feat: major refactor, cleanup and jest tests

jest.config.js

@@ -0,0 +1,47 @@
+module.exports = {
+  testEnvironment: 'node',
+
+  expand: true,
+
+  forceExit: false,
+
+  // https://github.com/facebook/jest/pull/6747 fix warning here
+  // But its performance overhead is pretty bad (30+%).
+  // detectOpenHandles: true
+
+  setupFilesAfterEnv: ['./test/utils/setup'],
+
+  coverageDirectory: './coverage',
+
+  collectCoverageFrom: [
+    '**/src/**/*.js'
+  ],
+
+  coveragePathIgnorePatterns: [
+    'node_modules'
+  ],
+
+  testPathIgnorePatterns: [
+    'node_modules',
+    'old'
+  ],
+
+  transformIgnorePatterns: [
+    'node_modules'
+  ],
+
+  transform: {
+    '^.+\\.js$': 'babel-jest',
+    '.*\\.(vue)$': 'vue-jest'
+  },
+
+  moduleFileExtensions: [
+    'ts',
+    'js',
+    'json'
+  ],
+
+  reporters: [
+    'default'
+  ].concat(process.env.JEST_JUNIT_OUTPUT ? ['jest-junit'] : [])
+}