add fs wrapper

internal/storage/fs.go

@@ -0,0 +1,21 @@
+package storage
+
+import (
+	"io/fs"
+	"os"
+)
+
+// FS is a wrapper that falls back to `os`.
+type FS struct {
+	FS fs.FS
+}
+
+// Open a file in the provided `fs.FS`. If none provided,
+// open via `os.Open`
+func (f FS) Open(name string) (fs.File, error) {
+	if f.FS == nil {
+		return os.Open(name)
+	}
+
+	return f.FS.Open(name)
+}

run.go

@@ -226,9 +226,7 @@ func runWithOptions(suiteName string, runner runner, opt Options) int {
 	}
 
 	runner.fmt = multiFmt.FormatterFunc(suiteName, output)
-	if opt.FS == nil {
-		opt.FS = os.DirFS("./")
-	}
+	opt.FS = storage.FS{FS: opt.FS}
 
 	if len(opt.FeatureContents) > 0 {
 		features, err := parser.ParseFromBytes(opt.Tags, opt.FeatureContents)
@@ -372,7 +370,7 @@ func getDefaultOptions() (*Options, error) {
 	}
 
 	opt.Paths = flagSet.Args()
-	opt.FS = os.DirFS("./")
+	opt.FS = storage.FS{FS: os.DirFS("./")}
 
 	return opt, nil
 }