Add test for examples given in the article

__tests__/index.test.js

@@ -0,0 +1,54 @@
+import { getPinnedReference, getPackageDependencies } from '../index';
+
+describe('Chapter 2', () => {
+  describe('getPinnedReference', () => {
+    it('should work with version range', async () => {
+      expect.assertions(1);
+      const pinnedReference = await getPinnedReference({
+        name: 'react',
+        reference: '~15.3.0',
+      });
+      expect(pinnedReference).toEqual({ name: 'react', reference: '15.3.2' });
+    });
+
+    it('should work with pinned version', async () => {
+      expect.assertions(1);
+      const pinnedReference = await getPinnedReference({
+        name: 'react',
+        reference: '15.3.0',
+      });
+      expect(pinnedReference).toEqual({ name: 'react', reference: '15.3.0' });
+    });
+
+    it('should work with path', async () => {
+      expect.assertions(1);
+      const pinnedReference = await getPinnedReference({
+        name: 'react',
+        reference: '/tmp/react-15.3.2.tar.gz',
+      });
+      expect(pinnedReference).toEqual({
+        name: 'react',
+        reference: '/tmp/react-15.3.2.tar.gz',
+      });
+    });
+  });
+});
+
+describe('Chapter 3', () => {
+  describe('getPackageDependencies', () => {
+    it('should resolve dependencies of a package', async () => {
+      expect.assertions(1);
+      const dependencies = await getPackageDependencies({
+        name: 'react',
+        reference: '15.6.1',
+      });
+      expect(dependencies).toEqual([
+        { name: 'create-react-class', reference: '^15.6.0' },
+        { name: 'fbjs', reference: '^0.8.9' },
+        { name: 'loose-envify', reference: '^1.1.0' },
+        { name: 'object-assign', reference: '^4.1.0' },
+        { name: 'prop-types', reference: '^15.5.10' },
+      ]);
+    });
+  });
+});

index.js

@@ -26,7 +26,7 @@ async function fetchPackage({name, reference}) {
 /////////////////////
 // --- Chapter 2 ---
 
-async function getPinnedReference({name, reference}) {
+export async function getPinnedReference({name, reference}) {
 
     // 1.0.0 is a valid range per semver syntax, but since it's also a pinned
     // reference, we don't actually need to process it. Less work, yeay!~
@@ -54,7 +54,7 @@ async function getPinnedReference({name, reference}) {
 
 import {readPackageJsonFromArchive} from './utilities';
 
-async function getPackageDependencies({name, reference}) {
+export async function getPackageDependencies({name, reference}) {
 
     let packageBuffer = await fetchPackage({name, reference});
     let packageJson = JSON.parse(await readPackageJsonFromArchive(packageBuffer));

package.json

@@ -1,7 +1,8 @@
 {
   "scripts": {
     "start": "babel-node index.js",
-    "install-self": "rm -rf temp && babel-node index . temp && rm -rf node_modules && mv temp/node_modules node_modules && rmdir temp"
+    "install-self": "rm -rf temp && babel-node index . temp && rm -rf node_modules && mv temp/node_modules node_modules && rmdir temp",
+    "test": "jest"
   },
   "dependencies": {
     "babel-cli": "^6.24.1",
@@ -14,5 +15,8 @@
     "semver": "^5.3.0",
     "tar-fs": "^1.15.3",
     "tar-stream": "^1.5.4"
+  },
+  "devDependencies": {
+    "jest": "^20.0.4"
   }
 }