diff --git a/solidity/core/test/validator-manager/inboxMultisigValidatorManager.test.ts b/solidity/core/test/validator-manager/inboxMultisigValidatorManager.test.ts
index c4c5387d3..89bfdaacc 100644
--- a/solidity/core/test/validator-manager/inboxMultisigValidatorManager.test.ts
+++ b/solidity/core/test/validator-manager/inboxMultisigValidatorManager.test.ts
@@ -81,7 +81,7 @@ describe.only('InboxMultisigValidatorManager', () => {
       const signatures = await getCheckpointSignatures(
         root,
         index,
-        [validator0], // 1/2 signer is not a quorum
+        [validator0], // 1/2 signers is not a quorum
       );
 
       await expect(
diff --git a/solidity/core/test/validator-manager/multisigValidatorManager.test.ts b/solidity/core/test/validator-manager/multisigValidatorManager.test.ts
index 5181f32d4..ba7f00d1a 100644
--- a/solidity/core/test/validator-manager/multisigValidatorManager.test.ts
+++ b/solidity/core/test/validator-manager/multisigValidatorManager.test.ts
@@ -1,5 +1,5 @@
-import { ethers } from 'hardhat';
 import { expect } from 'chai';
+import { ethers } from 'hardhat';
 import { SignerWithAddress } from '@nomiclabs/hardhat-ethers/signers';
 import { Validator } from '@abacus-network/utils';
 
@@ -15,7 +15,7 @@ const OUTBOX_DOMAIN_HASH = ethers.utils.keccak256(
 );
 const QUORUM_THRESHOLD = 1;
 
-describe.only('MultisigValidatorManager', async () => {
+describe('MultisigValidatorManager', async () => {
   let validatorManager: TestMultisigValidatorManager,
     signer: SignerWithAddress,
     nonOwner: SignerWithAddress,
diff --git a/solidity/core/test/validator-manager/outboxMultisigValidatorManager.test.ts b/solidity/core/test/validator-manager/outboxMultisigValidatorManager.test.ts
new file mode 100644
index 000000000..75adc2d84
--- /dev/null
+++ b/solidity/core/test/validator-manager/outboxMultisigValidatorManager.test.ts
@@ -0,0 +1,121 @@
+import { expect } from 'chai';
+import { ethers } from 'hardhat';
+import { types, utils, Validator } from '@abacus-network/utils';
+import { SignerWithAddress } from '@nomiclabs/hardhat-ethers/signers';
+
+import {
+  Outbox,
+  Outbox__factory,
+  OutboxMultisigValidatorManager,
+  OutboxMultisigValidatorManager__factory,
+} from '../../types';
+import { getCheckpointSignatures } from './utils';
+
+const OUTBOX_DOMAIN = 1234;
+const INBOX_DOMAIN = 4321;
+const QUORUM_THRESHOLD = 2;
+
+describe('OutboxMultisigValidatorManager', () => {
+  let validatorManager: OutboxMultisigValidatorManager,
+    outbox: Outbox,
+    signer: SignerWithAddress,
+    validator0: Validator,
+    validator1: Validator;
+
+  before(async () => {
+    const signers = await ethers.getSigners();
+    [signer] = signers;
+    const [, validatorSigner0, validatorSigner1] = signers;
+    validator0 = await Validator.fromSigner(validatorSigner0, OUTBOX_DOMAIN);
+    validator1 = await Validator.fromSigner(validatorSigner1, OUTBOX_DOMAIN);
+  });
+
+  beforeEach(async () => {
+    const validatorManagerFactory = new OutboxMultisigValidatorManager__factory(
+      signer,
+    );
+    validatorManager = await validatorManagerFactory.deploy(
+      OUTBOX_DOMAIN,
+      [validator0.address, validator1.address],
+      QUORUM_THRESHOLD,
+    );
+
+    const outboxFactory = new Outbox__factory(signer);
+    outbox = await outboxFactory.deploy(OUTBOX_DOMAIN);
+    await outbox.initialize(validatorManager.address);
+  });
+
+  describe('#improperCheckpoint', () => {
+    const root = ethers.utils.formatBytes32String('test root');
+    const index = 1;
+
+    it('accepts an improper checkpoint if there is a quorum', async () => {
+      const signatures = await getCheckpointSignatures(
+        root,
+        index,
+        [validator0, validator1], // 2/2 signers, making a quorum
+      );
+
+      // Send message with signer address as msg.sender
+      await expect(
+        validatorManager.improperCheckpoint(
+          outbox.address,
+          root,
+          index,
+          signatures,
+        ),
+      )
+        .to.emit(validatorManager, 'ImproperCheckpoint')
+        .withArgs(
+          outbox.address,
+          root,
+          index,
+          signatures,
+        );
+      expect(await outbox.state()).to.equal(types.AbacusState.FAILED);
+    });
+
+    it('reverts if there is not a quorum', async () => {
+      const signatures = await getCheckpointSignatures(
+        root,
+        index,
+        [validator0], // 1/2 signers is not a quorum
+      );
+      
+      await expect(
+        validatorManager.improperCheckpoint(
+          outbox.address,
+          root,
+          index,
+          signatures
+        )
+      ).to.be.revertedWith('!quorum');
+    });
+
+    it('reverts if the checkpoint is not improper', async () => {
+      const message = `0x${Buffer.alloc(10).toString('hex')}`;
+      await outbox.dispatch(
+        INBOX_DOMAIN,
+        utils.addressToBytes32(signer.address),
+        message,
+      );
+      await outbox.checkpoint();
+      const [root, index] = await outbox.latestCheckpoint();
+
+      const signatures = await getCheckpointSignatures(
+        root,
+        index.toNumber(),
+        [validator0, validator1], // 2/2 signers, making a quorum
+      );
+      
+      await expect(
+        validatorManager.improperCheckpoint(
+          outbox.address,
+          root,
+          index,
+          signatures
+        )
+      ).to.be.revertedWith('!improper');
+    });
+  });
+});