Blueprints: add unit tests to the mkdir step (#1029)

Adds tests to the mkdir step.

Tests directory creation minding idempotence and recursivity. 

Part of the #756 effort.

---------

Co-authored-by: Adam Zielinski <adam@adamziel.com>

packages/playground/blueprints/src/lib/steps/mkdir.spec.ts

@@ -0,0 +1,42 @@
+import { NodePHP } from '@php-wasm/node';
+import { RecommendedPHPVersion } from '@wp-playground/wordpress';
+import { mkdir } from './mkdir';
+
+describe('Blueprint step mkdir', () => {
+	let php: NodePHP;
+	beforeEach(async () => {
+		php = await NodePHP.load(RecommendedPHPVersion);
+	});
+
+	it('should create a directory', async () => {
+		const directoryToCreate = '/php/dir';
+		await mkdir(php, {
+			path: directoryToCreate,
+		});
+		expect(php.isDir(directoryToCreate)).toBe(true);
+	});
+
+	it('should create a directory recursively', async () => {
+		const directoryToCreate = '/php/dir/subDir';
+		await mkdir(php, {
+			path: directoryToCreate,
+		});
+		expect(php.isDir(directoryToCreate)).toBe(true);
+	});
+
+	it('should do nothing when asked to create a directory that is allready there', async () => {
+		const existingDirectory = '/php/dir';
+		php.mkdir(existingDirectory);
+
+		const existingFile = '/php/dir/index.php';
+		php.writeFile(existingFile, `<?php echo 'Hello World';`);
+
+		mkdir(php, {
+			path: existingDirectory,
+		});
+
+		expect(php.readFileAsText(existingFile)).toBe(
+			`<?php echo 'Hello World';`
+		);
+	});
+});