feat(utxo-lib): add assertEqualFixture utility function

This adds a helper to verify that a fixture matches an expected value.

Issue: BTC-2652

Co-authored-by: llm-git <[email protected]>

Author: OttoAllmendinger

modules/utxo-lib/test/fixture.util.ts

@@ -38,6 +38,10 @@ export async function readFixture<T>(path: string, defaultValue: T): Promise<T>
   }
 }
 
+export async function assertEqualFixture<T>(path: string, a: T): Promise<void> {
+  assert.deepStrictEqual(await readFixture(path, a), JSON.parse(toPrettyJSON(a)));
+}
+
 /**
  * @param a
  * @param b