feat(#3): implement initial public API tests

jest.config.js

@@ -0,0 +1,27 @@
+// jest.config.js
+module.exports = {
+  rootDir: './',
+  globals: {
+    __DEV__: true,
+    __PROD__: false
+  },
+  testEnvironment: 'node',
+  preset: "ts-jest",
+  verbose: true, // report individual test
+  bail: false, // enable to stop test when an error occur,
+  moduleDirectories: ['node_modules', 'src', 'test'],
+  testMatch: ['**/test/**/*.test.ts?(x)'],
+  testPathIgnorePatterns: ['node_modules/', 'dist/', '.json'],
+  collectCoverageFrom: [
+    'src/**/*.ts'
+  ],
+  coverageThreshold: {
+    // coverage strategy
+    global: {
+      branches: 80,
+      functions: 80,
+      lines: 50,
+      statements: -10
+    }
+  }
+};