create noErrorsOrAlternatives parser helper function

packages/parser/tests/test-util.ts

@@ -0,0 +1,19 @@
+import { ParseResult } from 'langium';
+
+const consoleMock = vi.spyOn(console, 'log').mockImplementation(() => {
+  return;
+});
+
+/**
+ * A helper test function that validate that the result doesn't have errors
+ * or any ambiguous alternatives from chevrotain.
+ *
+ * @param result - the result `parse` function.
+ */
+export function noErrorsOrAlternatives(result: ParseResult) {
+  expect(result.lexerErrors).toHaveLength(0);
+  expect(result.parserErrors).toHaveLength(0);
+
+  expect(consoleMock).not.toHaveBeenCalled();
+  consoleMock.mockReset();
+}