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)

types/errors.go

@@ -0,0 +1,41 @@
+package types
+
+import "fmt"
+
+type (
+	// ErrInvalidCommitHeight is returned when we encounter a commit with an
+	// unexpected height.
+	ErrInvalidCommitHeight struct {
+		Expected int64
+		Actual   int64
+	}
+
+	// ErrInvalidCommitPrecommits is returned when we encounter a commit where
+	// the number of precommits doesn't match the number of validators.
+	ErrInvalidCommitPrecommits struct {
+		Expected int
+		Actual   int
+	}
+)
+
+func NewErrInvalidCommitHeight(expected, actual int64) ErrInvalidCommitHeight {
+	return ErrInvalidCommitHeight{
+		Expected: expected,
+		Actual:   actual,
+	}
+}
+
+func (e ErrInvalidCommitHeight) Error() string {
+	return fmt.Sprintf("Invalid commit -- wrong height: %v vs %v", e.Expected, e.Actual)
+}
+
+func NewErrInvalidCommitPrecommits(expected, actual int) ErrInvalidCommitPrecommits {
+	return ErrInvalidCommitPrecommits{
+		Expected: expected,
+		Actual:   actual,
+	}
+}
+
+func (e ErrInvalidCommitPrecommits) Error() string {
+	return fmt.Sprintf("Invalid commit -- wrong set size: %v vs %v", e.Expected, e.Actual)
+}

types/validator_set.go

@@ -594,10 +594,10 @@ func (vals *ValidatorSet) VerifyCommit(chainID string, blockID BlockID, height i
 		return err
 	}
 	if vals.Size() != len(commit.Precommits) {
-		return fmt.Errorf("Invalid commit -- wrong set size: %v vs %v", vals.Size(), len(commit.Precommits))
+		return NewErrInvalidCommitPrecommits(vals.Size(), len(commit.Precommits))
 	}
 	if height != commit.Height() {
-		return fmt.Errorf("Invalid commit -- wrong height: %v vs %v", height, commit.Height())
+		return NewErrInvalidCommitHeight(height, commit.Height())
 	}
 	if !blockID.Equals(commit.BlockID) {
 		return fmt.Errorf("Invalid commit -- wrong block id: want %v got %v",