SPL Token 2022 initialize_group - "Invalid Instruction"

** The code is functional. The issue was with the test framework. See solution **.

I'm trying to create a group mint with token-2022.

I've followed the steps in:

https://github.com/solana-labs/solana-program-library/blob/master/token/program-2022-test/tests/token_group_initialize.rs

Being an interface, i've used the spl-token-2022 program id with all of the instructions. Have not provided my own implementations.

The instructions in order (full code at the end of the question):

1. create mint account (with enough lamports to cover group pointer)
2. initialise the group pointer extension on the mint created in (1)
3. initialise the mint
4. initialize_group

Instructions 1-3 execute correctly. However at step (4) I'm hit with "Invalid Instruction".

[2024-01-07T19:33:59.051326000Z DEBUG solana_runtime::message_processor::stable_log] Program TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb invoke [2][2024-01-07T19:33:59.051718000Z DEBUG solana_runtime::message_processor::stable_log] Program log: Error: Invalid instruction

Full code:

pub fn create_group_mint_combined(    payer: &Signer,    group_mint: &Signer,    authority: &AccountInfo,    authority_seeds: &[&[u8]],    max_group_size: u32,) -> Result {    let rent = Rent::get()?;    let mint_space =        ExtensionType::try_calculate_account_len::(&[ExtensionType::GroupPointer])?;    let mint_rent_lamports = rent.minimum_balance(mint_space);    invoke(&system_instruction::create_account(&payer.key(),&group_mint.key(),            mint_rent_lamports,            mint_space.try_into().unwrap(),&spl_token_2022::ID,        ),&[payer.to_account_info(), group_mint.to_account_info()],    )?;    let initialize_extension = spl_token_2022::extension::group_pointer::instruction::initialize(&spl_token_2022::ID,&group_mint.key(),        Some(authority.key()),        Some(group_mint.key()),    )    .unwrap();    invoke_signed(&initialize_extension,&[            group_mint.to_account_info(),            authority.to_account_info(),            group_mint.to_account_info(),        ],&[authority_seeds],    )?;    let initialize_ix = initialize_mint2(&spl_token_2022::ID,&group_mint.key(),&authority.key(),        Some(&authority.key()),        0,    )    .unwrap();    msg!("Invoke initialise mint2");    invoke_signed(&initialize_ix,&[group_mint.to_account_info()],&[authority_seeds],    )?;    msg!("Initialize group");    invoke_signed(&initialize_group(&spl_token_2022::ID,&group_mint.key(),&group_mint.key(),&authority.key(),            // Pubkey::new_unique().into(),            Some(authority.key()),            max_group_size,        ),&[            group_mint.to_account_info(),            authority.to_account_info(),        ],&[authority_seeds],    )?;    msg!("Invoked");    Ok(())}