feat: add LiteSVM tests for PDA Rent-Payer

* Implement tests for initializing the Rent Vault and creating new accounts using the Rent Vault.
* Validate lamports in the Rent Vault and new accounts after transactions.

Author: sol-warrior

basics/pda-rent-payer/anchor/tests/litesvm.test.ts

@@ -0,0 +1,93 @@
+import anchor from "@coral-xyz/anchor";
+import {
+	Keypair,
+	LAMPORTS_PER_SOL,
+	PublicKey,
+	SystemProgram,
+	Transaction,
+	TransactionInstruction,
+} from "@solana/web3.js";
+import { assert } from "chai";
+import { LiteSVM } from "litesvm";
+import IDL from "../target/idl/pda_rent_payer.json" with { type: "json" };
+
+describe("LiteSVM: PDA Rent-Payer", () => {
+	const svm = new LiteSVM();
+	const programId = new PublicKey(IDL.address);
+	const coder = new anchor.BorshCoder(IDL as anchor.Idl);
+	const payer = Keypair.generate();
+	svm.airdrop(payer.publicKey, BigInt(10000000000));
+
+	const programPath = new URL(
+		"../target/deploy/pda_rent_payer.so",
+		import.meta.url,
+	).pathname;
+	svm.addProgramFromFile(programId, programPath);
+
+	/**
+	 * generate PDA for the Rent Vault
+	 */
+	const [rentVaultPDA] = PublicKey.findProgramAddressSync(
+		[Buffer.from("rent_vault")],
+		programId,
+	);
+
+	it("Initialize the Rent Vault", () => {
+		const ixArgs = {
+			fund_lamports: new anchor.BN(LAMPORTS_PER_SOL),
+		};
+
+		const data = coder.instruction.encode("init_rent_vault", ixArgs);
+		const ix = new TransactionInstruction({
+			keys: [
+				{ pubkey: payer.publicKey, isSigner: true, isWritable: true },
+				{ pubkey: rentVaultPDA, isSigner: false, isWritable: true },
+				{ pubkey: SystemProgram.programId, isSigner: false, isWritable: false },
+			],
+			programId,
+			data,
+		});
+
+		const tx = new Transaction().add(ix);
+		tx.feePayer = payer.publicKey;
+		tx.recentBlockhash = svm.latestBlockhash();
+		tx.sign(payer);
+		svm.sendTransaction(tx);
+
+		/**
+		 * Fetch the account and check its rent vault account info
+		 */
+		const rentVaultAccountInfo = svm.getAccount(rentVaultPDA);
+
+		assert.equal(rentVaultAccountInfo.lamports, LAMPORTS_PER_SOL);
+	});
+
+	it("Create a new account using the Rent Vault", () => {
+		const newAccount = new Keypair();
+
+		const data = coder.instruction.encode("create_new_account", {});
+		const ix = new TransactionInstruction({
+			keys: [
+				{ pubkey: newAccount.publicKey, isSigner: true, isWritable: true },
+				{ pubkey: rentVaultPDA, isSigner: false, isWritable: true },
+				{ pubkey: SystemProgram.programId, isSigner: false, isWritable: false },
+			],
+			programId,
+			data,
+		});
+
+		const tx = new Transaction().add(ix);
+		tx.feePayer = payer.publicKey;
+		tx.recentBlockhash = svm.latestBlockhash();
+		tx.sign(payer, newAccount);
+		svm.sendTransaction(tx);
+
+		/**
+		 * Fetch the newAccount and check its rent
+		 */
+		const minLamports = svm.minimumBalanceForRentExemption(BigInt(0));
+		const newAccountInfo = svm.getAccount(newAccount.publicKey);
+
+		assert.equal(newAccountInfo.lamports, Number(minLamports));
+	});
+});