libs/fail: clean up `fail.go` (#3785)

* Clean up `fail.go`

- Clean up fail.go
- Remove unneeded Func `FailRand()`

closes #2729

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* add in commented lines

CHANGELOG_PENDING.md

@@ -23,6 +23,7 @@ program](https://hackerone.com/tendermint).
   - [libs] Remove unused `db/debugDB` and `common/colors.go` & `errors/errors.go` files (@marbar3778)
   - [libs] \#2432 Remove unused `common/heap.go` file (@marbar3778)
   - [libs] Remove unused `date.go`, `io.go`. Remove `GoPath()`, `Prompt()` and `IsDirEmpty()` functions from `os.go` (@marbar3778)
+  - [libs] Remove unused `FailRand()` func and minor clean up to `fail.go`(@marbar3778)
 
 - Blockchain Protocol
 

libs/fail/fail.go

@@ -2,36 +2,30 @@ package fail
 
 import (
 	"fmt"
-	"math/rand"
 	"os"
 	"strconv"
 )
 
-var callIndexToFail int
-
-func init() {
+func envSet() int {
 	callIndexToFailS := os.Getenv("FAIL_TEST_INDEX")
 
 	if callIndexToFailS == "" {
-		callIndexToFail = -1
+		return -1
 	} else {
 		var err error
-		callIndexToFail, err = strconv.Atoi(callIndexToFailS)
+		callIndexToFail, err := strconv.Atoi(callIndexToFailS)
 		if err != nil {
-			callIndexToFail = -1
+			return -1
 		}
+		return callIndexToFail
 	}
 }
 
 // Fail when FAIL_TEST_INDEX == callIndex
-var (
-	callIndex int //indexes Fail calls
-
-	callRandIndex       int  // indexes a run of FailRand calls
-	callRandIndexToFail = -1 // the callRandIndex to fail on in FailRand
-)
+var callIndex int //indexes Fail calls
 
 func Fail() {
+	callIndexToFail := envSet()
 	if callIndexToFail < 0 {
 		return
 	}
@@ -43,33 +37,6 @@ func Fail() {
 	callIndex += 1
 }
 
-// FailRand should be called n successive times.
-// It will fail on a random one of those calls
-// n must be greater than 0
-func FailRand(n int) {
-	if callIndexToFail < 0 {
-		return
-	}
-
-	if callRandIndexToFail < 0 {
-		// first call in the loop, pick a random index to fail at
-		callRandIndexToFail = rand.Intn(n)
-		callRandIndex = 0
-	}
-
-	if callIndex == callIndexToFail {
-		if callRandIndex == callRandIndexToFail {
-			Exit()
-		}
-	}
-
-	callRandIndex += 1
-
-	if callRandIndex == n {
-		callIndex += 1
-	}
-}
-
 func Exit() {
 	fmt.Printf("*** fail-test %d ***\n", callIndex)
 	os.Exit(1)