Serialize tests during coverage calculation

This generically fixes hcoles/pitest#760 and pitest#73 for all platform engines,
removing the Jupiter specific work-around from pitest#74 and serializing test execution
during coverage calculation using locks. This way the tests can also properly run
in parallel later on during mutant hunting.

pom.xml

@@ -23,7 +23,7 @@
 		<junit.platform.version>1.9.2</junit.platform.version>
 		<junit.version>5.9.2</junit.version>
 		<mockito.version>2.7.6</mockito.version>
-		<pitest.version>1.9.0</pitest.version>
+		<pitest.version>1.13.2</pitest.version>
 		<cucumber.version>5.0.0</cucumber.version>
 		<spock.version>2.3-groovy-4.0</spock.version>
 		<groovy.version>4.0.11</groovy.version>

src/main/java/org/pitest/junit5/JUnit5TestPluginFactory.java

@@ -27,11 +27,10 @@
 public class JUnit5TestPluginFactory implements TestPluginFactory {
 
     @Override
-    public Configuration createTestFrameworkConfiguration(TestGroupConfig config, 
-        ClassByteArraySource source, 
+    public Configuration createTestFrameworkConfiguration(TestGroupConfig config,
+        ClassByteArraySource source,
         Collection<String> excludedRunners,
         Collection<String> includedTestMethods) {
-        System.setProperty("junit.jupiter.execution.parallel.enabled", "false");
         return new JUnit5Configuration(config, includedTestMethods);
     }
 

src/main/java/org/pitest/junit5/JUnit5TestUnitFinder.java

@@ -16,16 +16,24 @@
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.StringJoiner;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.locks.ReentrantLock;
 
 import static java.util.Collections.emptyList;
-import static java.util.Collections.synchronizedList;
+import static java.util.Collections.synchronizedSet;
 import static java.util.Collections.unmodifiableList;
 import static java.util.stream.Collectors.toList;
 
 import org.junit.platform.commons.PreconditionViolationException;
 import org.junit.platform.engine.Filter;
 import org.junit.platform.engine.TestExecutionResult;
+import org.junit.platform.engine.UniqueId;
 import org.junit.platform.engine.discovery.DiscoverySelectors;
 import org.junit.platform.engine.support.descriptor.MethodSource;
 import org.junit.platform.launcher.Launcher;
@@ -35,6 +43,7 @@
 import org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder;
 import org.junit.platform.launcher.core.LauncherFactory;
 import org.pitest.testapi.Description;
+import org.pitest.testapi.NullExecutionListener;
 import org.pitest.testapi.TestGroupConfig;
 import org.pitest.testapi.TestUnit;
 import org.pitest.testapi.TestUnitExecutionListener;
@@ -46,12 +55,27 @@
  */
 public class JUnit5TestUnitFinder implements TestUnitFinder {
 
+    /**
+     * The test group config.
+     */
     private final TestGroupConfig testGroupConfig;
 
+    /**
+     * Test methods that should be included.
+     */
     private final Collection<String> includedTestMethods;
 
+    /**
+     * The JUnit platform launcher used to execute tests.
+     */
     private final Launcher launcher;
 
+    /**
+     * Constructs a new JUnit 5 test unit finder.
+     *
+     * @param testGroupConfig     the test group config
+     * @param includedTestMethods test methods that should be included
+     */
     public JUnit5TestUnitFinder(TestGroupConfig testGroupConfig, Collection<String> includedTestMethods) {
         this.testGroupConfig = testGroupConfig;
         this.includedTestMethods = includedTestMethods;
@@ -64,7 +88,7 @@ public List<TestUnit> findTestUnits(Class<?> clazz, TestUnitExecutionListener ex
             return emptyList();
         }
 
-        List<Filter> filters = new ArrayList<>(2);
+        List<Filter<?>> filters = new ArrayList<>(2);
         try {
             List<String> excludedGroups = testGroupConfig.getExcludedGroups();
             if(excludedGroups != null && !excludedGroups.isEmpty()) {
@@ -84,7 +108,7 @@ public List<TestUnit> findTestUnits(Class<?> clazz, TestUnitExecutionListener ex
         launcher.execute(LauncherDiscoveryRequestBuilder
                 .request()
                 .selectors(DiscoverySelectors.selectClass(clazz))
-                .filters(filters.toArray(new Filter[filters.size()]))
+                .filters(filters.toArray(new Filter[0]))
                 .build(), listener);
 
         return listener.getIdentifiers()
@@ -93,17 +117,92 @@ public List<TestUnit> findTestUnits(Class<?> clazz, TestUnitExecutionListener ex
                 .collect(toList());
     }
 
+    /**
+     * A test execution listener that listens for test identifiers, supporting atomic test units
+     * and notifying the supplied test unit execution listener so that for example coverage can
+     * be recorded right away during discovery phase already.
+     */
     private class TestIdentifierListener implements TestExecutionListener {
+        /**
+         * The test class as given to the test unit finder for forwarding to the test unit execution listener.
+         */
         private final Class<?> testClass;
-        private final TestUnitExecutionListener l;
-        private final List<TestIdentifier> identifiers = synchronizedList(new ArrayList<>());
 
-        public TestIdentifierListener(Class<?> testClass, TestUnitExecutionListener l) {
+        /**
+         * The test unit execution listener, that for example is used for coverage recording per test.
+         */
+        private final TestUnitExecutionListener testUnitExecutionListener;
+
+        /**
+         * The collected test identifiers.
+         */
+        private final Set<TestIdentifier> identifiers = synchronizedSet(new LinkedHashSet<>());
+
+        /**
+         * Whether to serialize test execution, because we are during coverage recording which is
+         * done through static fields and thus does not support parallel test execution.
+         */
+        private final boolean serializeExecution;
+
+        /**
+         * A map that holds the locks that child tests of locked parent tests should use.
+         * For example parallel data-driven Spock features start the feature execution which is CONTAINER_AND_TEST,
+         * then wait for the parallel iteration executions to be finished which are TEST,
+         * then finish the feature execution.
+         * Due to that we cannot lock the iteration executions on the same lock as the feature executions,
+         * as the feature execution is around all the subordinate iteration executions.
+         *
+         * <p>This logic will of course break if there is some test engine that does strange setups like
+         * having CONTAINER_AND_TEST with child CONTAINER that have child TEST and similar.
+         * If those engines happen to be used, tests will start to deadlock, as the grand-child test
+         * would not find the parent serializer and thus use the root serializer on which the grand-parent
+         * CONTAINER_AND_TEST already locks.
+         *
+         * <p>This setup would probably not make much sense, so should not be taken into account
+         * unless such an engine actually pops up. If it does and someone tries to use it with PIT,
+         * the logic should maybe be made more sophisticated like remembering the parent-child relationships
+         * to be able to find the grand-parent serializer which is not possible stateless, because we are
+         * only able to get the parent identifier directly, but not further up stateless.
+         */
+        private final Map<UniqueId, AtomicReference<ReentrantLock>> parentCoverageSerializers = new ConcurrentHashMap<>();
+
+        /**
+         * A map that holds the actual lock used for a specific test to be able to easily and safely unlock
+         * without the need to recalculate which lock to use.
+         */
+        private final Map<UniqueId, ReentrantLock> coverageSerializers = new ConcurrentHashMap<>();
+
+        /**
+         * The root coverage serializer to be used for the top-most recorded tests.
+         */
+        private final ReentrantLock rootCoverageSerializer = new ReentrantLock();
+
+        /**
+         * Constructs a new test identifier listener.
+         *
+         * @param testClass                 the test class as given to the test unit finder for forwarding to the result collector
+         * @param testUnitExecutionListener the test unit execution listener to notify during test execution
+         */
+        public TestIdentifierListener(Class<?> testClass, TestUnitExecutionListener testUnitExecutionListener) {
             this.testClass = testClass;
-            this.l = l;
+            this.testUnitExecutionListener = testUnitExecutionListener;
+            // PIT gives a coverage recording listener here during coverage recording
+            // At the later stage during minion hunting a NullExecutionListener is given
+            // as PIT is only interested in the resulting list of identifiers.
+            // Serialization of test execution is only necessary during coverage calculation
+            // currently. To be on the safe side serialize test execution for any listener
+            // type except listener types where we know tests can run in parallel safely,
+            // i.e. currently the NullExecutionListener which is the only other one besides
+            // the coverage recording listener.
+            serializeExecution = !(testUnitExecutionListener instanceof NullExecutionListener);
         }
 
-        List<TestIdentifier> getIdentifiers() {
+        /**
+         * Returns the collected test identifiers.
+         *
+         * @return the collected test identifiers
+         */
+        private List<TestIdentifier> getIdentifiers() {
             return unmodifiableList(new ArrayList<>(identifiers));
         }
 
@@ -117,25 +216,59 @@ public void executionStarted(TestIdentifier testIdentifier) {
                         && !includedTestMethods.contains(((MethodSource)testIdentifier.getSource().get()).getMethodName())) {
                     return;
                 }
-                l.executionStarted(new Description(testIdentifier.getUniqueId(), testClass));
+
+                if (serializeExecution) {
+                    coverageSerializers.compute(testIdentifier.getUniqueIdObject(), (uniqueId, lock) -> {
+                        if (lock != null) {
+                            throw new AssertionError("No lock should be present");
+                        }
+
+                        // find the serializer to lock the test on
+                        // if there is a parent test locked, use the lock for its children if not,
+                        // use the root serializer
+                        return testIdentifier
+                                .getParentIdObject()
+                                .map(parentCoverageSerializers::get)
+                                .map(lockRef -> lockRef.updateAndGet(parentLock ->
+                                        parentLock == null ? new ReentrantLock() : parentLock))
+                                .orElse(rootCoverageSerializer);
+                    }).lock();
+                    // record a potential serializer for child tests to lock on
+                    parentCoverageSerializers.put(testIdentifier.getUniqueIdObject(), new AtomicReference<>());
+                }
+
+                testUnitExecutionListener.executionStarted(new Description(testIdentifier.getUniqueId(), testClass), true);
                 identifiers.add(testIdentifier);
             }
         }
 
-
         @Override
         public void executionFinished(TestIdentifier testIdentifier, TestExecutionResult testExecutionResult) {
             // Classes with failing BeforeAlls never start execution and identify as 'containers' not 'tests'
             if (testExecutionResult.getStatus() == TestExecutionResult.Status.FAILED) {
-                if (!identifiers.contains(testIdentifier)) {
-                    identifiers.add(testIdentifier);
-                }
-                l.executionFinished(new Description(testIdentifier.getUniqueId(), testClass), false);
+                identifiers.add(testIdentifier);
+                testUnitExecutionListener.executionFinished(new Description(testIdentifier.getUniqueId(), testClass), false);
             } else if (testIdentifier.isTest()) {
-                l.executionFinished(new Description(testIdentifier.getUniqueId(), testClass), true);
+                testUnitExecutionListener.executionFinished(new Description(testIdentifier.getUniqueId(), testClass), true);
             }
-        }
 
+            if (serializeExecution) {
+                // forget the potential serializer for child tests
+                parentCoverageSerializers.remove(testIdentifier.getUniqueIdObject());
+                // unlock the serializer for the finished tests to let the next test continue
+                ReentrantLock lock = coverageSerializers.remove(testIdentifier.getUniqueIdObject());
+                if (lock != null) {
+                    lock.unlock();
+                }
+            }
+        }
     }
 
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", JUnit5TestUnitFinder.class.getSimpleName() + "[", "]")
+                .add("testGroupConfig=" + testGroupConfig)
+                .add("includedTestMethods=" + includedTestMethods)
+                .toString();
+    }
 }