state: add more tests for block validation (#3674)

* Expose priv validators for use in testing

* Generalize block header validation test past height 1

* Remove ineffectual assignment

* Remove redundant SaveState call

* Reorder comment for clarity

* Use the block executor ApplyBlock function instead of implementing a stripped-down version of it

* Remove commented-out code

* Remove unnecessary test

The required tests already appear to be implemented (implicitly) through
the TestValidateBlockHeader test.

* Allow for catching of specific error types during TestValidateBlockCommit

* Make return error testable

* Clean up and add TestValidateBlockCommit code

* Fix formatting

* Extract function to create a new mock test app

* Update comment for clarity

* Fix comment

* Add skeleton code for evidence-related test

* Allow for addressing priv val by address

* Generalize test beyond a single validator

* Generalize TestValidateBlockEvidence past first height

* Reorder code to clearly separate tests and utility code

* Use a common constant for stop height for testing in state/validation_test.go

* Refactor errors to resemble existing conventions

* Fix formatting

* Extract common helper functions

Having the tests littered with helper functions makes them less easily
readable imho, so I've pulled them out into a separate file. This also
makes it easier to see what helper functions are available during
testing, so we minimize the chance of duplication when writing new
tests.

* Remove unused parameter

* Remove unused parameters

* Add field keys

* Remove unused height constant

* Fix typo

* Fix incorrect return error

* Add field keys

* Use separate package for tests

This refactors all of the state package's tests into a state_test
package, so as to keep any usage of the state package's internal methods
explicit.

Any internal methods/constants used by tests are now explicitly exported
in state/export_test.go

* Refactor: extract helper function to make, validate, execute and commit a block

* Rename state function to makeState

* Remove redundant constant for number of validators

* Refactor mock evidence registration into TestMain

* Remove extraneous nVals variable

* Replace function-level TODOs with file-level TODO and explanation

* Remove extraneous comment

* Fix linting issues brought up by GolangCI (pulled in from latest merge from develop)

state/export_test.go

@@ -0,0 +1,62 @@
+package state
+
+import (
+	abci "github.com/tendermint/tendermint/abci/types"
+	dbm "github.com/tendermint/tendermint/libs/db"
+	"github.com/tendermint/tendermint/types"
+)
+
+//
+// TODO: Remove dependence on all entities exported from this file.
+//
+// Every entity exported here is dependent on a private entity from the `state`
+// package. Currently, these functions are only made available to tests in the
+// `state_test` package, but we should not be relying on them for our testing.
+// Instead, we should be exclusively relying on exported entities for our
+// testing, and should be refactoring exported entities to make them more
+// easily testable from outside of the package.
+//
+
+const ValSetCheckpointInterval = valSetCheckpointInterval
+
+// UpdateState is an alias for updateState exported from execution.go,
+// exclusively and explicitly for testing.
+func UpdateState(
+	state State,
+	blockID types.BlockID,
+	header *types.Header,
+	abciResponses *ABCIResponses,
+	validatorUpdates []*types.Validator,
+) (State, error) {
+	return updateState(state, blockID, header, abciResponses, validatorUpdates)
+}
+
+// ValidateValidatorUpdates is an alias for validateValidatorUpdates exported
+// from execution.go, exclusively and explicitly for testing.
+func ValidateValidatorUpdates(abciUpdates []abci.ValidatorUpdate, params types.ValidatorParams) error {
+	return validateValidatorUpdates(abciUpdates, params)
+}
+
+// CalcValidatorsKey is an alias for the private calcValidatorsKey method in
+// store.go, exported exclusively and explicitly for testing.
+func CalcValidatorsKey(height int64) []byte {
+	return calcValidatorsKey(height)
+}
+
+// SaveABCIResponses is an alias for the private saveABCIResponses method in
+// store.go, exported exclusively and explicitly for testing.
+func SaveABCIResponses(db dbm.DB, height int64, abciResponses *ABCIResponses) {
+	saveABCIResponses(db, height, abciResponses)
+}
+
+// SaveConsensusParamsInfo is an alias for the private saveConsensusParamsInfo
+// method in store.go, exported exclusively and explicitly for testing.
+func SaveConsensusParamsInfo(db dbm.DB, nextHeight, changeHeight int64, params types.ConsensusParams) {
+	saveConsensusParamsInfo(db, nextHeight, changeHeight, params)
+}
+
+// SaveValidatorsInfo is an alias for the private saveValidatorsInfo method in
+// store.go, exported exclusively and explicitly for testing.
+func SaveValidatorsInfo(db dbm.DB, height, lastHeightChanged int64, valSet *types.ValidatorSet) {
+	saveValidatorsInfo(db, height, lastHeightChanged, valSet)
+}