New junit parameter provider from static fields. (#6232)

hapi-fhir-test-utilities/src/main/java/ca/uhn/test/junit/JunitFieldParameterProviderExtension.java

@@ -0,0 +1,92 @@
+package ca.uhn.test.junit;
+
+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.platform.commons.util.ExceptionUtils;
+import org.junit.platform.commons.util.ReflectionUtils;
+
+import java.lang.reflect.Field;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.function.Predicate;
+
+import static org.junit.platform.commons.util.AnnotationUtils.findAnnotatedFields;
+import static org.junit.platform.commons.util.ReflectionUtils.makeAccessible;
+
+/**
+ * Register any field annotated with @{@link JunitFieldProvider} as a parameter provider, matching parameters by type.
+ * Can also be used directly via @RegisterExtension, using values passed to the constructor.
+ */
+public class JunitFieldParameterProviderExtension implements BeforeAllCallback, BeforeEachCallback, ParameterResolver {
+
+	Set<Object> myValues = new HashSet<>();
+
+	/**
+	 * Junit constructor for @{@link org.junit.jupiter.api.extension.ExtendWith}
+	 */
+	public JunitFieldParameterProviderExtension() {}
+
+	/**
+	 * Used for explicit registration.
+	 * @param theValues the values to register as provided junit parameters.
+	 */
+	public JunitFieldParameterProviderExtension(Object ...theValues) {
+		Collections.addAll(myValues, theValues);
+	}
+
+
+	/**
+	 * Do we have a value matching the parameter type?
+	 */
+	@Override
+	public boolean supportsParameter(ParameterContext parameterContext, ExtensionContext extensionContext) throws ParameterResolutionException {
+		Class<?> paramType = parameterContext.getParameter().getType();
+		return myValues.stream().anyMatch(v->paramType.isAssignableFrom(v.getClass()));
+	}
+
+	/**
+	 * Find the first value matching the parameter type.
+	 */
+	@Override
+	public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext) throws ParameterResolutionException {
+		Class<?> paramType = parameterContext.getParameter().getType();
+		return myValues.stream().filter(v->paramType.isAssignableFrom(v.getClass())).findAny().orElseThrow();
+	}
+
+	/**
+	 * Collect all statics annotated with @JunitFieldProvider.
+	 */
+	@Override
+	public void beforeAll(ExtensionContext context) throws Exception {
+		collectFields(null, context.getRequiredTestClass(), ReflectionUtils::isStatic);
+	}
+
+	/**
+	 * Collect any instance fields annotated with @JunitFieldProvider.
+	 */
+	@Override
+	public void beforeEach(ExtensionContext context) {
+		context.getRequiredTestInstances().getAllInstances() //
+			.forEach(instance -> collectFields(instance, instance.getClass(), ReflectionUtils::isStatic));
+	}
+
+	private void collectFields(Object testInstance, Class<?> testClass,
+							   Predicate<Field> predicate) {
+
+		findAnnotatedFields(testClass, JunitFieldProvider.class, predicate).forEach(field -> {
+			try {
+				makeAccessible(field);
+				myValues.add(field.get(testInstance));
+			}
+			catch (Exception t) {
+				ExceptionUtils.throwAsUncheckedException(t);
+			}
+		});
+	}
+
+}

hapi-fhir-test-utilities/src/main/java/ca/uhn/test/junit/JunitFieldProvider.java

@@ -0,0 +1,18 @@
+package ca.uhn.test.junit;
+
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Field annotation to register a value for use in JUnit 5 parameter resolution.
+ */
+@Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD})
+@Retention(RetentionPolicy.RUNTIME)
+@ExtendWith(JunitFieldParameterProviderExtension.class)
+public @interface JunitFieldProvider {
+
+}

hapi-fhir-test-utilities/src/main/java/ca/uhn/test/junit/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * Junit helpers
+ */
+package ca.uhn.test.junit;

hapi-fhir-test-utilities/src/test/java/ca/uhn/test/junit/JunitFieldParameterProviderExtensionTest.java

@@ -0,0 +1,46 @@
+package ca.uhn.test.junit;
+
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class JunitFieldParameterProviderExtensionTest {
+	/** Verify statics annotated with @{@link JunitFieldProvider} are available to static junit methods. */
+	@Nested
+	class AnnotationRegistration implements IParameterizedTestTemplate {
+		@JunitFieldProvider
+		static final CaseSupplyingFixture ourFixture = new CaseSupplyingFixture();
+	}
+	/** Verify explicit registration of the extension.*/
+	@Nested
+	class ExplicitRegistration implements IParameterizedTestTemplate {
+		static final CaseSupplyingFixture ourFixture = new CaseSupplyingFixture();
+		@RegisterExtension
+		static final JunitFieldParameterProviderExtension ourExtension = new JunitFieldParameterProviderExtension(ourFixture);
+	}
+
+	static class CaseSupplyingFixture {
+		public List<Integer> getCases() {
+			return List.of(1,2,3);
+		}
+	}
+	interface IParameterizedTestTemplate {
+		@ParameterizedTest
+		// intellij complains when a static source requires params
+		@SuppressWarnings("JUnitMalformedDeclaration")
+		@MethodSource("testCaseSource")
+		default void testStaticFactoryBound(int theTestCase) {
+			// given
+			assertTrue(theTestCase > 0);
+		}
+
+		static List<Integer> testCaseSource(CaseSupplyingFixture theFixture) {
+			return theFixture.getCases();
+		}
+	}
+}