diff --git a/.github/workflows/node.js.yml b/.github/workflows/node.js.yml
index d5e66fd..4ffc4d6 100644
--- a/.github/workflows/node.js.yml
+++ b/.github/workflows/node.js.yml
@@ -3,11 +3,7 @@
 
 name: Node.js CI
 
-on:
-  push:
-    branches: [ master ]
-  pull_request:
-    branches: [ master ]
+on: ["push", "pull_request"]
 
 jobs:
   build:
@@ -16,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [12.x, 14.x, 15.x]
+        node-version: [12.x]
         # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
 
     steps:
@@ -28,4 +24,8 @@ jobs:
     - name: Install dependencies
       run: yarn --frozen-lockfile
     - run: yarn build
-    - run: yarn test
+    - run: yarn test --coverage
+    - name: Coverage Report
+      uses: coverallsapp/github-action@master
+      with:
+        github-token: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.npmignore b/.npmignore
new file mode 100644
index 0000000..bd9e360
--- /dev/null
+++ b/.npmignore
@@ -0,0 +1,3 @@
+.github
+*.ts
+tsconfig*
diff --git a/README.md b/README.md
index b7a65df..e535312 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,5 @@
+[![Coverage Status](https://coveralls.io/repos/github/nohmad/graql/badge.svg?branch=master)](https://coveralls.io/github/nohmad/graql?branch=master)
+
 # Graql
 
 graql is a light-weight graphql client depends on nothing but 'node-fetch'.
diff --git a/index.ts b/index.ts
index ac846fd..33c08c0 100644
--- a/index.ts
+++ b/index.ts
@@ -2,7 +2,7 @@ import fetch from 'node-fetch';
 
 const APPLICATION_JSON = 'application/json';
 
-interface Options {
+interface FetchOptions {
   method?: string,
   headers?: {[key: string]: string},
   body?: string,
@@ -18,9 +18,9 @@ class Graql {
   endpoint: string;
   headers: {[key: string]: string};
   debug: boolean;
-  options: Options;
+  options: FetchOptions;
 
-  constructor(endpoint: string, options: Options = {debug: false}) {
+  constructor(endpoint: string, options: FetchOptions = {debug: false}) {
     this.endpoint = endpoint;
     this.debug = options.debug;
     delete options.debug;
@@ -32,7 +32,7 @@ class Graql {
     this.options = {method: 'POST', ...options};
   }
 
-  async fetch(request: GraphqlRequest, options: Options = {}) {
+  async fetch(request: GraphqlRequest, options: FetchOptions = {}) {
     const body = JSON.stringify(request);
     const headers = {...this.headers, ...options.headers};
     const _options = {...this.options, ...options, headers};
diff --git a/package.json b/package.json
index d86f3c2..5e36c03 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "graql",
-  "version": "0.3.0",
+  "version": "0.3.4",
   "author": "Gyoung-Yoon Noh <nohmad@gmail.com>",
   "repository": {
     "type": "git",
diff --git a/tsconfig-cjs.json b/tsconfig-cjs.json
index 3c1fb55..6c3026c 100644
--- a/tsconfig-cjs.json
+++ b/tsconfig-cjs.json
@@ -3,8 +3,5 @@
   "compilerOptions": {
     "module": "CommonJS",
     "outDir": "dist/cjs"
-  },
-  "exclude": [
-    "node_modules", "dist", "**/*.spec.ts"
-  ]
+  }
 }
diff --git a/tsconfig.json b/tsconfig.json
index 0b36d3e..836c599 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -4,6 +4,7 @@
     "module": "es2020",
     "moduleResolution": "node",
     "esModuleInterop": true,
+    "declaration": true,
     "outDir": "dist/esm"
   },
   "exclude": [