electra: Improve test coverage for beacon-chain/core/electra/churn.go

[prestonvanloon]

What type of PR is this?

Other

What does this PR do? Why is it needed?

Using mutation testing to find various issues.

Which issues(s) does this PR fix?

┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╍┅
┃ 🧬 Mutant survived: beacon-chain/core/electra/churn.go → Arithmetic
┠┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄
┃ --- beacon-chain/core/electra/churn.go (original)
┃ +++ beacon-chain/core/electra/churn.go (mutated with 'Arithmetic')
┃ @@ -64,7 +64,7 @@
┃       if consolidationBalance > consolidationBalanceToConsume {
┃               balanceToProcess := consolidationBalance - consolidationBalanceToConsume
┃               // additional_epochs = (balance_to_process - 1) // per_epoch_consolidation_churn + 1
┃ -             additionalEpochs, err := math.Div64(uint64(balanceToProcess-1), uint64(perEpochConsolidationChurn))
┃ +             additionalEpochs, err := math.Div64(uint64(balanceToProcess+1), uint64(perEpochConsolidationChurn))
┃               if err != nil {
┃                       return 0, err
┃               }
┃
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╍┅

┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╍┅
┃ 🧬 Mutant survived: beacon-chain/core/electra/churn.go → Comparison
┠┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄
┃ --- beacon-chain/core/electra/churn.go (original)
┃ +++ beacon-chain/core/electra/churn.go (mutated with 'Comparison')
┃ @@ -61,7 +61,7 @@
┃       }
┃
┃       // Consolidation doesn't fit in the current earliest epoch.
┃ -     if consolidationBalance > consolidationBalanceToConsume {
┃ +     if consolidationBalance >= consolidationBalanceToConsume {
┃               balanceToProcess := consolidationBalance - consolidationBalanceToConsume
┃               // additional_epochs = (balance_to_process - 1) // per_epoch_consolidation_churn + 1
┃               additionalEpochs, err := math.Div64(uint64(balanceToProcess-1), uint64(perEpochConsolidationChurn))
┃
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╍┅

┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╍┅
┃ 🧬 Mutant survived: beacon-chain/core/electra/churn.go → Integer Decrement
┠┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄
┃ --- beacon-chain/core/electra/churn.go (original)
┃ +++ beacon-chain/core/electra/churn.go (mutated with 'Integer Decrement')
┃ @@ -64,7 +64,7 @@
┃       if consolidationBalance > consolidationBalanceToConsume {
┃               balanceToProcess := consolidationBalance - consolidationBalanceToConsume
┃               // additional_epochs = (balance_to_process - 1) // per_epoch_consolidation_churn + 1
┃ -             additionalEpochs, err := math.Div64(uint64(balanceToProcess-1), uint64(perEpochConsolidationChurn))
┃ +             additionalEpochs, err := math.Div64(uint64(balanceToProcess-0), uint64(perEpochConsolidationChurn))
┃               if err != nil {
┃                       return 0, err
┃               }
┃
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╍┅

┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╍┅
┃ 🧬 Mutant survived: beacon-chain/core/electra/churn.go → Integer Increment
┠┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄
┃ --- beacon-chain/core/electra/churn.go (original)
┃ +++ beacon-chain/core/electra/churn.go (mutated with 'Integer Increment')
┃ @@ -64,7 +64,7 @@
┃       if consolidationBalance > consolidationBalanceToConsume {
┃               balanceToProcess := consolidationBalance - consolidationBalanceToConsume
┃               // additional_epochs = (balance_to_process - 1) // per_epoch_consolidation_churn + 1
┃ -             additionalEpochs, err := math.Div64(uint64(balanceToProcess-1), uint64(perEpochConsolidationChurn))
┃ +             additionalEpochs, err := math.Div64(uint64(balanceToProcess-2), uint64(perEpochConsolidationChurn))
┃               if err != nil {
┃                       return 0, err
┃               }
┃
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╍┅

Other notes for review

This PR adds tests only to cover the above mutation scenarios.

Acknowledgements

• I have read CONTRIBUTING.md.
• I have included a uniquely named changelog fragment file.
• I have added a description to this PR with sufficient context for reviewers to understand this PR.