Add --version option

Change-Id: I4390f2df5a7e0c61c6f8a5233e5092f9f907435e
diff --git a/test/test.js b/test/test.js
index 3014c90..fbf38e1 100644
--- a/test/test.js
+++ b/test/test.js
@@ -1,5 +1,6 @@
 const { execSync } = require('child_process');
 const exp = require('constants');
+const packageVersion = require('../package.json').version;
 
 describe('conllu2cmc', () => {
   test('Test sparse mode', (done) => {
@@ -45,6 +46,13 @@
     done();
   });
 
+  test('Test version flag', (done) => {
+    const stdout = execSync('node src/index.js -V').toString().trim();
+
+    expect(stdout).toBe(packageVersion);
+    done();
+  });
+
   test('Regression test for hashtags: emit HST', (done) => {
     const testInput = [
       '# foundry = base',