diff --git a/core-java-modules/core-java-os-2/src/test/java/com/baeldung/java9/process/ProcessWaitTest.java b/core-java-modules/core-java-os-2/src/test/java/com/baeldung/java9/process/ProcessWaitTest.java
new file mode 100644
index 000000000000..e1475960108f
--- /dev/null
+++ b/core-java-modules/core-java-os-2/src/test/java/com/baeldung/java9/process/ProcessWaitTest.java
@@ -0,0 +1,25 @@
+package com.baeldung.java9.process;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class ProcessWaitTest {
+
+    @Test
+    void givenAProcess_whenUsingWaitFor_thenNoExceptionThrown() {
+        // Code that interacts with a process should not throw IllegalMonitorStateException.
+        assertDoesNotThrow(() -> {
+            Process process = new ProcessBuilder("notepad.exe").start();
+            int exitCode = process.waitFor();
+        });
+    }
+
+    @Test
+    void givenAProcess_whenUsingWaitWithoutSynchronization_thenExceptionThrown() {
+        assertThrows(IllegalMonitorStateException.class, () -> {
+            Process process = new ProcessBuilder("notepad.exe").start();
+            process.wait();
+        });
+    }
+}
diff --git a/core-java-modules/core-java-string-apis-2/src/test/java/com/baeldung/stringformat/StringFormatUnitTest.java b/core-java-modules/core-java-string-apis-2/src/test/java/com/baeldung/stringformat/StringFormatUnitTest.java
index 16cf87a26ccd..8a86f2b51d56 100644
--- a/core-java-modules/core-java-string-apis-2/src/test/java/com/baeldung/stringformat/StringFormatUnitTest.java
+++ b/core-java-modules/core-java-string-apis-2/src/test/java/com/baeldung/stringformat/StringFormatUnitTest.java
@@ -103,4 +103,16 @@ public void whenCurrencyFormatWithLocales_thenCorrect() {
         String frenchFormatted = frenchCurrencyFormat.format(1000);
         assertEquals("1 000,00 €", frenchFormatted);
     }
+
+    private String padIntegerWithZeros(int number, int width) {
+       
+        return String.format("%0" + width + "d", number);
+    }
+
+    @Test
+    public void givenAnInteger_whenPaddingWithZeros_thanIntegerGetsPadded() {
+       
+        assertEquals("00000001", padIntegerWithZeros(1, 8));
+        assertEquals("-0000001", padIntegerWithZeros(-1, 8));
+    }
 }