diff --git a/basics/checking-accounts/anchor/tests/litesvm.test.ts b/basics/checking-accounts/anchor/tests/litesvm.test.ts
index 1b7859c22..e39b9d68e 100644
--- a/basics/checking-accounts/anchor/tests/litesvm.test.ts
+++ b/basics/checking-accounts/anchor/tests/litesvm.test.ts
@@ -1,10 +1,22 @@
 import * as anchor from '@anchor-lang/core';
 import { Keypair, PublicKey, SystemProgram, Transaction } from '@solana/web3.js';
+import { assert } from 'chai';
 import { LiteSVMProvider } from 'anchor-litesvm';
 import { LiteSVM } from 'litesvm';
 import IDL from '../target/idl/checking_account_program.json' with { type: 'json' };
 import type { CheckingAccountProgram } from '../target/types/checking_account_program.ts';
 
+const expectAnchorError = async (promise: Promise<unknown>, code: string) => {
+    let caught: any;
+    try {
+        await promise;
+    } catch (error) {
+        caught = error;
+    }
+    assert.isDefined(caught, `expected the transaction to fail with ${code}`);
+    assert.strictEqual(caught?.error?.errorCode?.code, code, `expected ${code}, got: ${caught}`);
+};
+
 const PROGRAM_ID = new PublicKey(IDL.address);
 
 describe('LiteSVM example', () => {
@@ -48,4 +60,20 @@ describe('LiteSVM example', () => {
             })
             .rpc();
     });
+
+    it('Rejects an account our program does not own', async () => {
+        // accountToCreate was never created, so the runtime presents it as
+        // owned by the System Program — exactly what `owner = id()` must refuse.
+        await expectAnchorError(
+            program.methods
+                .checkAccounts()
+                .accounts({
+                    payer: wallet.publicKey,
+                    accountToCreate: accountToCreate.publicKey,
+                    accountToChange: accountToCreate.publicKey,
+                })
+                .rpc(),
+            'ConstraintOwner',
+        );
+    });
 });
diff --git a/basics/checking-accounts/anchor/tests/test.ts b/basics/checking-accounts/anchor/tests/test.ts
index a0ab321cf..f31da3d7a 100644
--- a/basics/checking-accounts/anchor/tests/test.ts
+++ b/basics/checking-accounts/anchor/tests/test.ts
@@ -1,7 +1,19 @@
 import * as anchor from '@anchor-lang/core';
 import { Keypair, SystemProgram, sendAndConfirmTransaction, Transaction } from '@solana/web3.js';
+import { assert } from 'chai';
 import type { CheckingAccountProgram } from '../target/types/checking_account_program.ts';
 
+const expectAnchorError = async (promise: Promise<unknown>, code: string) => {
+    let caught: any;
+    try {
+        await promise;
+    } catch (error) {
+        caught = error;
+    }
+    assert.isDefined(caught, `expected the transaction to fail with ${code}`);
+    assert.strictEqual(caught?.error?.errorCode?.code, code, `expected ${code}, got: ${caught}`);
+};
+
 describe('Anchor example', () => {
     const provider = anchor.AnchorProvider.env();
     anchor.setProvider(provider);
@@ -38,4 +50,20 @@ describe('Anchor example', () => {
             })
             .rpc();
     });
+
+    it('Rejects an account our program does not own', async () => {
+        // accountToCreate was never created, so the runtime presents it as
+        // owned by the System Program — exactly what `owner = id()` must refuse.
+        await expectAnchorError(
+            program.methods
+                .checkAccounts()
+                .accounts({
+                    payer: wallet.publicKey,
+                    accountToCreate: accountToCreate.publicKey,
+                    accountToChange: accountToCreate.publicKey,
+                })
+                .rpc(),
+            'ConstraintOwner',
+        );
+    });
 });