Jest v23.* configuration with code coverage for SPFx projects

jest.config.json

{
  "collectCoverage": true,
  "coverageDirectory": "<rootDir>/../temp/test",
  "coverageReporters": [
    "json",
    "lcov",
    "text-summary"
  ],
  "coverageThreshold": {
    "global": {
      "branches": 50,
      "functions": 90,
      "lines": 100,
      "statements": 100
    }
  },
  "moduleFileExtensions": [
    "ts", 
    "tsx", 
    "js", 
    "json"
  ],
  "moduleNameMapper": {
    "\\.(css|scss)$": "identity-obj-proxy",
    "^resx-strings/en-us.json": "<rootDir>/node_modules/@microsoft/sp-core-library/lib/resx-strings/en-us.json"
  },
  "reporters":
  [
    "default",
    [ 
      "jest-junit", 
      { "output": "./temp/test/junit.xml" } 
    ]
  ],
  "rootDir": "../src",
  "testMatch": [
    "**/src/**/*.spec.+(ts|tsx|js)"
  ],
  "transform": {
    "^.+\\.(ts|tsx)$": "ts-jest"
  }
}