Implemented random temp file/folder creation

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

@@ -42,9 +42,7 @@ protected void after() {
 	 * for testing purposes only.  Do not use.
 	 */
 	public void create() throws IOException {
-		folder= File.createTempFile("junit", "");
-		folder.delete();
-		folder.mkdir();
+		folder= newFolder();
 	}
 
 	/**
@@ -56,6 +54,13 @@ public File newFile(String fileName) throws IOException {
 		return file;
 	}
 
+	/**
+	 * Returns a new fresh file with a random name under the temporary folder.
+	 */
+	public File newFile() throws IOException {
+		return File.createTempFile("junit", null, folder);
+	}
+
 	/**
 	 * Returns a new fresh folder with the given name under the temporary folder.
 	 */
@@ -68,6 +73,17 @@ public File newFolder(String... folderNames) {
 		return file;
 	}
 
+	/**
+	 * Returns a new fresh folder with a random name under the temporary
+	 * folder.
+	 */
+	public File newFolder() throws IOException {
+		File createdFolder= File.createTempFile("junit", "", folder);
+		createdFolder.delete();
+		createdFolder.mkdir();
+		return createdFolder;
+	}
+
 	/**
 	 * @return the location of this temporary folder.
 	 */

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

@@ -1,36 +1,39 @@
 package org.junit.tests.experimental.rules;
 
+import static org.hamcrest.core.IsNot.not;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.experimental.results.PrintableResult.testResult;
 import static org.junit.experimental.results.ResultMatchers.isSuccessful;
+import static org.junit.internal.matchers.IsCollectionContaining.hasItem;
 
 import java.io.File;
 import java.io.IOException;
+import java.util.Arrays;
 
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 
 public class TempFolderRuleTest {
-	private static File createdFile;
+	private static File[] createdFiles= new File[20];
 
 	public static class HasTempFolder {
 		@Rule
 		public TemporaryFolder folder= new TemporaryFolder();
 
 		@Test
 		public void testUsingTempFolder() throws IOException {
-			createdFile= folder.newFile("myfile.txt");
-			assertTrue(createdFile.exists());
+			createdFiles[0]= folder.newFile("myfile.txt");
+			assertTrue(createdFiles[0].exists());
 		}
 	}
 
 	@Test
 	public void tempFolderIsDeleted() {
 		assertThat(testResult(HasTempFolder.class), isSuccessful());
-		assertFalse(createdFile.exists());
+		assertFalse(createdFiles[0].exists());
 	}
 
 	public static class CreatesSubFolder {
@@ -41,8 +44,8 @@ public static class CreatesSubFolder {
 		public void testUsingTempFolder() throws IOException {
 			String subfolder = "subfolder";
 			String filename = "a.txt";
-			createdFile= folder.newFolder(subfolder);
-			new File(createdFile, filename).createNewFile();
+			createdFiles[0]= folder.newFolder(subfolder);
+			new File(createdFiles[0], filename).createNewFile();
 
 			File expectedFile = new File(folder.getRoot(), join(subfolder, filename));
 
@@ -55,8 +58,8 @@ public void testUsingTempTreeFolders() throws IOException {
 			String anotherfolder = "anotherfolder";
 			String filename = "a.txt";
 
-			createdFile = folder.newFolder(subfolder, anotherfolder);
-			new File(createdFile, filename).createNewFile();
+			createdFiles[0] = folder.newFolder(subfolder, anotherfolder);
+			new File(createdFiles[0], filename).createNewFile();
 
 			File expectedFile = new File(folder.getRoot(), join(subfolder, anotherfolder, filename));
 
@@ -75,7 +78,54 @@ private String join(String... folderNames) {
 	@Test
 	public void subFolderIsDeleted() {
 		assertThat(testResult(CreatesSubFolder.class), isSuccessful());
-		assertFalse(createdFile.exists());
+		assertFalse(createdFiles[0].exists());
+	}
+
+	public static class CreatesRandomSubFolders {
+		@Rule
+		public TemporaryFolder folder= new TemporaryFolder();
+
+		@Test
+		public void testUsingRandomTempFolders() throws IOException {
+			for (int i= 0; i < 20; i++) {
+				File newFolder= folder.newFolder();
+				assertThat(Arrays.asList(createdFiles), not(hasItem(newFolder)));
+				createdFiles[i]= newFolder;
+				new File(newFolder, "a.txt").createNewFile();
+				assertTrue(newFolder.exists());
+			}
+		}
+	}
+
+	@Test
+	public void randomSubFoldersAreDeleted() {
+		assertThat(testResult(CreatesRandomSubFolders.class), isSuccessful());
+		for (File f : createdFiles) {
+			assertFalse(f.exists());
+		}
+	}
+
+	public static class CreatesRandomFiles {
+		@Rule
+		public TemporaryFolder folder= new TemporaryFolder();
+
+		@Test
+		public void testUsingRandomTempFiles() throws IOException {
+			for (int i= 0; i < 20; i++) {
+				File newFile= folder.newFile();
+				assertThat(Arrays.asList(createdFiles), not(hasItem(newFile)));
+				createdFiles[i]= newFile;
+				assertTrue(newFile.exists());
+			}
+		}
+	}
+
+	@Test
+	public void randomFilesAreDeleted() {
+		assertThat(testResult(CreatesRandomFiles.class), isSuccessful());
+		for (File f : createdFiles) {
+			assertFalse(f.exists());
+		}
 	}
 
 	@Test
@@ -88,6 +138,16 @@ public void recursiveDeleteFolderWithOneElement() throws IOException {
 		assertFalse(folder.getRoot().exists());
 	}
 
+	@Test
+	public void recursiveDeleteFolderWithOneRandomElement() throws IOException {
+		TemporaryFolder folder= new TemporaryFolder();
+		folder.create();
+		File file= folder.newFile();
+		folder.delete();
+		assertFalse(file.exists());
+		assertFalse(folder.getRoot().exists());
+	}
+
 	@Test
 	public void recursiveDeleteFolderWithZeroElements() throws IOException {
 		TemporaryFolder folder= new TemporaryFolder();