Add test coverage

.gitignore

@@ -1,2 +1,6 @@
 node_modules
 package-lock.json
+
+.nyc_output
+coverage
+*.lcov

.travis.yml

@@ -3,3 +3,5 @@ node_js:
   - "node"
   - "8"
   - "6"
+script: npm run coverage
+after_success: npm run coveralls

README.md

@@ -8,6 +8,7 @@
 [![JavaScript Style Guide](https://img.shields.io/badge/code_style-standard-brightgreen.svg)](https://standardjs.com)
 [![license](https://img.shields.io/github/license/wikicite/wcite.svg)](https://github.com/wikicite/wcite/blob/master/LICENSE.md)
 [![Maintainability](https://api.codeclimate.com/v1/badges/b3bd79d9e25a521d0f57/maintainability)](https://codeclimate.com/github/wikicite/wcite/maintainability)
+[![Coverage Status](https://coveralls.io/repos/github/wikicite/wcite/badge.svg?branch=master)](https://coveralls.io/github/wikicite/wcite?branch=master)
 
 This JavaScript package provides [a command line client](#command-wcite) to
 fetch and manage bibliographic records from [Wikidata] and a [Pandoc filter] to

package.json

@@ -5,7 +5,14 @@
   "homepage": "https://github.com/wikicite/wcite#readme",
   "author": "Jakob Voß",
   "license": "MIT",
-  "keywords": ["wikidata", "wikicite", "citation", "bibtex", "pandoc", "csl"],
+  "keywords": [
+    "wikidata",
+    "wikicite",
+    "citation",
+    "bibtex",
+    "pandoc",
+    "csl"
+  ],
   "repository": {
     "type": "git",
     "url": "https://github.com/wikicite/wcite.git"
@@ -25,6 +32,8 @@
   ],
   "scripts": {
     "test": "mocha",
+    "coverage": "nyc mocha",
+    "coveralls": "nyc report --reporter=text-lcov | coveralls",
     "lint": "standard",
     "fix": "standard --fix",
     "lint-staged": "lint-staged",
@@ -48,8 +57,10 @@
     "yaml": "^1.3.1"
   },
   "devDependencies": {
+    "coveralls": "^3.0.2",
     "lint-staged": "^7.2.2",
     "mocha": "^5.2.0",
+    "nyc": "^13.3.0",
     "pre-commit": "^1.2.2",
     "should": "^13.2.3",
     "standard": "^12.0.1"