fix(lint): add test file exemption and improve error handling

- Add black-box test file exemption to LatestImportsPredecessor cop
  (consistent with ConfigVersionImport and ConfigPackageName)
- Check strconv.Atoi error in versionFromImport for consistency
- Use 'must' instead of 'should' in error message for consistency

Assisted-By: docker-agent

Author: dgageot

lint/config_version_import.go

@@ -67,7 +67,7 @@ func importViolation(path string, dirVersion int, isLatest bool) string {
 		if _, ok := versionFromImport(path); ok {
 			return ""
 		}
-		return "pkg/config/latest should only import config version or types packages, not " + path
+		return "pkg/config/latest must only import config version or types packages, not " + path
 	}
 
 	// Versioned package (vN).

lint/configpath.go

@@ -55,7 +55,11 @@ func versionFromImport(importPath string) (int, bool) {
 	if m == nil {
 		return 0, false
 	}
-	n, _ := strconv.Atoi(m[1])
+	n, err := strconv.Atoi(m[1])
+	if err != nil {
+		// Should never happen since regex only captures digits.
+		return 0, false
+	}
 	return n, true
 }
 

lint/latest_imports_predecessor.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"go/ast"
 	"go/token"
+	"strings"
 
 	"github.com/dgageot/rubocop-go/cop"
 )
@@ -33,6 +34,11 @@ func (c *LatestImportsPredecessor) Check(fset *token.FileSet, file *ast.File) []
 	if configDir(filename) != "latest" {
 		return nil
 	}
+	// Black-box test files (package latest_test) are external to the package
+	// and may import what they please.
+	if strings.HasSuffix(file.Name.Name, "_test") {
+		return nil
+	}
 	highest, ok := highestSiblingVersion(filename)
 	if !ok {
 		return nil