Throw exception with helpful message if annotated field is not public…

… (fixes issue junit-team#260).

src/main/java/org/junit/runners/model/TestClass.java

@@ -1,5 +1,6 @@
 package org.junit.runners.model;
 
+import static java.lang.reflect.Modifier.isPublic;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
@@ -138,16 +139,25 @@ public Annotation[] getAnnotations() {
 	public <T> List<T> getAnnotatedFieldValues(Object test,
 			Class<? extends Annotation> annotationClass, Class<T> valueClass) {
 		List<T> results= new ArrayList<T>();
-		for (FrameworkField each : getAnnotatedFields(annotationClass)) {
+		for (FrameworkField field : getAnnotatedFields(annotationClass)) {
+			assertFieldIsPublic(field);
 			try {
-				Object fieldValue= each.get(test);
+				Object fieldValue= field.get(test);
 				if (valueClass.isInstance(fieldValue))
 					results.add(valueClass.cast(fieldValue));
 			} catch (IllegalAccessException e) {
 				throw new RuntimeException(
-						"How did getFields return a field we couldn't access?");
+						"How did getFields return a field we couldn't access?", e);
 			}
 		}
 		return results;
 	}
+
+	public void assertFieldIsPublic(FrameworkField frameworkField) {
+		Field field= frameworkField.getField();
+		int modifiers= field.getModifiers();
+		if (!isPublic(modifiers))
+			throw new IllegalArgumentException(
+					"The " + field.getType().getSimpleName() + " '" + field.getName() + "' is not public.");
+	}
 }

src/test/java/org/junit/tests/running/classes/TestClassTest.java

@@ -1,5 +1,6 @@
 package org.junit.tests.running.classes;
 
+import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.is;
 import static org.junit.Assert.assertThat;
 import org.junit.After;
@@ -9,10 +10,14 @@
 import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.junit.rules.TestRule;
 import org.junit.runners.model.TestClass;
 
 public class TestClassTest {
+	@Rule
+	public ExpectedException expectedException = ExpectedException.none();
+
 	public static class TwoConstructors {
 		public TwoConstructors() {
 		}
@@ -78,9 +83,25 @@ public static class SubclassWithField extends SuperclassWithField {
 		public TestRule x;
 	}
 
+	public static class TestWithProtectedTestRule {
+		@Rule
+		protected TestRule x;
+
+		@Test
+		public void test() {
+		}
+	}
+
 	@Test
 	public void fieldsOnSubclassesShadowSuperclasses() {
 		assertThat(new TestClass(SubclassWithField.class).getAnnotatedFields(
 				Rule.class).size(), is(1));
 	}
+
+	@Test
+	public void shouldThrowExcpetionWithHelpfulMessageForProtectedFields() {
+		expectedException.expectMessage(equalTo("The TestRule 'x' is not public."));
+		TestClass testClass = new TestClass(TestWithProtectedTestRule.class);
+		testClass.getAnnotatedFieldValues(testClass, Rule.class, TestRule.class);
+	}
 }