to.class.ResultAnalyzer
Enable auto-detection of extensions, set parameter
-Djunit.jupiter.extensions.autodetection.enabled=true
And that's it!
Docs
https://junit.org/junit5/docs/5.0.0/api/org/junit/platform/launcher/listeners/SummaryGeneratingListener.html
https://junit.org/junit5/docs/5.0.0/api/org/junit/platform/launcher/listeners/TestExecutionSummary.html
https://junit.org/junit5/docs/current/user-guide/#extensions-registration-automatic

I have only this solution:
String testResult = context.getTestException().isPresent() ? "FAILED" : "OK";
It seems that it works well. But I am not sure if it will work correctly in all situations.

Fails in JUnit are propagated with exceptions. There are several exceptions, which indicate various types of errors.
So an exception in TestExtensionContext#getTestException() indicates an error. The method can't manipulate actual test results, so depending on your use case you might want to implement TestExecutionExceptionHandler, which allows you to swallow exceptions, thus changing whether a test succeeded or not.

You're almost there.
To implement a test execution callback and get the test result for logging (or generating a report) you can do the following:
import org.junit.jupiter.api.extension.AfterTestExecutionCallback;
import org.junit.jupiter.api.extension.ExtensionContext;
public class TestResultExtension implements AfterTestExecutionCallback
{
#Override
public void afterTestExecution(ExtensionContext context) throws Exception
{
// check the context for an exception
Boolean passed = context.getExecutionException().isEmpty();
// if there isn't, the test passed
String result = passed ? "PASSED" : "FAILED";
// now that you have the result, you can do whatever you want
System.out.println("Test Result: " + context.getDisplayName() + " " + result);
}
}
And then you just add the TestResultExtension using the #ExtendWith() annotation for your test cases:
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import static org.junit.jupiter.api.Assertions.assertTrue;
#ExtendWith(TestResultExtension.class)
public class SanityTest
{
#Test
public void testSanity()
{
assertTrue(true);
}
#Test
public void testInsanity()
{
assertTrue(false);
}
}
It's a good idea to extend a base test that includes the extension
import org.junit.jupiter.api.extension.ExtendWith;
#ExtendWith(TestResultExtension.class)
public class BaseTest
{}
And then you don't need to include the annotation in every test:
public class SanityTest extends BaseTest
{ //... }

How to use JUnit4TestAdapter with objects

I am trying to write a test suite using JUnit4 by relying on JUnit4TestAdapter. Having a look at the code of this class I saw that it only works with a Class as input. I would like to build a test class and set a parameter on it before running it with my TestSuite. Unfortunately, Junit4TestAdapter is building the test by using reflection (not 100% sure about the mechanism behind it), which means that I cannot change my test class on runtime.
Has anybody done anything similar before? Is there any possible workaround to this issue? Thanks for your help!
public class SimpleTest {
#Test
public void testBasic() {
TemplateTester tester = new TemplateTester();
ActionIconsTest test = new ActionIconsTest();
test.setParameter("New Param Value");
tester.addTests(test);
tester.run();
}
}
/////
public class TemplateTester {
private TestSuite suite;
public TemplateTester() {
suite = new TestSuite();
}
public void addTests(TemplateTest... tests) {
for (TemplateTest test : tests) {
suite.addTest(new JUnit4TestAdapter(test.getClass()));
}
}
public void run() {
suite.run(new TestResult());
}
}
/////
public interface TemplateTest {
}
/////
public class ActionIconsTest extends BaseTestStrategy implements TemplateTest {
#Test
public void icons() {
//Test logic here
}
public void navigateToTestPage() {
//Here I need the parameter
}
}
/////
public abstract class BaseTestStrategy {
protected String parameter;
#Before
public void init() {
navigateToTestPage();
}
public abstract void navigateToTestPage();
public void setParameter(String parameter) {
this.parameter = parameter;
}
}
I am trying to test a web application with Selenium. The way I want to test is by splitting the functionality, e.g., I want to test the available icons (ActionIconsTest), then I'd like to test other parts like buttons, etc.
The idea behind this is to have a better categorization of the functionality available in certain screen. This is quite coupled with the way we are currently developing our web app.
With this in mind, TemplateTest is just an interface implemented by the different kind of tests (ActionIconTest, ButtonTest, etc) available in my system.
TemplateTester is a Junit suite test with all the different tests that implement the interface TemplateTest.
The reason for this question is because I was trying to implement a Strategy pattern and then realized of the inconvenient of passing a class to Junit4TestAdapter in runtime.

Well, taking in account that JUNIT needs your tester's Class object as an object factory (so he can create several instances of your tester), I can only suggest you pass parameters to your tester through System Properties.
Moreover, it's the recommended way of passing parameters: http://junit.org/faq.html#running_7

JUnit: Run one test with different configurations

I have 2 test methods, and i need to run them with different configurations
myTest() {
.....
.....
}
#Test
myTest_c1() {
setConf1();
myTest();
}
#Test
myTest_c2() {
setConf2();
myTest();
}
//------------------
nextTest() {
.....
.....
}
#Test
nextTest_c1() {
setConf1();
nextTest();
}
#Test
nextTest_c2() {
setConf2();
nextTest();
}
I cannot run them both from one config (as in code below) because i need separate methods for tosca execution.
#Test
tests_c1() {
setConf1();
myTest()
nextTest();
}
I don't want to write those 2 methods to run each test, how can i solve this?
First i thought to write custom annotation
#Test
#RunWithBothConf
myTest() {
....
}
But maybe there are any other solutions for this?

What about using Theories?
#RunWith(Theories.class)
public class MyTest{
private static enum Configs{
C1, C2, C3;
}
#DataPoints
public static Configs[] configValues = Configs.values();
private void doConfig(Configs config){
swich(config){...}
}
#Theory
public void test1(Config config){
doConfig(config);
// rest of test
}
#Theory
public void test2(Config config){
doConfig(config);
// rest of test
}
Not sure why formatting if off.

I have a similar issue in a bunch of test cases I have, where certain tests need to be run with different configurations. Now, 'configuration' in your case might be more like settings, in which case maybe this isn't the best option, but for me it's more like a deployment model, so it fits.
Create a base class containing the tests.
Extend the base class with one that represents the different configuration.
As you execute each of the derived classes, the tests in the base class will be run with the configuration setup in its own class.
To add new tests, you just need to add them to the base class.

Here is how I would approach it:
Create two test classes
The first class configures to conf1 but uses the #Before attribute trigger the setup
The second class extends the first but overrides the configure method
In the example below I have a single member variable conf. If no configuration is run it stays at its default value 0. setConf1 is now setConf in the Conf1Test class which sets this variable to 1. setConf2 is now setConf in the Conf2Test class.
Here is the main test class:
public class Conf1Test
{
protected int conf = 0;
#Before
public void setConf()
{
conf = 1;
}
#Test
public void myTest()
{
System.out.println("starting myTest; conf=" + conf);
}
#Test
public void nextTest()
{
System.out.println("starting nextTest; conf=" + conf);
}
}
And the second test class
public class Conf2Test extends Conf1Test
{
// override setConf to do "setConf2" function
public void setConf()
{
conf = 2;
}
}
When I configure my IDE to run all tests in the package I get the following output:
starting myTest; conf=1
starting nextTest; conf=1
starting myTest; conf=2
starting nextTest; conf=2
I think this gives you what. Each test only has to be written once. Each test gets run twice, once with conf1 and once with conf2

The way you have it right now seems fine to me. You aren't duplicating any code, and each test is clear and easy to understand.

Is there a way to make Eclipse run a JUnit test multiple times until failure?

We occasionally have bugs that appear once in every X runs. Before people check in stuff (where it is automatically JUnit'd), our devs need to pass JUnit locally via Eclipse.
Is there some convenient way (built in or high-quality Plugin) to make Eclipse run the same test X times and stop if there's a failure? An alternative to just clicking Run X times?
Note that I'm looking for something in the UI (e.g., right click and say "Run X times" instead of just "Run").

If the for loop works, then I agree with nos.
If you need to repeat the entire setup-test-teardown, then you can use a TestSuite:
Right-click on the package containing the test to repeat
Go to New and choose to create a JUnit test SUITE
Make sure that only the test you want to repeat is selected and click through to finish.
Edit the file to run it multiple times.
In the file you just find the
addTestSuite(YourTestClass.class)
line, and wrap that in a for loop.
I'm pretty sure that you can use addTest instead of addTestSuite to get it to only run one test from that class if you just want to repeat a single test method.

If you really want to run a test class until failure, you need your own runner.
#RunWith(RunUntilFailure.class)
public class YourClass {
// ....
}
which could be implemented as follows...
package com.example;
import org.junit.internal.runners.*;
import org.junit.runner.notification.*;
import org.junit.runner.*;
public class RunUntilFailure extends Runner {
private TestClassRunner runner;
public RunUntilFailure(Class<?> klass) throws InitializationError {
this.runner = new TestClassRunner(klass);
}
#Override
public Description getDescription() {
Description description = Description.createSuiteDescription("Run until failure");
description.addChild(runner.getDescription());
return description;
}
#Override
public void run(RunNotifier notifier) {
class L extends RunListener {
boolean fail = false;
public void testFailure(Failure failure) throws Exception { fail = true; }
}
L listener = new L();
notifier.addListener(listener);
while (!listener.fail) runner.run(notifier);
}
}
...releasing untested code, feeling TDD guilt :)

Based on #akuhn's answer, here is what I came up with - rather than running forever, this will run 50 times or until failure, whichever comes first.
package com.foo
import org.junit.runner.Description;
import org.junit.runner.Runner;
import org.junit.runner.notification.Failure;
import org.junit.runner.notification.RunListener;
import org.junit.runner.notification.RunNotifier;
import org.junit.runners.BlockJUnit4ClassRunner;
import org.junit.runners.model.InitializationError;
public class RunManyTimesUntilFailure extends Runner {
private static final int MAX_RUN_COUNT = 50;
private BlockJUnit4ClassRunner runner;
#SuppressWarnings("unchecked")
public RunManyTimesUntilFailure(final Class testClass) throws InitializationError {
runner = new BlockJUnit4ClassRunner(testClass);
}
#Override
public Description getDescription() {
final Description description = Description.createSuiteDescription("Run many times until failure");
description.addChild(runner.getDescription());
return description;
}
#Override
public void run(final RunNotifier notifier) {
class L extends RunListener {
boolean shouldContinue = true;
int runCount = 0;
#Override
public void testFailure(#SuppressWarnings("unused") final Failure failure) throws Exception {
shouldContinue = false;
}
#Override
public void testFinished(#SuppressWarnings("unused") Description description) throws Exception {
runCount++;
shouldContinue = (shouldContinue && runCount < MAX_RUN_COUNT);
}
}
final L listener = new L();
notifier.addListener(listener);
while (listener.shouldContinue) {
runner.run(notifier);
}
}
}

I know it doesn't answer the question directly but if a test isn't passing every time it is run it is a test smell known as Erratic Test. There are several possible causes for this (from xUnit Test Patterns):
Interacting Tests
Interacting Test Suites
Lonely Test
Resource Leakage
Resource Optimism
Unrepeatable Test
Test Run War
Nondeterministic Test
The details of each of these is documented in Chapter 16 of xUnit Test Patterns.

Here is a post I wrote that shows several ways of running the tests repeatedly with code examples:
http://codehowtos.blogspot.com/2011/04/run-junit-test-repeatedly.html
You can use the #Parametrized runner, or use the special runner included in the post
There is also a reference to a #Retry implementation

I don't believe there's a built in way for junit to do exactly what you're asking for.
If multiple runs produce different result, you should have a unit test testing that case. Wich might be as simple as running a for loop in the relevant test cases.

It is possible to implement such an loop with TestRules (since JUnit 4.9)
A very simple implementation that runs every Test 10 times:
import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;
public class SimpleRepeatRule implements TestRule {
private static class SimpleRepeatStatement extends Statement {
private final Statement statement;
private SimpleRepeatStatement(Statement statement) {
this.statement = statement;
}
#Override
public void evaluate() throws Throwable {
for (int i = 0; i < 10; i++) {
statement.evaluate();
}
}
}
#Override
public Statement apply(Statement statement, Description description) {
return new SimpleRepeatStatement(statement);
}
}
usage:
public class Run10TimesTest {
#Rule
public SimpleRepeatRule repeatRule = new SimpleRepeatRule();
#Test
public void myTest(){...}
}
For a more useful implementation based on an annotation that define which test method has to been executed how often have a look at this blog:
http://www.codeaffine.com/2013/04/10/running-junit-tests-repeatedly-without-loops/