Initial testing with jest (#133)

* 🎉 initial testing with jest

* 👌 update test script names & remove package-lock.json

* 👌 add 'yarn test' step to circle-ci build workflow

jest.config.js

@@ -0,0 +1,31 @@
+process.env.VUE_CLI_BABEL_TARGET_NODE = true;
+process.env.VUE_CLI_BABEL_TRANSPILE_MODULES = true;
+
+module.exports = {
+  moduleDirectories: ['node_modules', 'app/javascript/src'],
+  moduleFileExtensions: ['js', 'jsx', 'json', 'vue', 'ts', 'tsx', 'vue'],
+  automock: false,
+  resetMocks: true,
+  transform: {
+    '^.+\\.vue$': 'vue-jest',
+    '.+\\.(css|styl|less|sass|scss|png|jpg|ttf|woff|woff2|svg)$':
+      'jest-transform-stub',
+    '^.+\\.jsx?$': 'babel-jest',
+  },
+  cacheDirectory: '<rootDir>/.jest-cache',
+  collectCoverage: false,
+  coverageDirectory: 'buildreports',
+  collectCoverageFrom: ['**/app/javascript/**/*.js'],
+  reporters: ['default'],
+  // setupTestFrameworkScriptFile: './tests/setup.ts',
+  transformIgnorePatterns: ['node_modules/*'],
+  moduleNameMapper: {
+    '^@/(.*)$': '<rootDir>/app/javascript/$1',
+  },
+  roots: ['<rootDir>/app/javascript'],
+  snapshotSerializers: ['jest-serializer-vue'],
+  testMatch: [
+    '**/app/javascript/**/*.spec.(js|jsx|ts|tsx)|**/__tests__/*.(js|jsx|ts|tsx)',
+  ],
+  testURL: 'http://localhost/',
+};