diff --git a/aws-lambda-java-runtime-interface-client/pom.xml b/aws-lambda-java-runtime-interface-client/pom.xml
index b5ea2721..e84cac0d 100644
--- a/aws-lambda-java-runtime-interface-client/pom.xml
+++ b/aws-lambda-java-runtime-interface-client/pom.xml
@@ -87,6 +87,12 @@
             <version>4.11.0</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-junit-jupiter</artifactId>
+            <version>4.11.0</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>com.squareup.okhttp3</groupId>
             <artifactId>mockwebserver</artifactId>
diff --git a/aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/util/LambdaOutputStreamTest.java b/aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/util/LambdaOutputStreamTest.java
new file mode 100644
index 00000000..30146ea8
--- /dev/null
+++ b/aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/util/LambdaOutputStreamTest.java
@@ -0,0 +1,81 @@
+/*
+Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package com.amazonaws.services.lambda.runtime.api.client.util;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+import static org.mockito.Mockito.*;
+import static org.junit.jupiter.api.Assertions.*;
+
+@ExtendWith(MockitoExtension.class)
+public class LambdaOutputStreamTest {
+
+    @Mock
+    private OutputStream mockInnerStream;
+
+    private LambdaOutputStream lambdaOutputStream;
+
+    @BeforeEach
+    void setUp() {
+        lambdaOutputStream = new LambdaOutputStream(mockInnerStream);
+    }
+
+    @Test
+    void writeSingleByte() throws IOException {
+        int testByte = 65; // 'A'
+        lambdaOutputStream.write(testByte);
+        verify(mockInnerStream).write(new byte[]{(byte) testByte}, 0, 1);
+    }
+
+    @Test
+    void writeByteArray() throws IOException {
+        byte[] testBytes = "test".getBytes();
+        lambdaOutputStream.write(testBytes);
+        verify(mockInnerStream).write(testBytes, 0, testBytes.length);
+    }
+
+    @Test
+    void writeOffsetLength() throws IOException {
+        byte[] testBytes = "test".getBytes();
+        int offset = 1;
+        int length = 2;
+        lambdaOutputStream.write(testBytes, offset, length);
+        verify(mockInnerStream).write(testBytes, offset, length);
+    }
+
+    @Test
+    void throwWriteSingleByte() throws IOException {
+        doThrow(new IOException("Test exception"))
+            .when(mockInnerStream)
+            .write(any(byte[].class), anyInt(), anyInt());
+        assertThrows(IOException.class, () -> lambdaOutputStream.write(65));
+    }
+
+    @Test
+    void throwWriteByteArray() throws IOException {
+        byte[] testBytes = "test".getBytes();
+        doThrow(new IOException("Test exception"))
+            .when(mockInnerStream)
+            .write(any(byte[].class), anyInt(), anyInt());
+        assertThrows(IOException.class, () -> lambdaOutputStream.write(testBytes));
+    }
+
+    @Test
+    void throwWriteOffsetLength() throws IOException {
+        byte[] testBytes = "test".getBytes();
+        doThrow(new IOException("Test exception"))
+            .when(mockInnerStream)
+            .write(any(byte[].class), anyInt(), anyInt());
+        assertThrows(IOException.class, () -> lambdaOutputStream.write(testBytes, 1, 2));
+    }
+}
diff --git a/aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/util/UnsafeUtilTest.java b/aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/util/UnsafeUtilTest.java
new file mode 100644
index 00000000..b1f0592f
--- /dev/null
+++ b/aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/util/UnsafeUtilTest.java
@@ -0,0 +1,56 @@
+/*
+Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package com.amazonaws.services.lambda.runtime.api.client.util;
+
+import org.junit.jupiter.api.Test;
+import java.lang.reflect.Field;
+import static org.junit.jupiter.api.Assertions.*;
+
+public class UnsafeUtilTest {
+
+    @Test
+    void testTheUnsafeIsInitialized() {
+        assertNotNull(UnsafeUtil.TheUnsafe);
+    }
+
+    @Test
+    void testThrowException() {
+        Exception testException = new Exception("Test exception");
+        
+        try {
+            UnsafeUtil.throwException(testException);
+            fail("Should have thrown an exception");
+        } catch (Throwable e) {
+            assertEquals("Test exception", e.getMessage());
+            assertSame(testException, e);
+        }
+    }
+
+    @Test
+    void testDisableIllegalAccessWarning() {
+        assertDoesNotThrow(() -> UnsafeUtil.disableIllegalAccessWarning());
+        try {
+            Class<?> illegalAccessLoggerClass = Class.forName("jdk.internal.module.IllegalAccessLogger");
+            Field loggerField = illegalAccessLoggerClass.getDeclaredField("logger");
+            loggerField.setAccessible(true);
+            Object loggerValue = loggerField.get(null);
+            assertNull(loggerValue);
+        } catch (ClassNotFoundException e) {
+            assertTrue(true);
+        } catch (NoSuchFieldException e) {
+            assertTrue(true);
+        } catch (Exception e) {
+            fail("Unexpected exception: " + e.getMessage());
+        }
+    }
+
+    @Test
+    void testPrivateConstructor() {
+        assertThrows(IllegalAccessException.class, () -> {
+            UnsafeUtil.class.getDeclaredConstructor().newInstance();
+        });
+    }
+}