Chore: add tests for ruleset create utility

Build/lib/create-file.test.ts

@@ -0,0 +1,53 @@
+import { expect } from 'chai';
+import { fileEqual } from './create-file';
+
+// eslint-disable-next-line @typescript-eslint/require-await -- async iterable
+const createSource = async function *(input: string[]) {
+  for (const line of input) {
+    yield line;
+  }
+};
+
+const test = async (a: string[], b: string[], expected: boolean) => {
+  expect((await fileEqual(a, createSource(b)))).to.eq(expected);
+};
+
+describe('fileEqual', () => {
+  it('same', () => test(
+    ['A', 'B'],
+    ['A', 'B'],
+    true
+  ));
+
+  it('ignore comment', async () => {
+    await test(
+      ['# A', 'B'],
+      ['# B', 'B'],
+      true
+    );
+
+    await test(
+      ['# A', '# C', 'B'],
+      ['# A', '# D', 'B'],
+      true
+    );
+  });
+
+  it('comment more', () => test(
+    ['# A', 'B'],
+    ['# A', '# B', 'B'],
+    false
+  ));
+
+  it('larger', () => test(
+    ['A', 'B'],
+    ['A', 'B', 'C'],
+    false
+  ));
+
+  it('smaller', () => test(
+    ['A', 'B', 'C'],
+    ['A', 'B'],
+    false
+  ));
+});