paralellize external adder initialization

packages/adder-testing-library/utils.ts

@@ -254,7 +254,7 @@ export async function prepareSnaphotTests(
 	}
 }
 
-function runAdder(
+async function runAdder(
 	adder: AdderWithoutExplicitArgs,
 	cwd: string,
 	options: OptionValues<Record<string, Question>>
@@ -274,15 +274,25 @@ function runAdder(
 		changedFiles.forEach((file) => filesToFormat.add(file));
 	} else if (config.integrationType === 'external') {
 		try {
-			console.log('execute external adder');
-			execSync('npx ' + config.command, {
+			const program = spawn('npx', config.command.split(' '), {
+				stdio: 'pipe',
+				shell: true,
 				cwd,
-				env: Object.assign(process.env, config.environment ?? {}),
-				stdio: 'pipe'
+				env: Object.assign(process.env, config.environment ?? {})
+			});
+
+			await new Promise((resolve, reject) => {
+				program.on('exit', (code) => {
+					if (code == 0) {
+						resolve(undefined);
+					} else {
+						reject();
+					}
+				});
 			});
 		} catch (error) {
 			const typedError = error as Error;
-			throw new Error('Failed executing external command: ' + typedError.message);
+			throw new Error('Failed executing external command: ' + typedError);
 		}
 	} else {
 		throw new Error('Unknown integration type');