Add unit tests for lazy vs eager message evaluation

Introduce `LazyMessageTest` to compare eager and lazy message evaluation in assertions and logging. This provides better insights into optimization and ensures correct behavior when using lambda expressions for deferred execution.

src/test/java/lambdas/LazyMessageTest.java

@@ -0,0 +1,35 @@
+package lambdas;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.logging.Logger;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class LazyMessageTest {
+    private final Logger logger = Logger.getLogger(LazyMessageTest.class.getName());
+
+    private String getErrorMessage() {
+        System.out.println("Getting error message");
+        return "Error message";
+    }
+
+    private String getLogMessage() {
+        System.out.println("Getting log message");
+        return "Log message";
+    }
+
+    @Test
+    void eagerMessage() {
+        boolean x = true;
+        assertTrue(x, getErrorMessage());
+        logger.fine(getLogMessage());
+    }
+
+    @Test
+    void lazyMessage() {
+        boolean x = true;
+        assertTrue(x, () -> getErrorMessage());
+        logger.fine(() -> getLogMessage());
+    }
+}