[Tests] add unit tests for node resolver module and jsnext:main resolution

Author: MustafaHaddara

resolvers/node/test/package-mains/jsnext/package.json

@@ -0,0 +1,4 @@
+{
+  "main": "lib/index.js",
+  "jsnext:main": "src/index.js"
+}

resolvers/node/test/package-mains/jsnext/src/index.js

@@ -0,0 +1,5 @@
+{
+  "main": "lib/index.js",
+  "module": "src/index.js",
+  "jsnext:main": "lib/index.js"
+}

resolvers/node/test/package-mains/module-and-jsnext/package.json

@@ -0,0 +1,4 @@
+{
+  "main": "lib/index.js",
+  "module": "src/index.js"
+}

resolvers/node/test/package-mains/module-and-jsnext/src/index.js

@@ -0,0 +1 @@
+{ "dummy": true }

resolvers/node/test/package-mains/module/package.json

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+'use strict';
+
+const chai = require('chai');
+const expect = chai.expect;
+const path = require('path');
+
+const webpack = require('../');
+
+const file = path.join(__dirname, 'package-mains', 'dummy.js');
+
+
+describe('packageMains', function () {
+  it('captures module', function () {
+    expect(webpack.resolve('./module', file)).property('path')
+      .to.equal(path.join(__dirname, 'package-mains', 'module', 'src', 'index.js'));
+  });
+
+  it('captures jsnext', function () {
+    expect(webpack.resolve('./jsnext', file)).property('path')
+      .to.equal(path.join(__dirname, 'package-mains', 'jsnext', 'src', 'index.js'));
+  });
+
+  it('captures module instead of jsnext', function () {
+    expect(webpack.resolve('./module-and-jsnext', file)).property('path')
+      .to.equal(path.join(__dirname, 'package-mains', 'module-and-jsnext', 'src', 'index.js'));
+  });
+});