diff --git a/src/__tests__/lib/api/resources/Attachments.test.ts b/src/__tests__/lib/api/resources/Attachments.test.ts
new file mode 100644
index 0000000..508b8e9
--- /dev/null
+++ b/src/__tests__/lib/api/resources/Attachments.test.ts
@@ -0,0 +1,115 @@
+import axios from "axios";
+import AxiosMockAdapter from "axios-mock-adapter";
+
+import Attachments from "../../../../lib/api/resources/Attachments";
+import handleSendingError from "../../../../lib/axios-logger";
+import MailtrapError from "../../../../lib/MailtrapError";
+
+import CONFIG from "../../../../config";
+
+const { CLIENT_SETTINGS } = CONFIG;
+const { GENERAL_ENDPOINT } = CLIENT_SETTINGS;
+
+describe("lib/api/resources/Attachments: ", () => {
+  let mock: AxiosMockAdapter;
+  const accountId = 100;
+  const attachmentsAPI = new Attachments(axios, accountId);
+  const responseData = {
+    id: 1,
+    message_id: 101,
+    filename: "mock-filename",
+    attachment_type: "mock-attachment_type",
+    content_type: "mock-content_type",
+    content_id: "mock-content_id",
+    transfer_encoding: "mock-transfer_encoding",
+    attachment_size: 2048,
+    created_at: "mock-created_at",
+    updated_at: "mock-updated_at",
+    attachment_human_size: "mock-attachment_human_size",
+    download_path: "mock-download_path",
+  };
+  const inboxId = 1;
+  const messageId = 1;
+  const attachmentId = 100;
+
+  describe("class Attachments(): ", () => {
+    describe("init: ", () => {
+      it("initalizes with all necessary params.", () => {
+        expect(attachmentsAPI).toHaveProperty("get");
+        expect(attachmentsAPI).toHaveProperty("getList");
+      });
+    });
+  });
+
+  beforeAll(() => {
+    /**
+     * Init Axios interceptors for handling response.data, errors.
+     */
+    axios.interceptors.response.use(
+      (response) => response.data,
+      handleSendingError
+    );
+    mock = new AxiosMockAdapter(axios);
+  });
+
+  afterEach(() => {
+    mock.reset();
+  });
+
+  describe("getList(): ", () => {
+    it("successfully gets list of attachments.", async () => {
+      const endpoint = `${GENERAL_ENDPOINT}/api/accounts/${accountId}/inboxes/${inboxId}/messages/${messageId}/attachments`;
+      const expectedResponseData = [responseData];
+
+      mock.onGet(endpoint).reply(200, expectedResponseData);
+      const result = await attachmentsAPI.getList(inboxId, messageId);
+
+      expect(mock.history.get[0].url).toEqual(endpoint);
+      expect(result).toEqual(expectedResponseData);
+    });
+
+    it("fails with error.", async () => {
+      const expectedErrorMessage = "Request failed with status code 404";
+
+      expect.assertions(2);
+
+      try {
+        await attachmentsAPI.getList(inboxId, messageId);
+      } catch (error) {
+        expect(error).toBeInstanceOf(MailtrapError);
+
+        if (error instanceof MailtrapError) {
+          expect(error.message).toEqual(expectedErrorMessage);
+        }
+      }
+    });
+  });
+
+  describe("get(): ", () => {
+    it("successfully gets single attachment.", async () => {
+      const endpoint = `${GENERAL_ENDPOINT}/api/accounts/${accountId}/inboxes/${inboxId}/messages/${messageId}/attachments/${attachmentId}`;
+
+      mock.onGet(endpoint).reply(200, responseData);
+      const result = await attachmentsAPI.get(inboxId, messageId, attachmentId);
+
+      expect(mock.history.get[0].url).toEqual(endpoint);
+      expect(result).toEqual(responseData);
+    });
+
+    it("fails with error.", async () => {
+      const expectedErrorMessage = "Request failed with status code 404";
+
+      expect.assertions(2);
+
+      try {
+        await attachmentsAPI.get(inboxId, messageId, attachmentId);
+      } catch (error) {
+        expect(error).toBeInstanceOf(MailtrapError);
+
+        if (error instanceof MailtrapError) {
+          expect(error.message).toEqual(expectedErrorMessage);
+        }
+      }
+    });
+  });
+});