Make AppEngineRule work with JUnit 5 (#548)

* Make AppEngineRule work with JUnit 5

Made AppEngineRule work with both JUnit4 and JUnit 5 and applied
it to PremiumListTest.

Next step is to convert SqlIntegrationTestSuite.java to JUnit5.

core/src/test/java/google/registry/model/registry/label/PremiumListTest.java

@@ -29,16 +29,14 @@ import google.registry.model.registry.label.PremiumList.PremiumListEntry;
 import google.registry.model.registry.label.PremiumList.PremiumListRevision;
 import google.registry.testing.AppEngineRule;
 import org.joda.money.Money;
-import org.junit.Rule;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.migrationsupport.rules.EnableRuleMigrationSupport;
+import org.junit.jupiter.api.extension.RegisterExtension;
 
 /** Unit tests for {@link PremiumList}. */
-@EnableRuleMigrationSupport
 public class PremiumListTest {
 
-  @Rule
+  @RegisterExtension
   public final AppEngineRule appEngine = AppEngineRule.builder().withDatastoreAndCloudSql().build();
 
   @BeforeEach

core/src/test/java/google/registry/persistence/transaction/JpaEntityCoverage.java

@@ -27,6 +27,7 @@ import java.sql.SQLException;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.function.Supplier;
 import javax.persistence.Entity;
 import org.junit.rules.ExternalResource;
 
@@ -51,15 +52,15 @@ public class JpaEntityCoverage extends ExternalResource {
   private static final Map<String, Boolean> testsJpaEntities = Maps.newHashMap();
 
   // Provides class name of the test being executed.
-  private final TestCaseWatcher watcher;
+  private final Supplier<String> currTestClassNameSupplier;
 
-  public JpaEntityCoverage(TestCaseWatcher watcher) {
-    this.watcher = watcher;
+  public JpaEntityCoverage(Supplier<String> currTestClassNameSupplier) {
+    this.currTestClassNameSupplier = currTestClassNameSupplier;
   }
 
   @Override
   public void before() {
-    testsJpaEntities.putIfAbsent(watcher.getTestClass(), false);
+    testsJpaEntities.putIfAbsent(currTestClassNameSupplier.get(), false);
   }
 
   @Override
@@ -69,7 +70,7 @@ public class JpaEntityCoverage extends ExternalResource {
         .forEach(
             entity -> {
               allCoveredJpaEntities.add(entity);
-              testsJpaEntities.put(watcher.getTestClass(), true);
+              testsJpaEntities.put(currTestClassNameSupplier.get(), true);
             });
   }
 

core/src/test/java/google/registry/persistence/transaction/JpaTestRules.java

@@ -29,6 +29,9 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import org.joda.time.DateTime;
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.BeforeEachCallback;
+import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.rules.RuleChain;
 import org.junit.rules.TestRule;
 import org.junit.runner.Description;
@@ -88,7 +91,7 @@ public class JpaTestRules {
       this.ruleChain =
           RuleChain.outerRule(watcher)
               .around(integrationTestRule)
-              .around(new JpaEntityCoverage(watcher));
+              .around(new JpaEntityCoverage(watcher::getTestClass));
     }
 
     @Override
@@ -97,6 +100,40 @@ public class JpaTestRules {
     }
   }
 
+  /**
+   * JUnit extension for member classes of {@link
+   * google.registry.schema.integration.SqlIntegrationTestSuite}. In addition to providing a
+   * database through {@link JpaIntegrationTestRule}, it also keeps track of the test coverage of
+   * the declared JPA entities (in persistence.xml). Per-class statistics are stored in static
+   * variables. The SqlIntegrationTestSuite inspects the cumulative statistics after all test
+   * classes have run.
+   */
+  public static final class JpaIntegrationWithCoverageExtension
+      implements BeforeEachCallback, AfterEachCallback {
+    private String currentTestClassName = null;
+    private final JpaEntityCoverage jpaEntityCoverage =
+        new JpaEntityCoverage(() -> this.currentTestClassName);
+    private final JpaIntegrationTestRule integrationTestRule;
+
+    JpaIntegrationWithCoverageExtension(JpaIntegrationTestRule integrationTestRule) {
+      this.integrationTestRule = integrationTestRule;
+    }
+
+    @Override
+    public void beforeEach(ExtensionContext context) throws Exception {
+      this.currentTestClassName = context.getRequiredTestClass().getName();
+      integrationTestRule.before();
+      jpaEntityCoverage.before();
+    }
+
+    @Override
+    public void afterEach(ExtensionContext context) throws Exception {
+      jpaEntityCoverage.after();
+      integrationTestRule.after();
+      this.currentTestClassName = null;
+    }
+  }
+
   /** Builder of test rules that provide {@link JpaTransactionManager}. */
   public static class Builder {
     private String initScript;
@@ -149,6 +186,15 @@ public class JpaTestRules {
       return new JpaIntegrationWithCoverageRule(buildIntegrationTestRule());
     }
 
+    /**
+     * JUnit extension that adapts {@link JpaIntegrationTestRule} for JUnit 5 and also checks test
+     * coverage of JPA entity classes.
+     */
+    public JpaIntegrationWithCoverageExtension buildIntegrationWithCoverageExtension() {
+      checkState(initScript == null, "Integration tests do not accept initScript");
+      return new JpaIntegrationWithCoverageExtension(buildIntegrationTestRule());
+    }
+
     /** Builds a {@link JpaUnitTestRule} instance. */
     public JpaUnitTestRule buildUnitTestRule() {
       checkState(

core/src/test/java/google/registry/testing/AppEngineRule.java

@@ -14,6 +14,7 @@
 
 package google.registry.testing;
 
+import static com.google.common.base.Preconditions.checkState;
 import static com.google.common.truth.Truth.assertWithMessage;
 import static google.registry.testing.DatastoreHelper.persistSimpleResources;
 import static google.registry.util.ResourceUtils.readResourceUtf8;
@@ -40,6 +41,7 @@ import google.registry.model.registrar.Registrar.State;
 import google.registry.model.registrar.RegistrarAddress;
 import google.registry.model.registrar.RegistrarContact;
 import google.registry.persistence.transaction.JpaTestRules;
+import google.registry.persistence.transaction.JpaTestRules.JpaIntegrationWithCoverageExtension;
 import google.registry.persistence.transaction.JpaTestRules.JpaIntegrationWithCoverageRule;
 import google.registry.util.Clock;
 import java.io.ByteArrayInputStream;
@@ -53,6 +55,9 @@ import javax.annotation.Nullable;
 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.BeforeEachCallback;
+import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.rules.ExternalResource;
 import org.junit.rules.TemporaryFolder;
 import org.junit.runner.Description;
@@ -66,9 +71,15 @@ import org.junit.runners.model.Statement;
  *
  * <p>This rule also resets global Objectify for the current thread.
  *
+ * <p>This class works with both JUnit 4 and JUnit 5. With JUnit 4, the test runner calls {@link
+ * #apply(Statement, Description)}, which in turns calls {@link #before()} on entry and {@link
+ * #after()} on exit. With JUnit 5, the test runner calls {@link #beforeEach(ExtensionContext)} and
+ * {@link #afterEach(ExtensionContext)}.
+ *
  * @see org.junit.rules.ExternalResource
  */
-public final class AppEngineRule extends ExternalResource {
+public final class AppEngineRule extends ExternalResource
+    implements BeforeEachCallback, AfterEachCallback {
 
   public static final String NEW_REGISTRAR_GAE_USER_ID = "666";
   public static final String THE_REGISTRAR_GAE_USER_ID = "31337";
@@ -93,6 +104,8 @@ public final class AppEngineRule extends ExternalResource {
 
   /** A rule-within-a-rule to provide a temporary folder for AppEngineRule's internal temp files. */
   TemporaryFolder temporaryFolder = new TemporaryFolder();
+  // Sets up a SQL database when running on JUnit 5.
+  JpaIntegrationWithCoverageExtension jpaIntegrationWithCoverageExtension = null;
 
   private boolean withDatastoreAndCloudSql;
   private boolean withLocalModules;
@@ -257,14 +270,38 @@ public final class AppEngineRule extends ExternalResource {
         .build();
   }
 
+  /** Called before every test method. JUnit 5 only. */
+  @Override
+  public void beforeEach(ExtensionContext context) throws Exception {
+    before();
+    if (withDatastoreAndCloudSql) {
+      JpaTestRules.Builder builder = new JpaTestRules.Builder();
+      if (clock != null) {
+        builder.withClock(clock);
+      }
+      jpaIntegrationWithCoverageExtension = builder.buildIntegrationWithCoverageExtension();
+      jpaIntegrationWithCoverageExtension.beforeEach(context);
+    }
+  }
+
+  /** Called after each test method. JUnit 5 only. */
+  @Override
+  public void afterEach(ExtensionContext context) throws Exception {
+    if (withDatastoreAndCloudSql) {
+      checkState(
+          jpaIntegrationWithCoverageExtension != null, "Null jpaIntegrationWithCoverageExtension");
+      jpaIntegrationWithCoverageExtension.afterEach(context);
+    }
+    after();
+  }
+
   /**
    * Hack to make sure AppEngineRule is always wrapped in a {@link JpaIntegrationWithCoverageRule}.
+   * JUnit 4 only.
    */
   // Note: Even with @EnableRuleMigrationSupport, JUnit5 runner does not call this method.
-  // Note 2: Do not migrate any members of SqlIntegrationTestSuite to JUnit5 before
-  // calls to JpaIntegrationWithCoverageRule can be made elsewhere.
-  // TODO(weiminyu): make JpaIntegrationWithCoverageRule implement ExternaResource and invoke it in
-  // before() and after(), then drop this method.
+  // Note 2: Do not migrate members of SqlIntegrationTestSuite to JUnit5 individually.
+  // TODO(weiminyu): migrate SqlIntegrationTestSuite in one go.
   @Override
   public Statement apply(Statement base, Description description) {
     Statement statement = base;