Add tests

.npmrc

@@ -0,0 +1 @@
+package-lock=false

package.json

@@ -5,10 +5,29 @@
   "files": [
     "index.js"
   ],
+  "scripts": {
+    "test": "jest",
+    "start": "npm test -- --watchAll",
+    "coverage": "npm test -- --coverage",
+    "prepublishOnly": "npm test",
+    "preversion": "npm test"
+  },
   "main": "index.js",
   "peerDependencies": {
     "webpack": "^5.0.0"
   },
+  "devDependencies": {
+    "file-loader": "^6.2.0",
+    "jest": "^27.0.4",
+    "memfs": "^3.2.2",
+    "url-loader": "^4.1.1",
+    "webpack": "^5.0.0"
+  },
+  "jest": {
+    "collectCoverageFrom": [
+      "index.js"
+    ]
+  },
   "license": "MIT",
   "repository": {
     "type": "git",

test/fixtures/nested.js

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+import file from './nested/component.js';
+
+__export__ = file;
+
+export default file;

test/fixtures/nested/component.js

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+import file from './files/file.png?foo=bar#hash';
+
+export default file;

test/fixtures/simple.js

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+import file from './file.svg?foo=bar#hash';
+
+__export__ = file;
+
+export default file;

test/index.test.js

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+const path = require('path');
+const { compile } = require('./utils');
+
+const loader = path.resolve(__dirname, '../index.js');
+const files = /\.(png|svg)$/;
+const entries = ['simple.js', 'nested.js'];
+const baseURIs = [
+  'http://localhost/',
+  'http://localhost/foo/',
+  'http://localhost/foo/bar',
+];
+const publicPaths = ['', '/', '/foo/', '/foo/bar', 'foo/', 'foo/bar'];
+const table = [];
+for (const entry of entries) {
+  for (const baseURI of baseURIs) {
+    for (const publicPath of publicPaths) {
+      table.push({ entry, baseURI, publicPath });
+    }
+  }
+}
+
+describe('loader', () => {
+  it.each(entries)('should match url-loader %s', async (entry) => {
+    const actual = await compile(
+      {
+        test: files,
+        oneOf: [
+          {
+            dependency: { not: ['url'] },
+            use: [loader],
+          },
+          {
+            type: 'asset',
+          },
+        ],
+      },
+      { entry }
+    );
+    expect(actual).toMatchSnapshot('result');
+
+    const expected = await compile(
+      {
+        test: files,
+        use: ['url-loader'],
+      },
+      { entry }
+    );
+    expect(actual).toEqual(expected);
+  });
+
+  it.each(table)(
+    'should match file-loader %s',
+    async ({ entry, publicPath, baseURI }) => {
+      const actual = await compile(
+        {
+          test: files,
+          oneOf: [
+            {
+              dependency: { not: ['url'] },
+              use: [loader],
+            },
+            {
+              type: 'asset/resource',
+            },
+          ],
+        },
+        { entry, publicPath, baseURI }
+      );
+      expect(actual).toMatchSnapshot('result');
+
+      const path = await compile(
+        {
+          test: files,
+          use: ['file-loader'],
+        },
+        { entry, publicPath }
+      );
+      // new-url-loader returns an URL where as file-loader returns a path
+      // both should resolve to the same URL when using the same baseURI
+      const expected = new URL(path, baseURI).toString();
+      expect(actual).toEqual(expected);
+    }
+  );
+});

test/utils.js

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+const Module = require('module');
+const path = require('path');
+const webpack = require('webpack');
+const { createFsFromVolume, Volume } = require('memfs');
+
+/**
+ * @see https://github.com/webpack-contrib/file-loader/blob/master/test/helpers/compile.js
+ * @see https://github.com/webpack-contrib/file-loader/blob/master/test/helpers/readAsset.js
+ * @see https://github.com/gregberge/svgr/blob/main/packages/webpack/src/index.test.js
+ */
+const compile = async (rule, { entry, publicPath = '', baseURI } = {}) => {
+  const compiler = webpack({
+    mode: 'production',
+    context: __dirname,
+    entry: `./fixtures/${entry}`,
+    output: {
+      publicPath,
+      hashDigestLength: 32, // default is 20 but file-loader uses 32
+    },
+    module: { rules: [rule] },
+  });
+  const fs = (compiler.outputFileSystem = createFsFromVolume(new Volume()));
+  const stats = await new Promise((resolve, reject) => {
+    compiler.run((err, stats) => (err ? reject(err) : resolve(stats)));
+  });
+  const dist = stats.compilation.outputOptions.path;
+  const content = fs.readFileSync(path.join(dist, 'main.js')).toString();
+  return execute(content, { baseURI }).toString();
+};
+
+/**
+ * @see https://github.com/webpack-contrib/file-loader/blob/master/test/helpers/execute.js
+ * @see https://github.com/webpack-contrib/url-loader/blob/master/test/helpers/execute.js
+ */
+const execute = (code, { baseURI } = {}) => {
+  const resource = 'test.js';
+  const mod = new Module(resource, module);
+  mod.paths = Module._nodeModulePaths(path.resolve(__dirname, './fixtures'));
+  mod.filename = resource;
+  mod._compile(script(code, { baseURI }), resource);
+  return mod.exports;
+};
+
+const script = (code, { baseURI = 'http://localhost/' } = {}) => `
+const document = { baseURI: ${JSON.stringify(baseURI)} };
+let __export__;
+${code};
+module.exports = __export__;
+`;
+
+module.exports = {
+  compile,
+};