What is -vbparams argument and what its the difference with -testactivationheight on Bitcoin functional tests?

-testactivationheight is defined here.

argsman.AddArg("-testactivationname@height.", "Set the activation height of 'name' (segwit, bip34, dersig, cltv, csv). (regtest-only)", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);

-vbparams is defined here.

argsman.AddArg("-vbparams=deployment:start:end[:min_activation_height]", "Use given start/end times and min_activation_height for specified version bits deployment (regtest-only)", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::CHAINPARAMS);

-testactivationheight is setting the name (segwit, bip34, dersig, cltv, csv) of the soft fork and the activation height (on regtest) for each soft fork. It is not testing the deployment of a particular soft fork (miner signaling etc, how a soft fork can get activated), just the block heights at which soft forks activate.

-vbparams is setting the start, end and min_activation_height of a deployment (on regtest). It is testing the deployment of a particular soft fork rather than just setting the activation height for various soft forks.

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