js: add assign test (#66)

* feat: add validator scripts and assign instruction test

* chore: address maintainer feedback

Author: raushan728

clients/js/test/assign.test.ts

@@ -0,0 +1,52 @@
+import { appendTransactionMessageInstruction, fetchEncodedAccount, generateKeyPairSigner, pipe } from '@solana/kit';
+import { it, expect } from 'vitest';
+import { SYSTEM_PROGRAM_ADDRESS, getAssignInstruction, getTransferSolInstruction } from '../src';
+import {
+    createDefaultSolanaClient,
+    createDefaultTransaction,
+    generateKeyPairSignerWithSol,
+    signAndSendTransaction,
+} from './_setup';
+
+it('assigns a new owner to an account', async () => {
+    // 1. Setup client and payer.
+    const client = createDefaultSolanaClient();
+    const [payer, accountToAssign, newOwner] = await Promise.all([
+        generateKeyPairSignerWithSol(client),
+        generateKeyPairSigner(),
+        generateKeyPairSigner(),
+    ]);
+
+    // 2. Create the account first (so it exists on-chain).
+    // The account needs to exist to be assigned.
+    const space = 0n;
+    const lamports = await client.rpc.getMinimumBalanceForRentExemption(space).send();
+
+    const transfer = getTransferSolInstruction({
+        source: payer,
+        destination: accountToAssign.address,
+        amount: lamports,
+    });
+
+    // 3. Use getAssignInstruction to change the owner of accountToAssign to newOwner.
+    const assign = getAssignInstruction({
+        account: accountToAssign,
+        programAddress: newOwner.address,
+    });
+
+    // 4. Sign and send the transaction.
+    await pipe(
+        await createDefaultTransaction(client, payer),
+        tx => appendTransactionMessageInstruction(transfer, tx),
+        tx => appendTransactionMessageInstruction(assign, tx),
+        tx => signAndSendTransaction(client, tx),
+    );
+
+    // 5. Fetch the account data and verify the owner.
+    const fetchedAccount = await fetchEncodedAccount(client.rpc, accountToAssign.address);
+    // In solana/kit, 'programAddress' is the field for the account owner.
+    expect(fetchedAccount).toMatchObject({
+        exists: true,
+        programAddress: newOwner.address,
+    });
+});