Add unit tests for FileHelper.sanitizeFilename()

src/com/fsck/k9/helper/FileHelper.java

@@ -12,6 +12,7 @@ import com.fsck.k9.K9;
 
 
 public class FileHelper {
+
     /**
      * Regular expression that represents characters we won't allow in file names.
      *
@@ -27,7 +28,7 @@ public class FileHelper {
      *
      * @see #sanitizeFilename(String)
      */
-    private static final String INVALID_CHARACTERS = "[^\\w !#$%&'()\\-@\\^`{}~.,]+";
+    private static final String INVALID_CHARACTERS = "[^\\w !#$%&'()\\-@\\^`{}~.,]";
 
     /**
      * Invalid characters in a file name are replaced by this character.

tests/src/com/fsck/k9/helper/FileHelperTest.java

@@ -0,0 +1,32 @@
+package com.fsck.k9.helper;
+
+import junit.framework.TestCase;
+
+import java.lang.String;
+
+public class FileHelperTest extends TestCase {
+
+    public void testSanitize1() {
+        checkSanitization(".._bla_", "../bla_");
+    }
+
+    public void testSanitize2() {
+        checkSanitization("_etc_bla", "/etc/bla");
+    }
+
+    public void testSanitize3() {
+        checkSanitization("_пPп", "+пPп");
+    }
+
+    public void testSanitize4() {
+        checkSanitization(".東京_!", ".東京?!");
+    }
+
+    public void testSanitize5() {
+        checkSanitization("Plan 9", "Plan 9");
+    }
+
+    private void checkSanitization(String expected, String actual) {
+        assertEquals(expected, FileHelper.sanitizeFilename(actual));
+    }
+}