chore: organize test files

packages/webpack5/scripts/jest.globals.d.ts

@@ -0,0 +1,12 @@
+// define test-specific globals here
+
+declare namespace jest {
+	interface Matchers<R, T> {
+		toHaveBeenWarned(): R;
+		toHaveBeenPrinted(): R;
+	}
+}
+
+declare global {
+	function mockFile(path: string, content: string);
+}

packages/webpack5/scripts/jest.mockFiles.ts

@@ -0,0 +1,42 @@
+import dedent from 'ts-dedent';
+
+const mockedFiles: { [path: string]: string } = {};
+
+export function mockFile(path, content) {
+	const unionFS = require('unionfs').default;
+	const Volume = require('memfs').Volume;
+
+	// reset to fs
+	unionFS.reset();
+
+	// add mocked file
+	mockedFiles[path] = dedent(content);
+
+	// create new volume
+	const vol = Volume.fromJSON(mockedFiles, '__jest__');
+
+	// use the new volume
+	unionFS.use(vol as any);
+}
+
+// a virtual mock for package.json
+jest.mock(
+	'__jest__/package.json',
+	() => ({
+		main: 'src/app.js',
+		devDependencies: {
+			typescript: '*',
+		},
+	}),
+	{ virtual: true }
+);
+
+jest.mock('fs', () => {
+	const fs = jest.requireActual('fs');
+	const unionFS = require('unionfs').default;
+	unionFS.reset = () => {
+		unionFS.fss = [fs];
+	};
+
+	return unionFS.use(fs);
+});

packages/webpack5/scripts/jest.mockWarn.ts

@@ -0,0 +1,64 @@
+import { printExpected, printReceived } from 'jest-matcher-utils';
+import dedent from 'ts-dedent';
+
+expect.extend({
+	toHaveBeenWarned(received: string) {
+		asserted.add(received);
+		const passed = warnSpy.mock.calls
+			.map((args) => args[1])
+			.some((arg) => arg.indexOf(received) > -1);
+		if (passed) {
+			return {
+				pass: true,
+				message() {
+					return `expected ${printReceived(received)} not to have been warned`;
+				},
+			};
+		}
+
+		const warnings = warnSpy.mock.calls.map((args) => args[1]).join('\n\n');
+		return {
+			pass: false,
+			message() {
+				return dedent`
+					expected ${printExpected(received)} to have been warned.
+
+					Actual warnings:
+
+					${warnings}
+				`;
+			},
+		};
+	},
+});
+
+let warnSpy: any;
+let asserted = new Set([]);
+beforeEach(() => {
+	asserted.clear();
+
+	warnSpy = jest.spyOn(console, 'warn');
+
+	warnSpy.mockImplementation(() => {});
+});
+
+afterEach(() => {
+	const assertedArray = Array.from(asserted);
+	const nonAssertedWarns = warnSpy.mock.calls
+		.map((args) => args[1])
+		.filter((received) => {
+			return !assertedArray.some((assertedMessage) => {
+				return received.indexOf(assertedMessage) > -1;
+			});
+		});
+
+	warnSpy.mockRestore();
+
+	if (nonAssertedWarns.length) {
+		throw new Error(dedent`
+			Test case printed unexpected warnings:
+
+			${printReceived(nonAssertedWarns.join('\n\n'))}
+		`);
+	}
+});

packages/webpack5/scripts/jest.setup.ts

@@ -0,0 +1,35 @@
+import './jest.mockFiles';
+// we are mocking the cwd for the tests, since webpack needs absolute paths
+// and we don't want them in tests
+process.cwd = () => '__jest__';
+
+jest.mock('cosmiconfig', () => ({
+	cosmiconfigSync(moduleName) {
+		return {
+			search() {
+				// no-op in tests
+				return null;
+			},
+		};
+	},
+}));
+
+jest.mock('path', () => {
+	const path = jest.requireActual('path');
+	return {
+		...path,
+		resolve(...args) {
+			if (args[0] === '__jest__') {
+				return path.join(...args);
+			}
+
+			const resolved = path.resolve(...args);
+			if (resolved.includes('__jest__')) {
+				const li = resolved.lastIndexOf('__jest__');
+				return resolved.substr(li);
+			}
+
+			return resolved;
+		},
+	};
+});