diff --git a/__tests__/__snapshots__/index.test.ts.snap b/__tests__/__snapshots__/index.test.ts.snap
index ecef5afc..fff304b7 100644
--- a/__tests__/__snapshots__/index.test.ts.snap
+++ b/__tests__/__snapshots__/index.test.ts.snap
@@ -1,77 +1,5 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`already-processed: js 1`] = `
-"/* eslint-env browser */
-
-/** @type {HTMLElement[]} */
-const containers = [];
-/** @type {{prepend:HTMLStyleElement,append:HTMLStyleElement}[]} */
-const styleTags = [];
-
-/**
- * @param {string|undefined} css
- * @param {object} [options={}]
- * @param {boolean} [options.prepend]
- * @param {boolean} [options.singleTag]
- * @param {HTMLElement} [options.container]
- * @returns {void}
- */
-var injector_14187a73 = (css, options = {}) => {
-  if (!css || typeof document === \\"undefined\\") return;
-  const singleTag = typeof options.singleTag !== \\"undefined\\" ? options.singleTag : false;
-  const container = typeof options.container !== \\"undefined\\" ? options.container : document.head;
-  const position = options.prepend === true ? \\"prepend\\" : \\"append\\";
-
-  const createStyleTag = () => {
-    const styleTag = document.createElement(\\"style\\");
-    styleTag.type = \\"text/css\\";
-    if (position === \\"prepend\\" && container.firstChild) {
-      container.insertBefore(styleTag, container.firstChild);
-    } else {
-      container.append(styleTag);
-    }
-    return styleTag;
-  };
-
-  /** @type {HTMLStyleElement} */
-  let styleTag;
-
-  if (singleTag) {
-    let id = containers.indexOf(container);
-
-    if (id === -1) {
-      id = containers.push(container) - 1;
-      styleTags[id] = {};
-    }
-
-    if (styleTags[id] && styleTags[id][position]) {
-      styleTag = styleTags[id][position];
-    } else {
-      styleTag = styleTags[id][position] = createStyleTag();
-    }
-  } else {
-    styleTag = createStyleTag();
-  }
-
-  // strip potential UTF-8 BOM if css was read from a file
-  if (css.charCodeAt(0) === 0xfeff) css = css.slice(1);
-
-  if (styleTag.styleSheet) {
-    styleTag.styleSheet.cssText += css;
-  } else {
-    styleTag.textContent += css;
-  }
-};
-
-var css_2f84417a = \\".foo {\\\\n  color: red;\\\\n}\\\\n\\";
-const stylesheet = css_2f84417a;
-injector_14187a73(css_2f84417a);
-
-export default css_2f84417a;
-export { stylesheet };
-"
-`;
-
 exports[`basic postcss-config: js 1`] = `
 "'use strict';
 
@@ -1458,8 +1386,86 @@ console.log(style$1);
 "
 `;
 
-exports[`multiple-instances: js 1`] = `
-"/* eslint-env browser */
+exports[`multiple-instances already-processed: js 1`] = `
+"'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+/* eslint-env browser */
+
+/** @type {HTMLElement[]} */
+const containers = [];
+/** @type {{prepend:HTMLStyleElement,append:HTMLStyleElement}[]} */
+const styleTags = [];
+
+/**
+ * @param {string|undefined} css
+ * @param {object} [options={}]
+ * @param {boolean} [options.prepend]
+ * @param {boolean} [options.singleTag]
+ * @param {HTMLElement} [options.container]
+ * @returns {void}
+ */
+var injector_14187a73 = (css, options = {}) => {
+  if (!css || typeof document === \\"undefined\\") return;
+  const singleTag = typeof options.singleTag !== \\"undefined\\" ? options.singleTag : false;
+  const container = typeof options.container !== \\"undefined\\" ? options.container : document.head;
+  const position = options.prepend === true ? \\"prepend\\" : \\"append\\";
+
+  const createStyleTag = () => {
+    const styleTag = document.createElement(\\"style\\");
+    styleTag.type = \\"text/css\\";
+    if (position === \\"prepend\\" && container.firstChild) {
+      container.insertBefore(styleTag, container.firstChild);
+    } else {
+      container.append(styleTag);
+    }
+    return styleTag;
+  };
+
+  /** @type {HTMLStyleElement} */
+  let styleTag;
+
+  if (singleTag) {
+    let id = containers.indexOf(container);
+
+    if (id === -1) {
+      id = containers.push(container) - 1;
+      styleTags[id] = {};
+    }
+
+    if (styleTags[id] && styleTags[id][position]) {
+      styleTag = styleTags[id][position];
+    } else {
+      styleTag = styleTags[id][position] = createStyleTag();
+    }
+  } else {
+    styleTag = createStyleTag();
+  }
+
+  // strip potential UTF-8 BOM if css was read from a file
+  if (css.charCodeAt(0) === 0xfeff) css = css.slice(1);
+
+  if (styleTag.styleSheet) {
+    styleTag.styleSheet.cssText += css;
+  } else {
+    styleTag.textContent += css;
+  }
+};
+
+var css_2f84417a = \\".less {\\\\n  color: magenta;\\\\n}\\\\n\\";
+const stylesheet = css_2f84417a;
+injector_14187a73(css_2f84417a);
+
+exports.default = css_2f84417a;
+exports.stylesheet = stylesheet;
+"
+`;
+
+exports[`multiple-instances default: js 1`] = `
+"'use strict';
+
+/* eslint-env browser */
 
 /** @type {HTMLElement[]} */
 const containers = [];
@@ -1527,8 +1533,8 @@ injector_14187a73(css_2f84417a);
 var css_2f84417a$1 = \\".less {\\\\n  color: magenta;\\\\n}\\\\n\\";
 injector_14187a73(css_2f84417a$1);
 
-var css_2f84417a$2 = \\".mod_modular {\\\\n  color: royalblue;\\\\n}\\\\n\\";
-var mod = {\\"modular\\":\\"mod_modular\\",\\"modularalt\\":\\"mod_modular\\"};
+var css_2f84417a$2 = \\".mod_mod {\\\\n  color: royalblue;\\\\n}\\\\n\\";
+var mod = {\\"mod\\":\\"mod_mod\\"};
 injector_14187a73(css_2f84417a$2);
 
 console.log(mod);
diff --git a/__tests__/fixtures/multiple-instances/mod.mcss b/__tests__/fixtures/multiple-instances/mod.mcss
index 6c478eb0..4c762616 100644
--- a/__tests__/fixtures/multiple-instances/mod.mcss
+++ b/__tests__/fixtures/multiple-instances/mod.mcss
@@ -1,3 +1,3 @@
-.modular {
+.mod {
   color: royalblue;
 }
diff --git a/__tests__/helpers/index.ts b/__tests__/helpers/index.ts
index 47c93421..26718197 100644
--- a/__tests__/helpers/index.ts
+++ b/__tests__/helpers/index.ts
@@ -1,8 +1,7 @@
 /* eslint-disable jest/no-export */
 import path from "path";
 import fs from "fs-extra";
-import { rollup } from "rollup";
-import commonjs from "@rollup/plugin-commonjs";
+import { rollup, Plugin } from "rollup";
 
 import styles from "../../src";
 import { Options } from "../../src/types";
@@ -11,13 +10,10 @@ export interface WriteData {
   input: string;
   outDir?: string;
   options?: Options;
+  plugins?: Plugin[];
 }
 
-export interface Test extends WriteData {
-  title: string;
-}
-
-export interface TestData {
+export interface WriteResult {
   js: () => Promise<string>;
   css: () => Promise<string>;
   map: () => Promise<string>;
@@ -29,19 +25,9 @@ export interface TestData {
 export const fixture = (...args: string[]): string =>
   path.normalize(path.join(__dirname, "..", "fixtures", ...args));
 
-export async function write(data: WriteData): Promise<TestData> {
+export async function write(data: WriteData): Promise<WriteResult> {
   const outDir = fixture("dist", data.outDir || "");
 
-  const bundle = await rollup({
-    input: fixture(data.input),
-    plugins: [commonjs(), styles(data.options)],
-  });
-
-  await bundle.write({
-    format: "cjs",
-    file: path.join(outDir, "bundle.js"),
-  });
-
   const js = path.join(outDir, "bundle.js");
   const css =
     data.options && typeof data.options.extract === "string"
@@ -49,57 +35,62 @@ export async function write(data: WriteData): Promise<TestData> {
       : path.join(outDir, "bundle.css");
   const map = `${css}.map`;
 
-  const resData: TestData = {
+  const bundle = await rollup({
+    input: fixture(data.input),
+    plugins: data.plugins || [styles(data.options)],
+  });
+
+  await bundle.write({ format: "cjs", file: js });
+
+  const res: WriteResult = {
     js: () => fs.readFile(js, "utf8"),
     css: () => fs.readFile(css, "utf8"),
     map: () => fs.readFile(map, "utf8"),
     isCss: () => fs.pathExists(css),
     isMap: () => fs.pathExists(map),
-    isFile: (file: string) => fs.pathExists(path.join(outDir, file)),
+    isFile: file => fs.pathExists(path.join(outDir, file)),
   };
 
-  return resData;
+  return res;
+}
+
+export interface TestData extends WriteData {
+  title: string;
 }
 
-export function validate({ title, input, outDir, options = {} }: Test): void {
-  test(
-    title,
-    async () => {
-      let res;
-      try {
-        res = await write({ input, outDir, options });
-      } catch (error) {
-        const frame = error.codeFrame || error.snippet;
-        if (frame) throw new Error(`${frame} ${error.message}`);
-        throw error;
-      }
-
-      await expect(res.js()).resolves.toMatchSnapshot("js");
-
-      if (options.extract) {
-        await expect(res.isCss()).resolves.toBeTruthy();
-        await expect(res.css()).resolves.toMatchSnapshot("css");
-      }
-
-      const sourceMap = options && options.sourceMap;
-      if (sourceMap === "inline") {
-        await expect(res.isMap()).resolves.toBeFalsy();
-      } else if (sourceMap === true) {
-        await expect(res.isMap()).resolves.toBe(Boolean(options.extract));
-        if (options.extract) await expect(res.map()).resolves.toMatchSnapshot("map");
-      }
-    },
-    30000,
-  );
+export function validate(data: TestData): void {
+  const options = data.options || {};
+  test(data.title, async () => {
+    let res;
+    try {
+      res = await write(data);
+    } catch (error) {
+      const frame = error.codeFrame || error.snippet;
+      if (frame) throw new Error(`${frame} ${error.message}`);
+      throw error;
+    }
+
+    await expect(res.js()).resolves.toMatchSnapshot("js");
+
+    if (options.extract) {
+      await expect(res.isCss()).resolves.toBeTruthy();
+      await expect(res.css()).resolves.toMatchSnapshot("css");
+    }
+
+    const sourceMap = options && options.sourceMap;
+    if (sourceMap === "inline") {
+      await expect(res.isMap()).resolves.toBeFalsy();
+    } else if (sourceMap === true) {
+      await expect(res.isMap()).resolves.toBe(Boolean(options.extract));
+      if (options.extract) await expect(res.map()).resolves.toMatchSnapshot("map");
+    }
+  });
 }
 
-export function validateMany(groupName: string, tests: Test[]): void {
+export function validateMany(groupName: string, testDatas: TestData[]): void {
   describe(groupName, () => {
-    for (const test of tests) {
-      validate({
-        ...test,
-        outDir: path.join(groupName, test.title),
-      });
+    for (const testData of testDatas) {
+      validate({ ...testData, outDir: path.join(groupName, testData.title) });
     }
   });
 }
diff --git a/__tests__/index.test.ts b/__tests__/index.test.ts
index 523577f5..7b80e22b 100644
--- a/__tests__/index.test.ts
+++ b/__tests__/index.test.ts
@@ -1,5 +1,3 @@
-import path from "path";
-import fs from "fs-extra";
 import { rollup } from "rollup";
 
 import styles from "../src";
@@ -7,8 +5,6 @@ import styles from "../src";
 import { fixture, validateMany, write } from "./helpers";
 import { humanlizePath } from "../src/utils/path-utils";
 
-beforeAll(() => fs.remove(fixture("dist")));
-
 validateMany("basic", [
   {
     title: "simple",
@@ -258,6 +254,23 @@ validateMany("less", [
   },
 ]);
 
+validateMany("multiple-instances", [
+  {
+    title: "default",
+    input: "multiple-instances/index.js",
+    plugins: [
+      styles({ extensions: [".css"], use: [] }),
+      styles({ extensions: [], use: ["less"] }),
+      styles({ extensions: [".mcss"], use: [], modules: true, namedExports: true }),
+    ],
+  },
+  {
+    title: "already-processed",
+    input: "multiple-instances/bar.less",
+    plugins: [styles(), styles()],
+  },
+]);
+
 test("on-extract-fn", async () => {
   const res = await write({
     input: "simple/index.js",
@@ -311,40 +324,3 @@ test("augment-chunk-hash", async () => {
   expect(barHash).not.toEqual(fooOneHash);
   expect(barHash).not.toEqual(fooTwoHash);
 });
-
-test("already-processed", async () => {
-  const bundle = await rollup({
-    input: fixture("simple/foo.css"),
-    plugins: [styles(), styles()],
-  });
-
-  const outDir = fixture("dist", "already-processed");
-  const { output } = await bundle.write({ dir: outDir });
-  const outfile = path.join(outDir, output[0].fileName);
-
-  await expect(fs.pathExists(outfile)).resolves.toBeTruthy();
-  await expect(fs.readFile(outfile, "utf8")).resolves.toMatchSnapshot("js");
-});
-
-test("multiple-instances", async () => {
-  const bundle = await rollup({
-    input: fixture("multiple-instances/index.js"),
-    plugins: [
-      styles({ extensions: [".css"], use: [] }),
-      styles({ extensions: [], use: ["less"] }),
-      styles({
-        extensions: [".mcss"],
-        use: [],
-        modules: true,
-        namedExports: name => `${name}alt`,
-      }),
-    ],
-  });
-
-  const outDir = fixture("dist", "multiple-instances");
-  const { output } = await bundle.write({ dir: outDir });
-  const outfile = path.join(outDir, output[0].fileName);
-
-  await expect(fs.pathExists(outfile)).resolves.toBeTruthy();
-  await expect(fs.readFile(outfile, "utf8")).resolves.toMatchSnapshot("js");
-});
diff --git a/__tests__/setup.ts b/__tests__/setup.ts
index c8accf05..1accd37e 100644
--- a/__tests__/setup.ts
+++ b/__tests__/setup.ts
@@ -1,3 +1,8 @@
 // eslint-disable-next-line node/no-extraneous-import
 import "expect-puppeteer";
+
+import fs from "fs-extra";
+import { fixture } from "./helpers";
+
 jest.setTimeout(30000);
+beforeAll(() => fs.remove(fixture("dist")));
diff --git a/src/loaders/postcss/index.ts b/src/loaders/postcss/index.ts
index 8ac3b679..54dd2a2e 100644
--- a/src/loaders/postcss/index.ts
+++ b/src/loaders/postcss/index.ts
@@ -142,7 +142,7 @@ const loader: Loader<PostCSSLoaderOptions> = {
         .relative()
         .toCommentData();
 
-    let output = "";
+    let output = "\n";
     if (options.namedExports) {
       const json = modulesExports[this.id];
 
@@ -158,21 +158,21 @@ const loader: Loader<PostCSSLoaderOptions> = {
 
         if (!json[newName]) json[newName] = json[name];
 
-        output += `\nexport const ${newName} = ${JSON.stringify(json[name])};`;
+        output += `export const ${newName} = ${JSON.stringify(json[name])};\n`;
       }
     }
 
     const cssVarName = safeId("css");
     if (options.extract) {
-      output += `\nexport default ${JSON.stringify(modulesExports[this.id])};`;
+      output += `export default ${JSON.stringify(modulesExports[this.id])};\n`;
       extracted = { id: this.id, code: res.css, map };
     } else {
       const defaultExport = supportModules ? JSON.stringify(modulesExports[this.id]) : cssVarName;
-      output += `\n${[
+      output += `${[
         `var ${cssVarName} = ${JSON.stringify(res.css)};`,
         `export const stylesheet = ${cssVarName};`,
         `export default ${defaultExport};`,
-      ].join("\n")}`;
+      ].join("\n")}\n`;
     }
 
     if (!options.extract && options.inject) {
@@ -190,10 +190,10 @@ const loader: Loader<PostCSSLoaderOptions> = {
         );
         const injectorData =
           typeof options.inject === "object" ? `,${JSON.stringify(options.inject)}` : "";
-        output += `\n${[
+        output += `${[
           `import ${injectorName} from '${injectorPath}';`,
           `${injectorName}(${cssVarName}${injectorData});`,
-        ].join("\n")}`;
+        ].join("\n")}\n`;
       }
     }