Add a test for discerning errors from warnings

When `emitErrors` is set to false, errors no longer abort the
compilation. However, the user might still want to know which
warnings are the result of stylelint errors, and which are the
results of stylelint warnings. These tests ensure that.

test/index.test.js

@@ -229,6 +229,44 @@ describe('stylelint-webpack-plugin', function () {
         });
     });
 
+    it('still indicates that errors are errors to the user, even when emitting them as warnings', function () {
+      var config = {
+        context: './test/fixtures/single-error',
+        entry: './index',
+        plugins: [
+          new StyleLintPlugin({
+            configFile: configFilePath,
+            quiet: true,
+            emitErrors: false
+          })
+        ]
+      };
+
+      return pack(assign({}, baseConfig, config))
+        .then(function (stats) {
+          expect(stats.compilation.warnings[0]).to.contain('✖');
+        });
+    });
+
+    it('still indicates that warnings are warnings to the user, even when emitting errors as warnings too', function () {
+      var config = {
+        context: './test/fixtures/rule-warning',
+        entry: './index',
+        plugins: [
+          new StyleLintPlugin({
+            configFile: configFilePath,
+            quiet: true,
+            emitErrors: false
+          })
+        ]
+      };
+
+      return pack(assign({}, baseConfig, config))
+        .then(function (stats) {
+          expect(stats.compilation.warnings[0]).to.contain('⚠');
+        });
+    });
+
     it('does not emit errors as warnings when asked not to', function () {
       var config = {
         context: './test/fixtures/single-error',