fs: Add TestChdir()

internal/fs/helpers.go

@@ -1,6 +1,9 @@
 package fs
 
-import "os"
+import (
+	"os"
+	"testing"
+)
 
 // IsRegularFile returns true if fi belongs to a normal file. If fi is nil,
 // false is returned.
@@ -11,3 +14,25 @@ func IsRegularFile(fi os.FileInfo) bool {
 
 	return fi.Mode()&(os.ModeType|os.ModeCharDevice) == 0
 }
+
+// TestChdir changes the current directory to dest, the function back returns to the previous directory.
+func TestChdir(t testing.TB, dest string) (back func()) {
+	prev, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Logf("chdir to %v", dest)
+	err = os.Chdir(dest)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return func() {
+		t.Logf("chdir back to %v", prev)
+		err = os.Chdir(prev)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}