Assistant: 
User: 
    Please analyze the following code file and determine whether it belongs to any of the provided modules based on the listed module descriptions.
    Note that the provided list of modules may not be exhaustive, and some files may not belong to any of the modules. 
    If the code belongs to a module, Only output the module name, without any explanation or additional information; otherwise, return 'None' if it does not belong to any module.

    Modules : {
        "UI": "Handles the front-end user interface, consisting of HTML, CSS, and JavaScript files generated by the Angular framework. It processes user requests and interacts with the server using AJAX for data retrieval and client-side interactions."
"Test Driver": "Facilitates automated regression testing and handles transmission of test data in JSON format. It performs Java testing using TestNG and JavaScript unit-testing with Jest. It also sets up a simulated web server for servlet-level tests and automates end-to-end testing using Selenium Java."
"Logic": "Manages the business logic of TEAMMATES, including handling relationships between entities, managing transactions, input value sanitization, access control rights, and interfacing with GAE-provided or third-party APIs."
"Storage": "Performs CRUD operations on data entities, validation of data, and abstraction of GQL queries, hiding the complexities of datastore from the Logic component."
"Common": "Contains utility classes, custom exceptions, and data transfer objects used across the entire application for easy consolidation and transfer of structured data."
"E2E": "Handles end-to-end testing and load & performance testing, providing helpers, abstractions of browser pages, and test cases for E2E tests and L&P tests."
"Client": "Contains scripts for administrative tasks, such as migrating data to a new schema and calculating statistics. This module connects directly to the application back-end for administrative purposes."
    }

    Code: package teammates.common.util; /** * SUT: {@link StringHelper}. */ public class StringHelperTest extends BaseTestCase { @Test public void testIsEmpty() { assertTrue(StringHelper.isEmpty(null)); assertTrue(StringHelper.isEmpty("")); assertFalse(StringHelper.isEmpty("test")); assertFalse(StringHelper.isEmpty(" ")); } @Test public void testGenerateStringOfLength() { assertEquals("sssss", StringHelper.generateStringOfLength(5, 's')); assertEquals("", StringHelper.generateStringOfLength(0, 's')); } @Test public void testIsMatching() { assertTrue(StringHelper.isMatching("\u00E0", "à")); assertTrue(StringHelper.isMatching("\u0061\u0300", "à")); assertFalse(StringHelper.isMatching("Héllo", "Hello")); } @Test public void testToString() { List<String> strings = new ArrayList<>(); assertEquals("", StringHelper.toString(strings, "")); assertEquals("", StringHelper.toString(strings, "<br>")); strings.add("aaa"); assertEquals("aaa", StringHelper.toString(strings, "")); assertEquals("aaa", StringHelper.toString(strings, "\n")); assertEquals("aaa", StringHelper.toString(strings, "<br>")); strings.add("bbb"); assertEquals("aaabbb", StringHelper.toString(strings, "")); assertEquals("aaa\nbbb", StringHelper.toString(strings, "\n")); assertEquals("aaa<br>bbb", StringHelper.toString(strings, "<br>")); List<Integer> ints = new ArrayList<>(); ints.add(1); ints.add(44); assertEquals("1\n44", StringHelper.toString(ints, "\n")); } @Test public void testKeyEncryption() throws Exception { String msg = "Test decryption"; String decrptedMsg; decrptedMsg = StringHelper.decrypt(StringHelper.encrypt(msg)); assertEquals(msg, decrptedMsg); } @Test public void testDefaultAesCipherParams() throws Exception { //plaintext is less than 1 block long String plaintextLength124 = StringHelper.generateStringOfLength(31, 'A'); assertEncryptionUsesExpectedDefaultParams(plaintextLength124); //plaintext is equal to 1 block String plaintextLength128 = StringHelper.generateStringOfLength(32, 'A'); assertEncryptionUsesExpectedDefaultParams(plaintextLength128); //plaintext is more than 1 block long String plaintextLength132 = StringHelper.generateStringOfLength(33, 'A'); assertEncryptionUsesExpectedDefaultParams(plaintextLength132); } /** * Verifies that encrypting with and without specifying algorithm parameters produce the same ciphertext. * This ensures parameters being specified for encryption are the same as the defaults. * * @param plaintext the plaintext to encrypt, as a hexadecimal string. */ private static void assertEncryptionUsesExpectedDefaultParams(String plaintext) throws Exception { String actualCiphertext = encryptWithoutSpecifyingAlgorithmParams(plaintext); String expectedCiphertext = StringHelper.encrypt(plaintext); assertEquals(expectedCiphertext, actualCiphertext); } /** * Encrypts plaintext without specifying mode and padding scheme during {@link Cipher} initialization. * * @param plaintext t
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