diff --git a/.gitignore b/.gitignore
index 5dc7abec6a..f78dcd70e1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -107,4 +107,7 @@ spring-boot-modules/spring-boot-properties-3/*.log
 .sdkmanrc
 
 # Localstack
-**/.localstack
\ No newline at end of file
+**/.localstack
+
+#web-modules/ninja
+devDb*.db
\ No newline at end of file
diff --git a/core-java-modules/core-java-security-algorithms/src/test/java/com/baeldung/aes/AESUtilUnitTest.java b/core-java-modules/core-java-security-algorithms/src/test/java/com/baeldung/aes/AESUtilUnitTest.java
index 531c20ca79..04499a4fed 100644
--- a/core-java-modules/core-java-security-algorithms/src/test/java/com/baeldung/aes/AESUtilUnitTest.java
+++ b/core-java-modules/core-java-security-algorithms/src/test/java/com/baeldung/aes/AESUtilUnitTest.java
@@ -48,7 +48,7 @@ class AESUtilUnitTest implements WithAssertions {
         IvParameterSpec ivParameterSpec = AESUtil.generateIv();
         File inputFile = Paths.get("src/test/resources/baeldung.txt")
             .toFile();
-        File encryptedFile = new File("classpath:baeldung.encrypted");
+        File encryptedFile = new File("baeldung.encrypted");
         File decryptedFile = new File("document.decrypted");
 
         // when
@@ -57,8 +57,8 @@ class AESUtilUnitTest implements WithAssertions {
 
         // then
         assertThat(inputFile).hasSameTextualContentAs(decryptedFile);
-        encryptedFile.delete();
-        decryptedFile.delete();
+        encryptedFile.deleteOnExit();
+        decryptedFile.deleteOnExit();
     }
 
     @Test
diff --git a/patterns-modules/design-patterns-singleton/src/test/java/com/baeldung/serializable_singleton/EnumSingletonUnitTest.java b/patterns-modules/design-patterns-singleton/src/test/java/com/baeldung/serializable_singleton/EnumSingletonUnitTest.java
index e0a098056a..7fdcb20850 100644
--- a/patterns-modules/design-patterns-singleton/src/test/java/com/baeldung/serializable_singleton/EnumSingletonUnitTest.java
+++ b/patterns-modules/design-patterns-singleton/src/test/java/com/baeldung/serializable_singleton/EnumSingletonUnitTest.java
@@ -1,8 +1,10 @@
 package com.baeldung.serializable_singleton;
 
+import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.Test;
 import static org.junit.jupiter.api.Assertions.*;
 
+import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.ObjectInputStream;
@@ -10,8 +12,10 @@ import java.io.ObjectOutputStream;
 
 // Unit test for the EnumSingleton class.
 public class EnumSingletonUnitTest {
-    
-	// Checks that when an EnumSingleton instance is serialized
+
+    private static final String ENUM_SINGLETON_TEST_TXT = "enum_singleton_test.txt";
+
+    // Checks that when an EnumSingleton instance is serialized
     // and then deserialized, its state is preserved.
     @Test
     public void givenEnumSingleton_whenSerializedAndDeserialized_thenStatePreserved() {
@@ -19,11 +23,10 @@ public class EnumSingletonUnitTest {
 
         es1.setState("State One");
 
-        try (
-        FileOutputStream fos = new FileOutputStream("enum_singleton_test.txt");
-        ObjectOutputStream oos = new ObjectOutputStream(fos);
-        FileInputStream fis = new FileInputStream("enum_singleton_test.txt");
-        ObjectInputStream ois = new ObjectInputStream(fis)) {
+        try (FileOutputStream fos = new FileOutputStream(ENUM_SINGLETON_TEST_TXT);
+             ObjectOutputStream oos = new ObjectOutputStream(fos);
+             FileInputStream fis = new FileInputStream(ENUM_SINGLETON_TEST_TXT);
+             ObjectInputStream ois = new ObjectInputStream(fis)) {
             
             // Serializing.
             oos.writeObject(es1);
@@ -46,11 +49,10 @@ public class EnumSingletonUnitTest {
     public void givenEnumSingleton_whenSerializedAndDeserialized_thenOneInstance() {
         EnumSingleton es1 = EnumSingleton.getInstance();
 
-        try (
-        FileOutputStream fos = new FileOutputStream("enum_singleton_test.txt");
-        ObjectOutputStream oos = new ObjectOutputStream(fos);
-        FileInputStream fis = new FileInputStream("enum_singleton_test.txt");
-        ObjectInputStream ois = new ObjectInputStream(fis)) {
+        try (FileOutputStream fos = new FileOutputStream(ENUM_SINGLETON_TEST_TXT);
+             ObjectOutputStream oos = new ObjectOutputStream(fos);
+             FileInputStream fis = new FileInputStream(ENUM_SINGLETON_TEST_TXT);
+             ObjectInputStream ois = new ObjectInputStream(fis)) {
 
             // Serializing.
             oos.writeObject(es1);
@@ -66,4 +68,12 @@ public class EnumSingletonUnitTest {
             System.out.println(e);
         }
     }
+
+    @AfterAll
+    public static void cleanUp() {
+        final File removeFile = new File(ENUM_SINGLETON_TEST_TXT);
+        if (removeFile.exists()) {
+            removeFile.deleteOnExit();
+        }
+    }
 }
diff --git a/patterns-modules/design-patterns-singleton/src/test/java/com/baeldung/serializable_singleton/SingletonUnitTest.java b/patterns-modules/design-patterns-singleton/src/test/java/com/baeldung/serializable_singleton/SingletonUnitTest.java
index cc26eb6995..a46288cc8f 100644
--- a/patterns-modules/design-patterns-singleton/src/test/java/com/baeldung/serializable_singleton/SingletonUnitTest.java
+++ b/patterns-modules/design-patterns-singleton/src/test/java/com/baeldung/serializable_singleton/SingletonUnitTest.java
@@ -1,8 +1,10 @@
 package com.baeldung.serializable_singleton;
 
+import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.Test;
 import static org.junit.jupiter.api.Assertions.*;
 
+import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.ObjectInputStream;
@@ -10,8 +12,10 @@ import java.io.ObjectOutputStream;
 
 // Unit test for the Singleton class.
 public class SingletonUnitTest {
-    
-	// Checks that when a Singleton instance is serialized
+
+    private static final String SINGLETON_TEST_TXT = "singleton_test.txt";
+
+    // Checks that when a Singleton instance is serialized
     // and then deserialized, its state is preserved.
     @Test
     public void givenSingleton_whenSerializedAndDeserialized_thenStatePreserved() {
@@ -19,11 +23,10 @@ public class SingletonUnitTest {
 
         s1.setState("State One");
 
-        try (
-        FileOutputStream fos = new FileOutputStream("singleton_test.txt");
-        ObjectOutputStream oos = new ObjectOutputStream(fos);
-        FileInputStream fis = new FileInputStream("singleton_test.txt");
-        ObjectInputStream ois = new ObjectInputStream(fis)) {
+        try (FileOutputStream fos = new FileOutputStream(SINGLETON_TEST_TXT);
+             ObjectOutputStream oos = new ObjectOutputStream(fos);
+             FileInputStream fis = new FileInputStream(SINGLETON_TEST_TXT);
+             ObjectInputStream ois = new ObjectInputStream(fis)) {
 
             // Serializing.
             oos.writeObject(s1);
@@ -46,11 +49,10 @@ public class SingletonUnitTest {
     public void givenSingleton_whenSerializedAndDeserialized_thenTwoInstances() {
         Singleton s1 = Singleton.getInstance();
 
-        try (
-        FileOutputStream fos = new FileOutputStream("singleton_test.txt");
-        ObjectOutputStream oos = new ObjectOutputStream(fos);
-        FileInputStream fis = new FileInputStream("singleton_test.txt");
-        ObjectInputStream ois = new ObjectInputStream(fis)) {
+        try (FileOutputStream fos = new FileOutputStream(SINGLETON_TEST_TXT);
+             ObjectOutputStream oos = new ObjectOutputStream(fos);
+             FileInputStream fis = new FileInputStream(SINGLETON_TEST_TXT);
+             ObjectInputStream ois = new ObjectInputStream(fis)) {
 
             // Serializing.
             oos.writeObject(s1);
@@ -65,4 +67,12 @@ public class SingletonUnitTest {
             System.out.println(e);
         }
     }
+
+    @AfterAll
+    public static void cleanUp() {
+        final File removeFile = new File(SINGLETON_TEST_TXT);
+        if (removeFile.exists()) {
+            removeFile.deleteOnExit();
+        }
+    }
 }