Convert Condition to a first-class TestExtension

- Condition now extends TestExtension.
- @conditional has been removed.
- Conditions are now registered via @ExtendWith
- DisabledCondition is now a top-level class within the JUnit 5 Engine.
- DisabledCondition is now registered by default.
- ConditionEvaluator now retrieves Conditions from the execution context.
- Introduced example @SystemProperty support in DisabledTests.

junit5-api/src/main/java/org/junit/gen5/api/Disabled.java

@@ -10,20 +10,11 @@
 
 package org.junit.gen5.api;
 
-import static org.junit.gen5.commons.util.AnnotationUtils.findAnnotation;
-
 import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
-import java.util.Optional;
-import java.util.function.Function;
-
-import org.junit.gen5.api.extension.Condition;
-import org.junit.gen5.api.extension.Conditional;
-import org.junit.gen5.api.extension.TestExecutionContext;
-import org.junit.gen5.commons.util.StringUtils;
 
 /**
  * {@code @Disabled} is used to signal that the annotated test class or
@@ -38,51 +29,11 @@
 @Target({ ElementType.TYPE, ElementType.METHOD })
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
-@Conditional(Disabled.DisabledCondition.class)
 public @interface Disabled {
 
 	/**
 	 * The reason this test is disabled.
 	 */
 	String value() default "";
 
-	static class DisabledCondition implements Condition {
-
-		/**
-		 * Tests are disabled if {@code @Disabled} is either present on the
-		 * test class or on the test method.
-		 */
-		@Override
-		public Result evaluate(TestExecutionContext context) {
-
-			// Class level?
-			Optional<Disabled> disabled = findAnnotation(context.getTestClass(), Disabled.class);
-			Function<TestExecutionContext, String> reasonBuilder = DisabledCondition::buildClassLevelReason;
-
-			// Method level?
-			if (!disabled.isPresent()) {
-				disabled = findAnnotation(context.getTestMethod(), Disabled.class);
-				reasonBuilder = DisabledCondition::buildMethodLevelReason;
-			}
-
-			if (disabled.isPresent()) {
-				String reason = disabled.map(Disabled::value).filter(StringUtils::isNotBlank).orElse(
-					reasonBuilder.apply(context));
-				return Result.disabled(reason);
-			}
-
-			return Result.enabled("@Disabled is not present");
-		}
-
-		private static String buildClassLevelReason(TestExecutionContext context) {
-			return String.format("@Disabled is present on test class [%s]", context.getTestClass().get().getName());
-		}
-
-		private static String buildMethodLevelReason(TestExecutionContext context) {
-			return String.format("@Disabled is present on test method [%s]",
-				context.getTestMethod().get().toGenericString());
-		}
-
-	}
-
 }

junit5-api/src/main/java/org/junit/gen5/api/extension/Condition.java

@@ -16,26 +16,22 @@
 import lombok.ToString;
 
 /**
- * {@code Condition} defines the test extension API for programmatic,
+ * {@code Condition} defines the {@link TestExtension} API for programmatic,
  * <em>conditional test execution</em>.
  *
  * <p>A {@code Condition} is {@linkplain #evaluate evaluated} to determine
  * if a given test (e.g., class or method) should be executed based on the
- * supplied {@link TestExecutionContext}.
+ * supplied {@link TestExecutionContext}. When evaluated at the class level,
+ * a condition applies to all test methods within that class.
  *
- * <p>Implementations must be registered via {@link Conditional @Conditional}
- * and must provide a no-args constructor.
- *
- * <p>When registered at the class level, a {@code Condition} applies to
- * all test methods within that class.
+ * <p>Implementations must provide a no-args constructor.
  *
  * @author Sam Brannen
  * @since 5.0
- * @see Conditional
  * @see org.junit.gen5.api.Disabled
  */
 @FunctionalInterface
-public interface Condition {
+public interface Condition extends TestExtension {
 
 	/**
 	 * Evaluate this condition for the supplied {@link TestExecutionContext}.

junit5-api/src/main/java/org/junit/gen5/api/extension/ExtendWith.java

@@ -25,8 +25,13 @@
  *
  * <h3>Supported Extension APIs</h3>
  * <ul>
+ * <li>{@link Condition}</li>
  * <li>{@link InstancePostProcessor}</li>
  * <li>{@link MethodParameterResolver}</li>
+ * <li>{@link BeforeEachCallbacks}</li>
+ * <li>{@link AfterEachCallbacks}</li>
+ * <li>{@link BeforeAllCallbacks}</li>
+ * <li>{@link AfterAllCallbacks}</li>
  * </ul>
  *
  * @author Sam Brannen

junit5-engine/src/main/java/org/junit/gen5/engine/junit5/execution/ConditionEvaluator.java

@@ -10,70 +10,48 @@
 
 package org.junit.gen5.engine.junit5.execution;
 
-import static org.junit.gen5.commons.util.AnnotationUtils.findAnnotation;
-
-import java.util.Arrays;
-import java.util.Optional;
-
 import org.junit.gen5.api.extension.Condition;
 import org.junit.gen5.api.extension.Condition.Result;
-import org.junit.gen5.api.extension.Conditional;
 import org.junit.gen5.api.extension.TestExecutionContext;
-import org.junit.gen5.commons.util.ReflectionUtils;
 
 /**
- * {@code ConditionEvaluator} evaluates {@link Condition Conditions}
- * configured via {@link Conditional @Conditional}.
+ * {@code ConditionEvaluator} evaluates all {@link Condition Conditions}
+ * registered in a {@link TestExecutionContext}.
  *
  * @author Sam Brannen
  * @since 5.0
- * @see Conditional
  * @see Condition
  */
 class ConditionEvaluator {
 
 	private static final Result ENABLED = Result.enabled("No 'disabled' conditions encountered");
 
 	/**
-	 * Evaluate all {@link Condition Conditions} configured via
-	 * {@link Conditional @Conditional} for the supplied {@link TestExecutionContext}.
+	 * Evaluate all {@link Condition Conditions} registered for the supplied
+	 * {@link TestExecutionContext}.
 	 *
 	 * @param context the current {@code TestExecutionContext}
-	 * @return the first <em>disabled</em> {@code Result}, or an <em>enabled</em>
-	 * {@code Result} if no disabled conditions are encountered.
+	 * @return the first <em>disabled</em> {@code Result}, or a default
+	 * <em>enabled</em> {@code Result} if no disabled conditions are
+	 * encountered.
 	 */
 	Result evaluate(TestExecutionContext context) {
-		Result result = ENABLED;
-
-		// TODO Introduce support for finding *all* @Conditional annotations.
-		Optional<Conditional> classLevelAnno = findAnnotation(context.getTestClass(), Conditional.class);
-
-		// TODO Don't search at the method level if disabled at the class level.
-		Optional<Conditional> methodLevelAnno = findAnnotation(context.getTestMethod(), Conditional.class);
-
-		Conditional conditional = classLevelAnno.orElse(methodLevelAnno.orElse(null));
-
-		if (conditional != null) {
-			// @formatter:off
-			result = Arrays.stream(conditional.value())
-					.map(clazz -> evaluate(context, clazz))
-					.filter(Result::isDisabled)
-					.findFirst()
-					.orElse(ENABLED);
-			// @formatter:on
-		}
-
-		return result;
+		// @formatter:off
+		return context.getExtensions(Condition.class)
+				.map(condition -> evaluate(context, condition))
+				.filter(Result::isDisabled)
+				.findFirst()
+				.orElse(ENABLED);
+		// @formatter:on
 	}
 
-	private Result evaluate(TestExecutionContext context, Class<? extends Condition> conditionClass) {
+	private Result evaluate(TestExecutionContext context, Condition condition) {
 		try {
-			Condition condition = ReflectionUtils.newInstance(conditionClass);
 			return condition.evaluate(context);
 		}
-		catch (Exception e) {
+		catch (Exception ex) {
 			throw new IllegalStateException(
-				String.format("Failed to evaluate condition [%s]", conditionClass.getName()), e);
+				String.format("Failed to evaluate condition [%s]", condition.getClass().getName()), ex);
 		}
 	}
 

junit5-engine/src/main/java/org/junit/gen5/engine/junit5/execution/TestExtensionRegistry.java

@@ -19,6 +19,7 @@
 
 import org.junit.gen5.api.extension.TestExtension;
 import org.junit.gen5.commons.util.ReflectionUtils;
+import org.junit.gen5.engine.junit5.extension.DisabledCondition;
 import org.junit.gen5.engine.junit5.extension.TestNameParameterResolver;
 
 /**
@@ -28,7 +29,7 @@
 public class TestExtensionRegistry {
 
 	private static final List<Class<? extends TestExtension>> defaultExtensionClasses = Collections.unmodifiableList(
-		Arrays.asList(TestNameParameterResolver.class));
+		Arrays.asList(DisabledCondition.class, TestNameParameterResolver.class));
 
 	static List<Class<? extends TestExtension>> getDefaultExtensionClasses() {
 		return defaultExtensionClasses;

junit5-engine/src/main/java/org/junit/gen5/engine/junit5/extension/DisabledCondition.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2015 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v1.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v10.html
+ */
+
+package org.junit.gen5.engine.junit5.extension;
+
+import static org.junit.gen5.commons.util.AnnotationUtils.findAnnotation;
+
+import java.util.Optional;
+
+import org.junit.gen5.api.Disabled;
+import org.junit.gen5.api.extension.Condition;
+import org.junit.gen5.api.extension.TestExecutionContext;
+import org.junit.gen5.commons.util.StringUtils;
+
+/**
+ * {@link Condition} that supports the {@link Disabled @Disabled} annotation.
+ *
+ * @author Sam Brannen
+ * @since 5.0
+ * @see Disabled
+ */
+public class DisabledCondition implements Condition {
+
+	/**
+	 * Tests are disabled if {@code @Disabled} is either present on the
+	 * test class or on the test method.
+	 */
+	@Override
+	public Result evaluate(TestExecutionContext context) {
+
+		// Class level?
+		Optional<Disabled> disabled = findAnnotation(context.getTestClass(), Disabled.class);
+
+		// Method level?
+		if (!disabled.isPresent()) {
+			disabled = findAnnotation(context.getTestMethod(), Disabled.class);
+		}
+
+		if (disabled.isPresent()) {
+			String reason = disabled.map(Disabled::value).filter(StringUtils::isNotBlank).orElse("Test is @Disabled");
+			return Result.disabled(reason);
+		}
+
+		return Result.enabled("@Disabled is not present");
+	}
+
+}

junit5-engine/src/main/java/org/junit/gen5/engine/junit5/extension/TestNameParameterResolver.java

@@ -19,7 +19,7 @@
 import org.junit.gen5.api.extension.TestExecutionContext;
 
 /**
- * {@code MethodParameterResolver} that resolves the name of the currently
+ * {@link MethodParameterResolver} that resolves the name of the currently
  * executing test for {@code String} method parameters annotated with
  * {@link TestName @TestName}.
  *