* callers. Instead, accept {@link Iterable} and have your method or constructor body pass it to the
 * appropriate {@code copyOf} method itself.
 *
 * <p>Expressing the immutability guarantee directly in the type that user code references is a
 * powerful advantage. Although Java offers certain immutable collection factory methods, such as
 * {@link Collections#singleton(Object)} and <a

        String testString = "abcde";

        // The check method should return the same string instance
        String result = pacString.check(testString);
        assertSame(testString, result, "The check method should return the original string on success.");
    }

    /**
     * Tests the {@link PacUnicodeString#check(String)} method with a null string when the pointer is zero.

    try {
      new NullPointerTester().testMethod(bar, method);
    } catch (AssertionError incorrectError) {
      String errorMessage =
          rootLocaleFormat("Should not have flagged method %s for %s", method.getName(), bar);
      assertWithMessage(errorMessage).that(incorrectError).isNull();
    }
  }

  public void verifyBarFail(Method method, TwoArg bar) {
    try {

}
```

## 🏗️ Architecture & Design Patterns

### Core Design Principles
CoreLib follows a **utility-class pattern** where most functionality is exposed through static methods:

- **Assertion-based validation** - All methods validate inputs using `AssertionUtil.assertArgumentNotNull()` and `AssertionUtil.assertArgumentNotEmpty()`

    for (Method method : getInstanceMethodsToTest(instance.getClass(), minimalVisibility)) {
      testMethod(instance, method);
    }
  }

  ImmutableList<Method> getInstanceMethodsToTest(Class<?> c, Visibility minimalVisibility) {
    ImmutableList.Builder<Method> builder = ImmutableList.builder();
    for (Method method : minimalVisibility.getInstanceMethods(c)) {

    }

    @Test
    @DisplayName("Interface declares no methods or fields")
    void testNoMembers() {
        // Assert
        assertEquals(0, SessionSetupHandler.class.getDeclaredMethods().length, "No methods expected");
        assertEquals(0, SessionSetupHandler.class.getDeclaredFields().length, "No fields expected");

import java.util.concurrent.TimeUnit;

/**
 * Factory methods for {@link ExecutorService} for testing.
 *
 * @author Chris Nokleberg
 * @since 14.0
 */
@GwtIncompatible
public final class TestingExecutors {
  private TestingExecutors() {}

  /**
   * Returns a {@link ScheduledExecutorService} that never executes anything.
   *
   * <p>The {@code shutdownNow} method of the returned executor always returns an empty list despite

    // -----------/
    // - Methods -/
    // -----------/

    /**
     * Method setFileComment.
     *
     * @param fileComment a fileComment object.
     */
    public void setFileComment(String fileComment) {
        this.fileComment = fileComment;
    } // -- void setFileComment( String )

    /**
     * Method write.
     *
     * @param writer a writer object.

    public MetadataXpp3Writer() {
        delegate = new MetadataStaxWriter();
    }

    /**
     * Method setFileComment.
     *
     * @param fileComment a fileComment object.
     */
    public void setFileComment(String fileComment) {
        delegate.setFileComment(fileComment);
    }

    /**
     * Method write.
     *
     * @param writer   a writer object
     * @param metadata a Metadata object

    // we create a test suite containing a test for every FuturesTest test method and we
    // set it as the name of the test.  Then in runTest we can reflectively load and invoke the
    // corresponding method on FuturesTest in the correct classloader.
    TestSuite suite = new TestSuite(AggregateFutureStateFallbackAtomicHelperTest.class.getName());
    for (Method method : FuturesTest.class.getDeclaredMethods()) {