diff --git a/src/main/java/me/goudham/APIWrapper.java b/src/main/java/me/goudham/APIWrapper.java
index a7fca8a..7af966a 100644
--- a/src/main/java/me/goudham/APIWrapper.java
+++ b/src/main/java/me/goudham/APIWrapper.java
@@ -36,7 +36,7 @@ import static me.goudham.APIUtils.paginationData;
 public class APIWrapper {
     private final String version = "1.0";
     private static final String host = "https://mywaifulist.moe/api/v1/";
-    private final String apiKey;
+    private String apiKey;
 
     private final APIMapper apiMapper;
     private final HttpClient httpClient;
@@ -67,7 +67,7 @@ public class APIWrapper {
      * cannot be decoded or the thread was interrupted while waiting to receive the data
      *
      */
-    private Result sendRequest(String param) throws APIResponseException {
+    Result sendRequest(String param) throws APIResponseException {
         CompletableFuture<Result> futureResult = CompletableFuture.supplyAsync(() -> {
             HttpRequest request = HttpRequest.newBuilder()
                     .uri(URI.create(host + param))
@@ -329,4 +329,12 @@ public class APIWrapper {
         Result userProfileResult = sendRequest("user/" + userId + "/lists/" + listId);
         return apiMapper.deserialize(userProfileResult, UserList.class);
     }
+
+    void setApiKey(String apiKey) {
+        this.apiKey = apiKey;
+    }
+
+    String getApiKey() {
+        return apiKey;
+    }
 }
diff --git a/src/test/java/me/goudham/APIWrapperTest.java b/src/test/java/me/goudham/APIWrapperTest.java
new file mode 100644
index 0000000..7f10a8c
--- /dev/null
+++ b/src/test/java/me/goudham/APIWrapperTest.java
@@ -0,0 +1,108 @@
+package me.goudham;
+
+import me.goudham.exception.APIResponseException;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import javax.net.ssl.SSLSession;
+import java.io.IOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpHeaders;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+import java.util.Optional;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+import static org.mockito.Mockito.*;
+
+class APIWrapperTest {
+
+    @Mock
+    private
+    HttpClient httpClient;
+
+    private APIWrapper sut;
+
+    @BeforeEach
+    void setUp() {
+        MockitoAnnotations.openMocks(this);
+        sut = new APIWrapper("ValidAPIKey", httpClient);
+    }
+
+    @Test
+    void successfullyReturn400WhenApiTokenInvalid() throws APIResponseException, IOException, InterruptedException {
+        sut.setApiKey("InvalidAPIKey");
+        HttpRequest expectedHttpRequest = buildHttpRequest(sut);
+        HttpResponse<String> expectedHttpResponse = build400HttpResponse();
+
+        doReturn(expectedHttpResponse).when(httpClient).send(expectedHttpRequest, HttpResponse.BodyHandlers.ofString());
+        doReturn(HttpClient.Version.HTTP_2).when(httpClient).version();
+
+        Result actualResult = sut.sendRequest("waifu/1");
+
+        assertThat(actualResult.getStatusCode(), is(400));
+        assertThat(actualResult.getBody(), is("{\"message\":\"Access denied - please check your token\",\"code\":400}"));
+        verify(httpClient, times(1)).send(expectedHttpRequest, HttpResponse.BodyHandlers.ofString());
+        verify(httpClient, times(1)).version();
+        verifyNoMoreInteractions(httpClient);
+    }
+
+    private HttpRequest buildHttpRequest(APIWrapper sut) {
+        return HttpRequest.newBuilder()
+                .uri(URI.create("https://mywaifulist.moe/api/v1/waifu/1"))
+                .version(HttpClient.Version.HTTP_2)
+                .timeout(Duration.ofSeconds(20))
+                .headers("Content-Type", "application/json", "apikey", sut.getApiKey())
+                .GET()
+                .build();
+    }
+
+    private HttpResponse<String> build400HttpResponse() {
+        return new HttpResponse<>() {
+            @Override
+            public int statusCode() {
+                return 400;
+            }
+
+            @Override
+            public HttpRequest request() {
+                return null;
+            }
+
+            @Override
+            public Optional<HttpResponse<String>> previousResponse() {
+                return Optional.empty();
+            }
+
+            @Override
+            public HttpHeaders headers() {
+                return null;
+            }
+
+            @Override
+            public String body() {
+                return "{\"message\":\"Access denied - please check your token\",\"code\":400}";
+            }
+
+            @Override
+            public Optional<SSLSession> sslSession() {
+                return Optional.empty();
+            }
+
+            @Override
+            public URI uri() {
+                return null;
+            }
+
+            @Override
+            public HttpClient.Version version() {
+                return null;
+            }
+        };
+    }
+}
\ No newline at end of file