test(tests): test for bin.js

Closes #2

test/bin.js

@@ -1,9 +1,61 @@
 import test from 'ava'
+import path from 'path'
+import proxyquire from 'proxyquire'
 
-test.todo('test bin later')
-
-try {
-  require('../bin') // requiring now for coverage until this is tested
-} catch (error) {
-  // ignore the inevitable error
+let rules = []
+const processCwd = process.cwd
+const processExit = process.exit
+const consoleLog = console.log // eslint-disable-line no-console
+const specifiedFile = './fixtures/.eslintrc'
+const mainFile = path.join(process.cwd(), specifiedFile)
+const indexStub = {
+  './index': () => rules,
+}
+function outputStatement() {
+  return `New rules to add to the config: ${rules.join(', ')}.`
 }
+
+test.beforeEach((t) => {
+  process.argv.splice(2, process.argv.length)
+  process.exit = status => t.same(status, 1)
+  console.log = statement => t.same(statement, outputStatement()) // eslint-disable-line no-console
+})
+
+test.afterEach(() => {
+  process.cwd = processCwd
+  process.exit = processExit
+  console.log = consoleLog // eslint-disable-line no-console
+})
+
+test('no new rule and absolute path', () => {
+  process.argv[2] = mainFile
+  proxyquire('../bin', indexStub)
+})
+
+test('no new rule and relative path', () => {
+  process.argv[2] = specifiedFile
+  proxyquire('../bin', indexStub)
+})
+
+test('no new rule and no path', () => {
+  process.cwd = () => mainFile
+  proxyquire('../bin', indexStub)
+})
+
+test('new rule and absolute path', () => {
+  rules = ['foo']
+  process.argv[2] = mainFile
+  proxyquire('../bin', indexStub)
+})
+
+test('new rule and relative path', () => {
+  rules = ['foo', 'bar']
+  process.argv[2] = specifiedFile
+  proxyquire('../bin', indexStub)
+})
+
+test('new rule and no path', () => {
+  rules = ['foo', 'bar', 'baz']
+  process.cwd = () => mainFile
+  proxyquire('../bin', indexStub)
+})

test/fixtures/.eslintrc

@@ -0,0 +1,5 @@
+module.exports = {
+  rules: {
+    foo: true,
+  }
+}