Polish test

Issue: #40

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junit-tests/src/test/java/org/junit/gen5/engine/junit4/JUnit4TestEngineClassSpecificationResolutionTests.java

@@ -11,12 +11,14 @@
 package org.junit.gen5.engine.junit4;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.junit.gen5.api.Assertions.assertEquals;
+import static org.junit.gen5.api.Assertions.*;
 import static org.junit.gen5.engine.TestPlanSpecification.*;
 
+import java.util.Iterator;
+
 import org.junit.Assert;
 import org.junit.gen5.api.Test;
-import org.junit.gen5.engine.EngineAwareTestDescriptor;
+import org.junit.gen5.commons.util.Preconditions;
 import org.junit.gen5.engine.TestDescriptor;
 import org.junit.gen5.engine.TestPlanSpecification;
 
@@ -26,29 +28,41 @@ class JUnit4TestEngineClassSpecificationResolutionTests {
 
 	@Test
 	void resolvesSimpleJUnit4TestClass() {
-		TestPlanSpecification specification = build(forClass(SimpleJUnit4TestCase.class));
-
-		EngineAwareTestDescriptor engineDescriptor = engine.discoverTests(specification);
+		Class<?> testClass = PlainJUnit4TestCaseWithSingleTestWhichFails.class;
+		TestPlanSpecification specification = build(forClass(testClass));
 
-		assertThat(engineDescriptor.getChildren()).hasSize(1);
+		TestDescriptor engineDescriptor = engine.discoverTests(specification);
 
-		TestDescriptor runnerDescriptor = engineDescriptor.getChildren().iterator().next();
-		assertEquals("junit4:" + SimpleJUnit4TestCase.class.getName(), runnerDescriptor.getUniqueId());
-		assertThat(runnerDescriptor.getChildren()).hasSize(1);
+		TestDescriptor runnerDescriptor = getOnlyElement(engineDescriptor.getChildren());
+		assertTrue(runnerDescriptor.isContainer());
+		assertFalse(runnerDescriptor.isTest());
+		assertEquals(testClass.getName(), runnerDescriptor.getDisplayName());
+		assertEquals("junit4:" + testClass.getName(), runnerDescriptor.getUniqueId());
 
-		TestDescriptor childDescriptor = runnerDescriptor.getChildren().iterator().next();
-		assertEquals(
-			"junit4:" + SimpleJUnit4TestCase.class.getName() + "/test(" + SimpleJUnit4TestCase.class.getName() + ")",
+		TestDescriptor childDescriptor = getOnlyElement(runnerDescriptor.getChildren());
+		assertTrue(childDescriptor.isTest());
+		assertFalse(childDescriptor.isContainer());
+		// TODO #40 Get rid of "(className)" suffix?
+		assertEquals("test(" + testClass.getName() + ")", childDescriptor.getDisplayName());
+		assertEquals("junit4:" + testClass.getName() + "/test(" + testClass.getName() + ")",
 			childDescriptor.getUniqueId());
 		assertThat(childDescriptor.getChildren()).isEmpty();
 	}
 
-	public static class SimpleJUnit4TestCase {
+	public static class PlainJUnit4TestCaseWithSingleTestWhichFails {
 
 		@org.junit.Test
 		public void test() {
 			Assert.fail("this test should fail");
 		}
 
 	}
+
+	private static <T> T getOnlyElement(Iterable<T> iterable) {
+		Iterator<T> iterator = iterable.iterator();
+		Preconditions.condition(iterator.hasNext(), () -> "iterable must not be empty: " + iterable);
+		T result = iterator.next();
+		Preconditions.condition(!iterator.hasNext(), () -> "iterable must not contain more than one item: " + iterable);
+		return result;
+	}
 }