diff --git a/packages/cli/package.json b/packages/cli/package.json
index 049f3f903a..dc2ac1c5f7 100644
--- a/packages/cli/package.json
+++ b/packages/cli/package.json
@@ -114,6 +114,7 @@
     "@types/webpack": "^4.41.7",
     "@types/webpack-dev-server": "^3.10.0",
     "del": "^5.1.0",
+    "mock-fs": "^4.13.0",
     "nodemon": "^2.0.2",
     "ts-node": "^8.6.2"
   },
diff --git a/packages/cli/src/lib/builder/plugins.test.ts b/packages/cli/src/lib/builder/plugins.test.ts
new file mode 100644
index 0000000000..41504a700e
--- /dev/null
+++ b/packages/cli/src/lib/builder/plugins.test.ts
@@ -0,0 +1,178 @@
+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import fs from 'fs-extra';
+import mockFs from 'mock-fs';
+import {
+  NormalizedOutputOptions,
+  OutputAsset,
+  OutputChunk,
+  PluginContext,
+} from 'rollup';
+
+import { forwardFileImports } from './plugins';
+
+const context = {
+  meta: {
+    rollupVersion: '0.0.0',
+    watchMode: false,
+  },
+} as PluginContext;
+
+describe('forwardFileImports', () => {
+  it('should be created', () => {
+    const plugin = forwardFileImports({ include: /\.png$/ });
+    expect(plugin.name).toBe('forward-file-imports');
+  });
+
+  it('should call through to original external option', () => {
+    const plugin = forwardFileImports({ include: /\.png$/ });
+    const external = jest.fn((id: string) => id.endsWith('external'));
+
+    const options = plugin.options?.call(context, { external })!;
+    if (typeof options.external !== 'function') {
+      throw new Error('options.external is not a function');
+    }
+
+    expect(external).toHaveBeenCalledTimes(0);
+    expect(options.external('./my-module', '/dev/src/index.ts', false)).toBe(
+      false,
+    );
+    expect(external).toHaveBeenCalledTimes(1);
+    expect(options.external('./my-external', '/dev/src/index.ts', false)).toBe(
+      true,
+    );
+    expect(external).toHaveBeenCalledTimes(2);
+    expect(options.external('./my-image.png', '/dev/src/index.ts', false)).toBe(
+      true,
+    );
+    expect(external).toHaveBeenCalledTimes(3);
+    expect(options.external('./my-image.png', '/dev/src/index.ts', true)).toBe(
+      true,
+    );
+    expect(external).toHaveBeenCalledTimes(4);
+
+    expect(() =>
+      (options as any).external('./my-image.png', undefined, false),
+    ).toThrow('Unknown importer of file module ./my-image.png');
+  });
+
+  it('should handle original external array', () => {
+    const plugin = forwardFileImports({ include: /\.png$/ });
+
+    const options = plugin.options?.call(context, {
+      external: ['my-external'],
+    })!;
+    if (typeof options.external !== 'function') {
+      throw new Error('options.external is not a function');
+    }
+
+    expect(options.external('my-module', '/dev/src/index.ts', false)).toBe(
+      false,
+    );
+    expect(options.external('my-external', '/dev/src/index.ts', false)).toBe(
+      true,
+    );
+    expect(options.external('my-image.png', '/dev/src/index.ts', false)).toBe(
+      true,
+    );
+  });
+
+  describe('with mock fs', () => {
+    beforeEach(() => {
+      mockFs({
+        '/dev/src/my-module.ts': '',
+        '/dev/src/dir/my-image.png': 'my-image',
+      });
+    });
+
+    afterEach(() => {
+      mockFs.restore();
+    });
+
+    it('should extract files', async () => {
+      const plugin = forwardFileImports({ include: /\.png$/ });
+
+      const options = plugin.options?.call(context, {})!;
+      if (typeof options.external !== 'function') {
+        throw new Error('options.external is not a function');
+      }
+
+      expect(options.external('./my-module', '/dev/src/index.ts', false)).toBe(
+        false,
+      );
+      expect(
+        options.external('./my-image.png', '/dev/src/dir/index.ts', false),
+      ).toBe(true);
+
+      const outPath = '/dev/dist/dir/my-image.png';
+      await expect(fs.pathExists(outPath)).resolves.toBe(false);
+
+      await plugin.generateBundle?.call(
+        context,
+        { dir: '/dev/dist' } as NormalizedOutputOptions,
+        {
+          ['index.js']: {
+            type: 'chunk',
+            facadeModuleId: '/dev/src/index.ts',
+          } as OutputChunk,
+        },
+        false, // isWrite = false -> no write
+      );
+      await expect(fs.pathExists(outPath)).resolves.toBe(false);
+
+      await plugin.generateBundle?.call(
+        context,
+        { dir: '/dev/dist' } as NormalizedOutputOptions,
+        {
+          // output assets should not cause a write
+          ['index.js']: { type: 'asset' } as OutputAsset,
+          // missing facadeModuleId should not cause a write either
+          ['index2.js']: { type: 'chunk' } as OutputChunk,
+        },
+        true,
+      );
+      await expect(fs.pathExists(outPath)).resolves.toBe(false);
+
+      // output chunk + isWrite -> generate files
+      await plugin.generateBundle?.call(
+        context,
+        { dir: '/dev/dist' } as NormalizedOutputOptions,
+        {
+          ['index.js']: {
+            type: 'chunk',
+            facadeModuleId: '/dev/src/index.ts',
+          } as OutputChunk,
+        },
+        true,
+      );
+      await expect(fs.pathExists(outPath)).resolves.toBe(true);
+
+      // should not break when triggering another write
+      await plugin.generateBundle?.call(
+        context,
+        { file: '/dev/dist/my-output.js' } as NormalizedOutputOptions,
+        {
+          ['index.js']: {
+            type: 'chunk',
+            facadeModuleId: '/dev/src/index.ts',
+          } as OutputChunk,
+        },
+        true,
+      );
+    });
+  });
+});