ethereumjs-util check signed message

Question

I have the following signature verification function:

const verifySignature = (nonce: number, signature: string): string => {
    const msg = `Nonce: ${nonce}`
    const msgHex = bufferToHex(Buffer.from(msg));
    const msgBuffer = toBuffer(msgHex);
    const msgHash = hashPersonalMessage(msgBuffer);
    const signatureParams = fromRpcSig(signature);

    const publicKey = ecrecover(
        msgHash,
        signatureParams.v,
        signatureParams.r,
        signatureParams.s
    );
    const addressBuffer = publicToAddress(publicKey);
    return bufferToHex(addressBuffer);
}

I then have these tests:

describe('verify ethereum signature', () => {
    const echash = Buffer.from(
        '82ff40c0a986c6a5cfad4ddf4c3aa6996f1a7837f9c398e17e5de5cbd5a12b28',
        'hex'
      )
      const ecprivkey = Buffer.from(
        '3c9229289a6125f7fdf1885a77bb12c37a8d3b4962d936f7e3084dece32a3ca1',
        'hex'
      )

      const nonce = 1234567
      const expectedAddress = '0x58b4cafb614393925042e886f4b2413d799198f1'

    it('should return the users 0xaddress', () => {
        const signedMessage = ecsign(hashPersonalMessage(toBuffer(new Buffer(`Nonce: ${nonce}`, 'hex'))), ecprivkey)
        const signedString = toRpcSig(signedMessage.v, signedMessage.r, signedMessage.s)
        const address = verifySignature(nonce, signedString)
        assert.equal(address, expectedAddress)
    })

    it('should return the wrong address if the message is wrong', () => {
        const signedMessage = ecsign(hashPersonalMessage(toBuffer(new Buffer(`Wrong Message`, 'hex'))), ecprivkey)
        const signedString = toRpcSig(signedMessage.v, signedMessage.r, signedMessage.s)
        const address = verifySignature(nonce, signedString)
        assert.notEqual(address, expectedAddress)
    })
})

However, the signature always verifies, irrespectively of value. My question is, how can I ensure that the signed message is what is in fact expected?

Thanks!