diff --git a/aws-lambda-java-runtime-interface-client/pom.xml b/aws-lambda-java-runtime-interface-client/pom.xml
index 69692378..df42879b 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>com.squareup.okhttp3</groupId>
+            <artifactId>mockwebserver</artifactId>
+            <version>4.12.0</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
diff --git a/aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/runtimeapi/LambdaRuntimeApiClientImplTest.java b/aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/runtimeapi/LambdaRuntimeApiClientImplTest.java
new file mode 100644
index 00000000..1b6f3136
--- /dev/null
+++ b/aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/runtimeapi/LambdaRuntimeApiClientImplTest.java
@@ -0,0 +1,382 @@
+/*
+Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package com.amazonaws.services.lambda.runtime.api.client.runtimeapi;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.DisabledOnOs;
+import org.junit.jupiter.api.condition.OS;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import com.amazonaws.services.lambda.runtime.api.client.runtimeapi.dto.ErrorRequest;
+import com.amazonaws.services.lambda.runtime.api.client.runtimeapi.dto.StackElement;
+import com.amazonaws.services.lambda.runtime.api.client.runtimeapi.dto.XRayErrorCause;
+import com.amazonaws.services.lambda.runtime.api.client.runtimeapi.dto.XRayException;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.fail;
+import okhttp3.HttpUrl;
+import static java.net.HttpURLConnection.HTTP_ACCEPTED;
+import static java.net.HttpURLConnection.HTTP_OK;
+import static java.net.HttpURLConnection.HTTP_INTERNAL_ERROR;
+import okhttp3.mockwebserver.MockWebServer;
+
+import okhttp3.mockwebserver.MockResponse;
+import okhttp3.mockwebserver.RecordedRequest;
+
+@DisabledOnOs(OS.MAC)
+public class LambdaRuntimeApiClientImplTest {
+
+    MockWebServer mockWebServer;
+    LambdaRuntimeApiClientImpl lambdaRuntimeApiClientImpl;
+
+    String[] errorStackStrace = { "item0", "item1", "item2" };
+    ErrorRequest errorRequest = new ErrorRequest("testErrorMessage", "testErrorType", errorStackStrace);
+
+    String requestId = "1234";
+
+    @BeforeEach
+    void setUp() {
+        mockWebServer = new MockWebServer();
+        String hostnamePort = getHostnamePort();
+        lambdaRuntimeApiClientImpl = new LambdaRuntimeApiClientImpl(hostnamePort);
+    }
+
+    @Test
+    public void reportInitErrorTest() {
+        try {
+            RapidErrorType rapidErrorType = RapidErrorType.AfterRestoreError;
+
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(HTTP_ACCEPTED);
+            mockWebServer.enqueue(mockResponse);
+
+            LambdaError lambdaError = new LambdaError(errorRequest, rapidErrorType);
+            lambdaRuntimeApiClientImpl.reportInitError(lambdaError);
+            RecordedRequest recordedRequest = mockWebServer.takeRequest();
+            HttpUrl actualUrl = recordedRequest.getRequestUrl();
+            String expectedUrl = "http://" + getHostnamePort() + "/2018-06-01/runtime/init/error";
+            assertEquals(expectedUrl, actualUrl.toString());
+
+            String userAgentHeader = recordedRequest.getHeader("User-Agent");
+            assertTrue(userAgentHeader.startsWith("aws-lambda-java/"));
+
+            String lambdaRuntimeErrorTypeHeader = recordedRequest.getHeader("Lambda-Runtime-Function-Error-Type");
+            assertEquals("Runtime.AfterRestoreError", lambdaRuntimeErrorTypeHeader);
+
+            String actualBody = recordedRequest.getBody().readUtf8();
+            assertEquals("{\"errorMessage\":\"testErrorMessage\",\"errorType\":\"testErrorType\",\"stackTrace\":[\"item0\",\"item1\",\"item2\"]}", actualBody);
+        } catch(Exception e) {
+            fail();
+        }
+    }
+
+    @Test
+    public void reportInitErrorTestWrongStatusCode() {
+        int errorStatusCode = HTTP_INTERNAL_ERROR;
+        try {
+            RapidErrorType rapidErrorType = RapidErrorType.AfterRestoreError;
+
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(errorStatusCode);
+            mockWebServer.enqueue(mockResponse);
+
+            LambdaError lambdaError = new LambdaError(errorRequest, rapidErrorType);
+            lambdaRuntimeApiClientImpl.reportInitError(lambdaError);
+            fail();
+        } catch(LambdaRuntimeClientException e) {
+            String expectedUrl = "http://" + getHostnamePort() + "/2018-06-01/runtime/init/error";
+            String expectedMessage = expectedUrl + " Response code: '" + errorStatusCode + "'.";
+            assertEquals(expectedMessage, e.getLocalizedMessage());
+        } catch(Exception e) {
+            fail();
+        }
+    }
+
+    @Test
+    public void reportRestoreErrorTest() {
+        try {
+            RapidErrorType rapidErrorType = RapidErrorType.AfterRestoreError;
+
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(HTTP_ACCEPTED);
+            mockWebServer.enqueue(mockResponse);
+
+            LambdaError lambdaError = new LambdaError(errorRequest, rapidErrorType);
+            lambdaRuntimeApiClientImpl.reportRestoreError(lambdaError);
+            RecordedRequest recordedRequest = mockWebServer.takeRequest();
+            HttpUrl actualUrl = recordedRequest.getRequestUrl();
+            String expectedUrl = "http://" + getHostnamePort() + "/2018-06-01/runtime/restore/error";
+            assertEquals(expectedUrl, actualUrl.toString());
+
+            String userAgentHeader = recordedRequest.getHeader("User-Agent");
+            assertTrue(userAgentHeader.startsWith("aws-lambda-java/"));
+
+            String lambdaRuntimeErrorTypeHeader = recordedRequest.getHeader("Lambda-Runtime-Function-Error-Type");
+            assertEquals("Runtime.AfterRestoreError", lambdaRuntimeErrorTypeHeader);
+
+            String actualBody = recordedRequest.getBody().readUtf8();
+            assertEquals("{\"errorMessage\":\"testErrorMessage\",\"errorType\":\"testErrorType\",\"stackTrace\":[\"item0\",\"item1\",\"item2\"]}", actualBody);
+        } catch(Exception e) {
+            fail();
+        }
+    }
+
+    @Test
+    public void reportRestoreErrorTestWrongStatusCode() {
+        int errorStatusCode = HTTP_INTERNAL_ERROR;
+        try {
+            RapidErrorType rapidErrorType = RapidErrorType.AfterRestoreError;
+
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(errorStatusCode);
+            mockWebServer.enqueue(mockResponse);
+
+            LambdaError lambdaError = new LambdaError(errorRequest, rapidErrorType);
+            lambdaRuntimeApiClientImpl.reportRestoreError(lambdaError);
+            fail();
+        } catch(LambdaRuntimeClientException e) {
+            String expectedUrl = "http://" + getHostnamePort() + "/2018-06-01/runtime/restore/error";
+            String expectedMessage = expectedUrl + " Response code: '" + errorStatusCode + "'.";
+            assertEquals(expectedMessage, e.getLocalizedMessage());
+        } catch(Exception e) {
+            fail();
+        }
+    }
+
+    @Test
+    public void reportInvocationErrorTest() {
+        try {
+            RapidErrorType rapidErrorType = RapidErrorType.AfterRestoreError;
+
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(HTTP_ACCEPTED);
+            mockWebServer.enqueue(mockResponse);
+
+            LambdaError lambdaError = new LambdaError(errorRequest, rapidErrorType);
+            lambdaRuntimeApiClientImpl.reportInvocationError(requestId, lambdaError);
+            RecordedRequest recordedRequest = mockWebServer.takeRequest();
+            HttpUrl actualUrl = recordedRequest.getRequestUrl();
+            String expectedUrl = "http://" + getHostnamePort() + "/2018-06-01/runtime/invocation/1234/error";
+            assertEquals(expectedUrl, actualUrl.toString());
+
+            String userAgentHeader = recordedRequest.getHeader("User-Agent");
+            assertTrue(userAgentHeader.startsWith("aws-lambda-java/"));
+
+            String lambdaRuntimeErrorTypeHeader = recordedRequest.getHeader("Lambda-Runtime-Function-Error-Type");
+            assertEquals("Runtime.AfterRestoreError", lambdaRuntimeErrorTypeHeader);
+
+            String actualBody = recordedRequest.getBody().readUtf8();
+            assertEquals("{\"errorMessage\":\"testErrorMessage\",\"errorType\":\"testErrorType\",\"stackTrace\":[\"item0\",\"item1\",\"item2\"]}", actualBody);
+        } catch(Exception e) {
+            fail();
+        }
+    }
+
+    @Test
+    public void reportInvocationErrorTestWrongStatusCode() {
+        int errorStatusCode = HTTP_INTERNAL_ERROR;
+        try {
+            RapidErrorType rapidErrorType = RapidErrorType.AfterRestoreError;
+
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(errorStatusCode);
+            mockWebServer.enqueue(mockResponse);
+
+            LambdaError lambdaError = new LambdaError(errorRequest, rapidErrorType);
+            lambdaRuntimeApiClientImpl.reportInvocationError(requestId, lambdaError);
+            fail();
+        } catch(LambdaRuntimeClientException e) {
+            String expectedUrl = "http://" + getHostnamePort() + "/2018-06-01/runtime/invocation/1234/error";
+            String expectedMessage = expectedUrl + " Response code: '" + errorStatusCode + "'.";
+            assertEquals(expectedMessage, e.getLocalizedMessage());
+        } catch(Exception e) {
+            fail();
+        }
+    }
+
+    @Test
+    public void reportLambdaErrorWithXRayTest() {
+        try {
+            RapidErrorType rapidErrorType = RapidErrorType.AfterRestoreError;
+
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(HTTP_ACCEPTED);
+            mockWebServer.enqueue(mockResponse);
+
+            String workingDirectory = "my-test-directory";
+            List<String> paths = new ArrayList<String>();
+            paths.add("path-0");
+            paths.add("path-1");
+            paths.add("path-2");
+
+            List<StackElement> stackElements0 = new ArrayList<>();
+            stackElements0.add(new StackElement("label0", "path0", 0));
+            stackElements0.add(new StackElement("label1", "path1", 1));
+            stackElements0.add(new StackElement("label2", "path2", 2));
+            XRayException xRayException0 = new XRayException("my-test-message0", "my-test-type0", stackElements0);
+
+            List<StackElement> stackElements1 = new ArrayList<>();
+            stackElements1.add(new StackElement("label10", "path10", 0));
+            stackElements1.add(new StackElement("label11", "path11", 11));
+            stackElements1.add(new StackElement("label12", "path12", 12));
+            XRayException xRayException1 = new XRayException("my-test-message1", "my-test-type0", stackElements1);
+
+            List<XRayException> exceptions = new ArrayList<>();
+            exceptions.add(xRayException0);
+            exceptions.add(xRayException1);
+
+            XRayErrorCause xRayErrorCause = new XRayErrorCause(workingDirectory, exceptions, paths);
+            LambdaError lambdaError = new LambdaError(errorRequest, xRayErrorCause, rapidErrorType);
+            lambdaRuntimeApiClientImpl.reportInvocationError(requestId, lambdaError);
+            RecordedRequest recordedRequest = mockWebServer.takeRequest();
+
+            String xrayErrorCauseHeader = recordedRequest.getHeader("Lambda-Runtime-Function-XRay-Error-Cause");
+            assertEquals("{\"working_directory\":\"my-test-directory\",\"exceptions\":[{\"message\":\"my-test-message0\",\"type\":\"my-test-type0\",\"stack\":[{\"label\":\"label0\"," +
+                "\"path\":\"path0\",\"line\":0},{\"label\":\"label1\",\"path\":\"path1\",\"line\":1},{\"label\":\"label2\",\"path\":\"path2\",\"line\":2}]},{\"message\":\"my-test-message1\"," +
+                "\"type\":\"my-test-type0\",\"stack\":[{\"label\":\"label10\",\"path\":\"path10\",\"line\":0},{\"label\":\"label11\",\"path\":\"path11\",\"line\":11},{\"label\":\"label12\"," +
+                "\"path\":\"path12\",\"line\":12}]}],\"paths\":[\"path-0\",\"path-1\",\"path-2\"]}", xrayErrorCauseHeader);
+        } catch(Exception e) {
+            fail();
+        }
+    }
+
+    @Test
+    public void reportInvocationSuccessTest() {
+        try {
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(HTTP_ACCEPTED);
+            mockWebServer.enqueue(mockResponse);
+
+            String response = "{\"msg\":\"test\"}";
+            lambdaRuntimeApiClientImpl.reportInvocationSuccess(requestId, response.getBytes());
+            RecordedRequest recordedRequest = mockWebServer.takeRequest();
+            HttpUrl actualUrl = recordedRequest.getRequestUrl();
+            String expectedUrl = "http://" + getHostnamePort() + "/2018-06-01/runtime/invocation/1234/response";
+            assertEquals(expectedUrl, actualUrl.toString());
+
+            String actualBody = recordedRequest.getBody().readUtf8();
+            assertEquals("{\"msg\":\"test\"}", actualBody);
+        } catch(Exception e) {
+            e.printStackTrace();
+            fail();
+        }
+    }
+
+    @Test
+    public void restoreNextTest() {
+        try {
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(HTTP_OK);
+            mockWebServer.enqueue(mockResponse);
+
+            lambdaRuntimeApiClientImpl.restoreNext();
+            RecordedRequest recordedRequest = mockWebServer.takeRequest();
+            HttpUrl actualUrl = recordedRequest.getRequestUrl();
+            String expectedUrl = "http://" + getHostnamePort() + "/2018-06-01/runtime/restore/next";
+            assertEquals(expectedUrl, actualUrl.toString());
+
+            String actualBody = recordedRequest.getBody().readUtf8();
+            assertEquals("", actualBody);
+        } catch(Exception e) {
+            e.printStackTrace();
+            fail();
+        }
+    }
+
+    @Test
+    public void restoreNextWrongStatusCodeTest() {
+        int errorStatusCode = HTTP_INTERNAL_ERROR;
+        try {
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(errorStatusCode);
+            mockWebServer.enqueue(mockResponse);
+
+            lambdaRuntimeApiClientImpl.restoreNext();
+            fail();
+        } catch(LambdaRuntimeClientException e) {
+            String expectedUrl = "http://" + getHostnamePort() + "/2018-06-01/runtime/restore/next";
+            String expectedMessage = expectedUrl + " Response code: '" + errorStatusCode + "'.";
+            assertEquals(expectedMessage, e.getLocalizedMessage());
+        } catch(Exception e) {
+            fail();
+        }
+    }
+
+    @Test
+    public void nextTest() {
+        try {
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(HTTP_ACCEPTED);
+            mockResponse.setHeader("lambda-runtime-aws-request-id", "1234567890");
+            mockResponse.setHeader("Content-Type", "application/json");
+            mockWebServer.enqueue(mockResponse);
+
+            lambdaRuntimeApiClientImpl.nextInvocation();
+            RecordedRequest recordedRequest = mockWebServer.takeRequest();
+            HttpUrl actualUrl = recordedRequest.getRequestUrl();
+            String expectedUrl = "http://" + getHostnamePort() + "/2018-06-01/runtime/invocation/next";
+            assertEquals(expectedUrl, actualUrl.toString());
+
+            String actualBody = recordedRequest.getBody().readUtf8();
+            assertEquals("", actualBody);
+        } catch(Exception e) {
+            fail();
+        }
+    }
+
+
+    @Test
+    public void createUrlMalformedTest() {
+        RapidErrorType rapidErrorType = RapidErrorType.AfterRestoreError;
+        LambdaError lambdaError = new LambdaError(errorRequest, rapidErrorType);
+        RuntimeException thrown = assertThrows(RuntimeException.class, ()->{
+            lambdaRuntimeApiClientImpl.reportLambdaError("invalidurl", lambdaError, 100);
+        });
+        assertTrue(thrown.getLocalizedMessage().contains("java.net.MalformedURLException"));
+    }
+
+    @Test
+    public void lambdaReportErrorXRayHeaderTooLongTest() {
+        try {
+            RapidErrorType rapidErrorType = RapidErrorType.AfterRestoreError;
+
+            MockResponse mockResponse = new MockResponse();
+            mockResponse.setResponseCode(HTTP_ACCEPTED);
+            mockWebServer.enqueue(mockResponse);
+
+            String workingDirectory = "my-test-directory";
+            List<String> paths = new ArrayList<String>();
+            paths.add("path-0");
+
+            List<StackElement> stackElements = new ArrayList<>();
+            stackElements.add(new StackElement("label0", "path0", 0));
+            XRayException xRayException = new XRayException("my-test-message0", "my-test-type0", stackElements);
+
+            List<XRayException> exceptions = new ArrayList<>();
+            exceptions.add(xRayException);
+
+            XRayErrorCause xRayErrorCause = new XRayErrorCause(workingDirectory, exceptions, paths);
+            LambdaError lambdaError = new LambdaError(errorRequest, xRayErrorCause, rapidErrorType);
+            lambdaRuntimeApiClientImpl.reportLambdaError("http://" + getHostnamePort(), lambdaError, 10);
+            RecordedRequest recordedRequest = mockWebServer.takeRequest();
+
+            String xrayErrorCauseHeader = recordedRequest.getHeader("Lambda-Runtime-Function-XRay-Error-Cause");
+            assertNull(xrayErrorCauseHeader);
+        } catch(Exception e) {
+            fail();
+        }
+    }
+
+    private String getHostnamePort() {
+        return mockWebServer.getHostName() + ":" + mockWebServer.getPort();
+    }
+}
\ No newline at end of file