Fixes for issue junit-team#342

src/main/java/org/junit/rules/TemporaryFolder.java

@@ -39,10 +39,10 @@ protected void after() {
 
 	// testing purposes only
 	/**
-	 * for testing purposes only.  Do not use.
+	 * for testing purposes only. Do not use.
 	 */
 	public void create() throws IOException {
-		folder= newFolder();
+		folder= createTemporaryFolderIn(null);
 	}
 
 	/**
@@ -58,27 +58,31 @@ public File newFile(String fileName) throws IOException {
 	 * Returns a new fresh file with a random name under the temporary folder.
 	 */
 	public File newFile() throws IOException {
-		return File.createTempFile("junit", null, folder);
+		return File.createTempFile("junit", null, getRoot());
 	}
 
 	/**
-	 * Returns a new fresh folder with the given name under the temporary folder.
+	 * Returns a new fresh folder with the given name under the temporary
+	 * folder.
 	 */
 	public File newFolder(String... folderNames) {
-		File file = getRoot();
+		File file= getRoot();
 		for (String folderName : folderNames) {
-			file = new File(file, folderName);
+			file= new File(file, folderName);
 			file.mkdir();
 		}
 		return file;
 	}
 
 	/**
-	 * Returns a new fresh folder with a random name under the temporary
-	 * folder.
+	 * Returns a new fresh folder with a random name under the temporary folder.
 	 */
 	public File newFolder() throws IOException {
-		File createdFolder= File.createTempFile("junit", "", folder);
+		return createTemporaryFolderIn(getRoot());
+	}
+
+	private File createTemporaryFolderIn(File parentFolder) throws IOException {
+		File createdFolder= File.createTempFile("junit", "", parentFolder);
 		createdFolder.delete();
 		createdFolder.mkdir();
 		return createdFolder;
@@ -89,18 +93,19 @@ public File newFolder() throws IOException {
 	 */
 	public File getRoot() {
 		if (folder == null) {
-			throw new IllegalStateException("the temporary folder has not yet been created");
+			throw new IllegalStateException(
+					"the temporary folder has not yet been created");
 		}
 		return folder;
 	}
 
 	/**
-	 * Delete all files and folders under the temporary folder.
-	 * Usually not called directly, since it is automatically applied
-	 * by the {@link Rule}
+	 * Delete all files and folders under the temporary folder. Usually not
+	 * called directly, since it is automatically applied by the {@link Rule}
 	 */
 	public void delete() {
-		recursiveDelete(folder);
+		if (folder != null)
+			recursiveDelete(folder);
 	}
 
 	private void recursiveDelete(File file) {

src/test/java/org/junit/tests/experimental/rules/TemporaryFolderUsageTest.java

@@ -0,0 +1,142 @@
+package org.junit.tests.experimental.rules;
+
+import static org.junit.Assert.*;
+import static org.hamcrest.CoreMatchers.*;
+
+import java.io.File;
+import java.io.IOException;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+/**
+ * <tt>TemporaryFolderUsageTest</tt> provides tests for API usage correctness
+ * and ensure implementation symmetry of public methods against a root folder.
+ */
+public class TemporaryFolderUsageTest {
+
+	private TemporaryFolder tempFolder;
+
+	@Before
+	public void setUp() {
+		tempFolder= new TemporaryFolder();
+	}
+
+	@After
+	public void tearDown() {
+		tempFolder.delete();
+	}
+
+	@Test(expected= IllegalStateException.class)
+	public void getRootShouldThrowIllegalStateExceptionIfCreateWasNotInvoked() {
+		new TemporaryFolder().getRoot();
+	}
+
+	@Test(expected= IllegalStateException.class)
+	public void newFileThrowsIllegalStateExceptionIfCreateWasNotInvoked()
+			throws IOException {
+		new TemporaryFolder().newFile();
+	}
+
+	@Test(expected= IllegalStateException.class)
+	public void newFileWithGivenNameThrowsIllegalStateExceptionIfCreateWasNotInvoked()
+			throws IOException {
+		new TemporaryFolder().newFile("MyFile.txt");
+	}
+
+	@Test(expected= IllegalStateException.class)
+	public void newFolderThrowsIllegalStateExceptionIfCreateWasNotInvoked()
+			throws IOException {
+		new TemporaryFolder().newFolder();
+	}
+
+	@Test(expected= IllegalStateException.class)
+	public void newFolderWithGivenPathThrowsIllegalStateExceptionIfCreateWasNotInvoked() {
+		new TemporaryFolder().newFolder("level1", "leve2", "leve3");
+	}
+
+	@Test
+	public void createInitializesRootFolder() throws IOException {
+		tempFolder.create();
+		assertFileExists("Root folder", tempFolder.getRoot());
+	}
+
+	@Test
+	public void deleteShouldDoNothingIfRootFolderWasNotInitialized() {
+		tempFolder.delete();
+	}
+
+	@Test
+	public void deleteRemovesRootFolder() throws IOException {
+		tempFolder.create();
+		tempFolder.delete();
+		assertFileDoesNotExists("Root folder", tempFolder.getRoot());
+	}
+
+	private void assertFileDoesNotExists(String msg, File file) {
+		assertThat(msg + ": is null", file, is(notNullValue()));
+		assertThat(msg + ": still exists", file.exists(), is(false));
+	}
+
+	private void assertFileExists(String msg, File file) {
+		assertThat(msg + ": is null", file, is(notNullValue()));
+		assertThat(msg + ": does not exist", file.exists(), is(true));
+	}
+
+	@Test
+	public void newRandomFileIsCreatedUnderRootFolder() throws IOException {
+		tempFolder.create();
+
+		File f= tempFolder.newFile();
+		assertFileExists("Random file", f);
+		assertFileCreatedUnderRootFolder("Random file", f);
+	}
+
+	@Test
+	public void newNamedFileIsCreatedUnderRootFolder() throws IOException {
+		final String fileName= "SampleFile.txt";
+		tempFolder.create();
+
+		File f= tempFolder.newFile(fileName);
+
+		assertFileExists("Named file", f);
+		assertFileCreatedUnderRootFolder("Named file", f);
+		assertThat("file name", f.getName(), equalTo(fileName));
+	}
+
+	private void assertFileCreatedUnderRootFolder(String msg, File f) {
+		assertParentFolderForFileIs(msg, f, tempFolder.getRoot());
+	}
+
+	private void assertParentFolderForFileIs(String msg, File f,
+			File parentFolder) {
+		assertThat(msg + ": not under root", f.getParentFile(),
+				is(parentFolder));
+	}
+
+	@Test
+	public void newRandomFolderIsCreatedUnderRootFolder() throws IOException {
+		tempFolder.create();
+
+		File f= tempFolder.newFolder();
+		assertFileExists("Random folder", f);
+		assertFileCreatedUnderRootFolder("Random folder", f);
+	}
+
+	@Test
+	public void newNestedFoldersCreatedUnderRootFolder() throws IOException {
+		tempFolder.create();
+
+		File f= tempFolder.newFolder("top", "middle", "bottom");
+		assertFileExists("Nested folder", f);
+		assertParentFolderForFileIs("bottom", f, new File(tempFolder.getRoot(),
+				"top/middle"));
+		assertParentFolderForFileIs("middle", f.getParentFile(), new File(
+				tempFolder.getRoot(), "top"));
+		assertFileCreatedUnderRootFolder("top", f.getParentFile()
+				.getParentFile());
+	}
+
+}