refactor: extract each matcher's tests to its own test file (#35)

* Add jest setup tests file

* Extract each matcher's tests to its own test file

Author: gnapse

jest.config.js

@@ -2,4 +2,5 @@ const jestConfig = require('kcd-scripts/jest')
 
 module.exports = Object.assign(jestConfig, {
   testEnvironment: 'jest-environment-jsdom',
+  setupTestFrameworkScriptFile: '<rootDir>/setupTests.js',
 })

setupTests.js

@@ -0,0 +1,4 @@
+import {plugins} from 'pretty-format'
+import './src/extend-expect'
+
+expect.addSnapshotSerializer(plugins.ConvertAnsi)