fix fake user creation based on username rules

Author: kentcdodds

tests/db-utils.ts

@@ -11,7 +11,7 @@ export function createUser() {
 	const username = unique({
 		firstName: firstName.toLowerCase(),
 		lastName: lastName.toLowerCase(),
-	})
+	}).replace(/[^a-z0-9_]/g, '_')
 	return {
 		username,
 		name: `${firstName} ${lastName}`,