Add missing unit tests for the PoS Module Validator Registration Command

[mosmartin]

Description

Based on the defined test cases, the following tests are missing from the implemented unit tests.

• verify()

  • params.validatorRegistrationFee != VALIDATOR_REGISTRATION_FEE
    • Expectation: Invalid transaction. Throw error at verify step.
  • name is longer than MAX_LENGTH_NAME characters long
    • Expectation: Invalid transaction. Throw error at verify step.
  • name is empty
    • Expectation: Invalid transaction. Throw error at verify step.
  • There exists already an entry in the name substore with store key trs.params.name
    • Expectation: Invalid transaction. Throw error at verify step.

• execute()

  • Transaction passes verification and registerValidatorKeys function from the Validators module does not throw

Motivation

These test will align with defined test cases and ensure complete coverage of the scenarios.

[mosmartin]

For the first test params.validatorRegistrationFee != VALIDATOR_REGISTRATION_FEE it's been covered by the should return error if transaction does not have enough balance for the registration fee test on L302.

For the second test name is longer than MAX_LENGTH_NAME characters long, the impl does not exist and I have created an issue here.

For the fourth test There exists already an entry in the name substore with store key trs.params.name, it's been covered by the should return error if store key name already exists in name store test on L256