Added logging test

.env.test

@@ -0,0 +1 @@
+TEST="This is the content of TEST variable"

README.md

@@ -41,6 +41,12 @@ Pass in the path to your `.env`-file using the `-p` flag:
 $ run.env -p my/path/env-file node my-node-app.js
 ```
 
+Run test locally:
+1. Change `.env.test` to `.env`
+2. Run `npm run test`. This command will create the build and simulate how `run.env` works on `test/test_app.js`
+3. If the test passed, it would log _"This is the content of TEST variable"_ which is the value of TEST variable in `.env` file
+4. Otherwise, it would log _"No value for process.env.TEST"_ 
+
 ## License
 
   [MIT](LICENSE)

package.json

@@ -38,7 +38,8 @@
     "build": "babel --presets es2015 src -d lib",
     "prepublish": "rm -fr lib/ && npm run build",
     "dev": "./node_modules/.bin/babel-node src/",
-    "start": "node lib/"
+    "start": "node lib/",
+    "test": "npm run build && node lib/index.js node test/test_app.js"
   },
   "engines": {
     "node": ">=6.1.0",

test/test_app.js

@@ -0,0 +1,17 @@
+try {
+  if (process.env.TEST) {
+    console.log(`\nValue of process.env.TEST: "${process.env.TEST}"`);
+  } else {
+    throw new Error('\nNo value for process.env.TEST');
+  }
+
+  if (process.env.NON_EXISTING_VAR) {
+    console.log(
+      `\nValue of process.env.TEST: "${process.env.NON_EXISTING_VAR}"`
+    );
+  } else {
+    throw new Error('\nNo value for process.env.NON_EXISTING_VAR');
+  }
+} catch (err) {
+  console.log(err.message);
+}