Add new tests in FileFilterTest and LazyErrorMessageTest

Two new tests were added. In FileFilterTest.java, a test for listDirectories_variable and mapForEach was added to validate functionalities. Meanwhile, in LazyErrorMessageTest.java, a Logger was introduced to generate a fine log message during assertion tests.

src/test/java/lambdas/FileFilterTest.java

@@ -4,6 +4,7 @@
 
 import java.io.File;
 import java.io.FileFilter;
+import java.util.Map;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -53,4 +54,20 @@ void listDirectories_blockLambda() {
                 .isNotEmpty()
                 .hasSize(14);
     }
+
+    @Test
+    void listDirectories_variable() {
+        FileFilter filter = (File pathname) -> pathname.isDirectory();
+        File[] directories = root.listFiles(filter);
+        assertThat(directories)
+                .isNotNull()
+                .isNotEmpty()
+                .hasSize(14);
+    }
+
+    @Test
+    void mapForEach() {
+        Map.of(1, "one", 2, "two", 3, "three")
+                .forEach((key, value) -> System.out.println(key + " -> " + value));
+    }
 }

src/test/java/lambdas/LazyErrorMessageTest.java

@@ -2,9 +2,17 @@
 
 import org.junit.jupiter.api.Test;
 
+import java.util.logging.Logger;
+
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 public class LazyErrorMessageTest {
+    private final Logger log = Logger.getLogger(getClass().getName());
+
+    private String getLogMessage() {
+        System.out.println("Generating log message...");
+        return "log message";
+    }
 
     private String getErrorMessage() {
         System.out.println("Generating error message...");
@@ -14,12 +22,14 @@ private String getErrorMessage() {
     @Test
     void assertArgIsTrue() {
         boolean x = true;
+        log.fine(getLogMessage());
         assertTrue(x, getErrorMessage()); // 2nd arg is a String
     }
 
     @Test
     void assertArgIsTrue_lazyErrorMessage() {
         boolean x = true;
+        log.fine(() -> getLogMessage());
         assertTrue(x, () -> getErrorMessage());  // 2nd arg is a Supplier<String>
     }
 }