Add test, fix callback.apply.

Author: vseventer

README.md

@@ -5,7 +5,48 @@
 `$ npm install custom-loader`
 
 ## Usage
+This module is useful for those times you want a loader but cant find or want to write one. How about just writing a function instead?
+
+### Example 1
+Performs a simple string replace.
+
+```
+{
+  module: {
+    rules: [{
+      test: /\.js$/,
+      use: {
+        loader: 'custom-loader',
+        options: {
+          callback: (source) => {
+            return source.replace('foo', 'bar');
+          }
+        }
+      }
+    }]
+  }
+};
+```
+
+### Example 2
+Using `[sharp](https://www.npmjs.com/package/sharp)`, returns the grayscale version of the resource.
+
 ```
+{
+  module: {
+    rules: [{
+      test: /\.(gif|jpe?g|png|svg|tiff|webp)(\?.*)?$/,
+      use: {
+        loader: 'custom-loader',
+        options: {
+          callback: (source, sourceMap, callback) => {
+            sharp().grayscale().toBuffer(callback);
+          }
+        }
+      }
+    }]
+  }
+};
 ```
 
 ## Changelog

index.js

@@ -43,7 +43,7 @@ module.exports = function (source, map) {
   }
 
   // Invoke custom loader.
-  return config.callback.apply(context, source, map, context.callback);
+  return config.callback.call(context, source, map, context.callback);
 };
 
 // Mark as raw.

main.js

@@ -19,6 +19,7 @@
     "mocha"        : "3.2.x",
     "semistandard" : "9.2.x",
     "snazzy"       : "6.0.x",
+    "tmp"          : "0.0.x",
     "webpack"      : "2.2.x"
   },
   "engines": {

package.json

@@ -1,4 +1,4 @@
-/* global describe, it */
+/* global describe, it, after */
 /*!
  * The MIT License (MIT)
  *
@@ -25,30 +25,78 @@
 // Strict mode.
 'use strict';
 
+// Standard lib.
+const fs = require('fs');
+const path = require('path');
+
 // Package modules.
+const expect = require('chai').expect;
+const tmp = require('tmp');
 const webpack = require('webpack');
 
+// Configure.
+const customLoader = require.resolve('../');
+
 // Test suite.
 describe('custom-loader', () => {
-  // Default webpack config.
-  const config = {
-    context: __dirname,
-    entry: './fixtures/entry',
-    // output: { filename: '[name].js' },
-    // module: {
-    //   rules: [
-    //     {
-    //       test: /.js$/,
-    //       use: 'custom-loader'
-    //     }
-    //   ]
-    // }
-  };
+  // Output.
+  const output = tmp.fileSync({ postfix: '.js' });
+  after(output.removeCallback);
 
   // Tests.
   it('should allow a custom loader', (done) => {
-    webpack(config, (err, stats) => {
-      console.log(err, stats);
+    const replacement = `module.exports = ${Math.random()};`;
+    webpack({
+      context: __dirname,
+      entry: './fixtures/entry.js',
+      output: {
+        filename: path.basename(output.name),
+        path: path.dirname(output.name)
+      },
+      module: {
+        rules: [
+          {
+            test: /.js$/,
+            use: {
+              loader: customLoader,
+              options: {
+                callback: (source) => replacement
+              }
+            }
+          }
+        ]
+      }
+    }, (err, stats) => {
+      if (stats.compilation.errors && stats.compilation.errors.length) {
+        err = stats.compilation.errors[0].error;
+      }
+
+      // Check file contents.
+      const contents = fs.readFileSync(output.name, { encoding: 'utf8' });
+      expect(contents).to.contain(replacement);
+
+      done(err);
+    });
+  });
+  it('should fail if a callback is not specified', (done) => {
+    webpack({
+      context: __dirname,
+      entry: './fixtures/entry.js',
+      output: {
+        filename: path.basename(output.name),
+        path: path.dirname(output.name)
+      },
+      module: {
+        rules: [
+          {
+            test: /.js$/,
+            use: customLoader
+          }
+        ]
+      }
+    }, (err, stats) => {
+      expect(stats).to.have.deep.property('compilation.errors[0].error.message');
+      expect(stats.compilation.errors[0].error.message).to.contain('callback');
       done(err);
     });
   });