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JUnit Jupiter extension. Provides Automated Teardown mechanism.
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package com.tdder.junit.jupiter.extension;

import java.lang.reflect.Executable;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.List;
import java.util.function.Predicate;

import org.junit.jupiter.api.extension.AfterAllCallback;
import org.junit.jupiter.api.extension.AfterEachCallback;
import org.junit.jupiter.api.extension.BeforeAllCallback;
import org.junit.jupiter.api.extension.BeforeEachCallback;
import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.api.extension.ParameterContext;
import org.junit.jupiter.api.extension.ParameterResolutionException;
import org.junit.jupiter.api.extension.ParameterResolver;
import org.junit.jupiter.api.extension.TestInstances;
import org.junit.platform.commons.support.HierarchyTraversalMode;
import org.junit.platform.commons.support.ModifierSupport;
import org.junit.platform.commons.support.ReflectionSupport;

/**
 * JUnit Jupiter extension that tears down test fixtures.
 *
 * This extension is used with {@link TeardownRegistry}.
 * When test adds teardown object to {@link TeardownRegistry}, added teardown object will be executed after test.
 *
 * 
 * Example:
 * 
 *  * @ExtendWith(TeardownExtension.class)
 * class MyTest {
 *
 *     // This field is injected by TeardownExtension.
 *     private TeardownRegistry teardownRegistry;
 *
 *     @Test
 *     void someTest() {
 *         // === Setup ===
 *
 *         // Create test fixture
 *         final FooFixture fooFixture = createFooFixture(...);
 *
 *         // Register tear down code block
 *         teardownRegistry.add(() -> fooFixture.clear());
 *
 *         final BarFixture barFixture = createBarFixture(...);
 *         teardownRegistry.add(() -> barFixture.close());
 *
 *         // ...
 *
 *         // === Exercise ===
 *         // ...
 *
 *         // === Verify ===
 *         // ...
 *
 *         // After tests, either succeeded or failure, all added to TeardownRegistry code blocks are executed.
 *         // The execution order is in reverse order of addition to the TeardownRegistry.
 *     }
 *
 * }
 * 
 *
 * @see TeardownRegistry
 * @author manhole
 */
public class TeardownExtension
        implements ParameterResolver, BeforeAllCallback, AfterAllCallback, BeforeEachCallback, AfterEachCallback {

    private static final ExtensionContext.Namespace NAMESPACE = ExtensionContext.Namespace.create(
            TeardownExtension.class);

    private final Object INSTANCE_STORE_KEY = TeardownExtension.class.getName() + "_INSTANCE";

    private final Object STATIC_STORE_KEY = TeardownExtension.class.getName() + "_STATIC";

    @Override
    public boolean supportsParameter(final ParameterContext parameterContext, final ExtensionContext extensionContext)
            throws ParameterResolutionException {
        final boolean method = parameterContext.getDeclaringExecutable() instanceof Method;
        return parameterContext.getParameter().getType() == TeardownRegistry.class && method;
    }

    @Override
    public Object resolveParameter(final ParameterContext parameterContext, final ExtensionContext extensionContext)
            throws ParameterResolutionException {

        final Executable executable = parameterContext.getDeclaringExecutable();
        if (ModifierSupport.isStatic(executable)) {
            // @BeforeAll
            return resolveParameter(extensionContext, STATIC_STORE_KEY);
        } else {
            // @Before, test method
            return resolveParameter(extensionContext, INSTANCE_STORE_KEY);
        }
    }

    public Object resolveParameter(final ExtensionContext extensionContext, final Object storeKey)
            throws ParameterResolutionException {

        final ExtensionContext.Store store = extensionContext.getStore(NAMESPACE);
        return store.getOrComputeIfAbsent(storeKey, (v) -> new TeardownRegistryImpl(), TeardownRegistryImpl.class);
    }

    @Override
    public void beforeAll(final ExtensionContext extensionContext) throws Exception {
        injectStaticFields(extensionContext);
    }

    @Override
    public void beforeEach(final ExtensionContext extensionContext) throws Exception {
        final TestInstances requiredTestInstances = extensionContext.getRequiredTestInstances();
        final List