feat: create jest config

Author: G-Rath

jest.js

@@ -0,0 +1,35 @@
+module.exports = {
+  plugins: ['eslint-plugin-jest'],
+  extends: [
+    'plugin:eslint-plugin-jest/recommended',
+    'plugin:eslint-plugin-jest/style'
+  ],
+  rules: {
+    'jest/consistent-test-it': 'error',
+    'jest/expect-expect': [
+      'error',
+      // todo: TBD - this will need adjusting for react-testing-library
+      { assertFunctionNames: ['expect'] }
+    ],
+    'jest/lowercase-name': [
+      'error', // todo switch to top flag once merged
+      { ignore: ['describe'] }
+    ],
+    'jest/no-expect-resolves': 'warn',
+    'jest/no-if': 'error', // todo: rename to no-conditional-expect
+    'jest/no-large-snapshots': 'warn',
+    'jest/no-test-return-statement': 'error',
+    'jest/no-truthy-falsy': 'error',
+    'jest/prefer-called-with': 'error',
+    // you can disable this if you use a `beforeEach` setup script,
+    'jest/prefer-expect-assertions': 'warn',
+    'jest/prefer-hooks-on-top': 'error',
+    'jest/prefer-inline-snapshots': 'warn',
+    'jest/prefer-spy-on': 'error',
+    'jest/prefer-strict-equal': 'error',
+    'jest/prefer-todo': 'error',
+    'jest/require-to-throw-message': 'error',
+    'jest/require-top-level-describe': 'error',
+    'jest/valid-title': 'error'
+  }
+};

package-lock.json

@@ -10,7 +10,8 @@
   "license": "ISC",
   "author": "Gareth Jones",
   "files": [
-    "index.js"
+    "index.js",
+    "jest.js"
   ],
   "scripts": {
     "lint": "eslint . --ignore-pattern '!.eslintrc.js' --ext js,ts",
@@ -56,6 +57,7 @@
     "@typescript-eslint/parser": "^2.16.0",
     "eslint": "^6.8.0",
     "eslint-plugin-eslint-comments": "^3.1.2",
+    "eslint-plugin-jest": "^23.4.0",
     "eslint-plugin-local": "^1.0.0",
     "eslint-plugin-prettier": "^3.1.2",
     "husky": "^3.1.0",