2 files changed, 109 insertions, 0 deletions
diff --git a/lib/test/data.go b/lib/test/data.go
index 281de010..d113e87c 100644
--- a/lib/test/data.go
+++ b/lib/test/data.go
@@ -207,6 +207,46 @@ func newData(name string) (data *Data) {
 	return data
 }
 
+// ExtractInput given the path to directory `destDir`, create all of the
+// [test.Data.Input] with key as its file name.
+//
+// If the input name contains "/", the path before the base name will be
+// created along with its parent as long as it is under the `destDir`.
+//
+// For example, given input name "a/b/c.txt", it will create path "a/b/"
+// inside `destDir` first, followed by file "c.txt" inside that path.
+func (data *Data) ExtractInput(destDir string) (err error) {
+	var (
+		logp    = `ExtractInput`
+		name    string
+		dir     string
+		base    string
+		path    string
+		content []byte
+	)
+	for name, content = range data.Input {
+		dir = filepath.Dir(name)
+		base = filepath.Base(name)
+		path = filepath.Join(destDir, dir)
+
+		if strings.HasPrefix(path, destDir) && dir != `.` && dir != `/` {
+			err = os.MkdirAll(path, 0700)
+			if err != nil {
+				return fmt.Errorf(`%s: %w`, logp, err)
+			}
+			path = filepath.Join(path, base)
+		} else {
+			path = filepath.Join(destDir, base)
+		}
+
+		err = os.WriteFile(path, content, 0600)
+		if err != nil {
+			return fmt.Errorf(`%s: %w`, logp, err)
+		}
+	}
+	return nil
+}
+
 func (data *Data) parse(content []byte) (err error) {
 	const (
 		stateFlag int = iota
diff --git a/lib/test/data_example_test.go b/lib/test/data_example_test.go
new file mode 100644
index 00000000..b544dacd
--- /dev/null
+++ b/lib/test/data_example_test.go
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: BSD-3-Clause
+// SPDX-FileCopyrightText: 2025 M. Shulhan <ms@kilabit.info>
+
+package test_test
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+
+	"git.sr.ht/~shulhan/pakakeh.go/lib/test"
+)
+
+func ExampleData_ExtractInput() {
+	var tempDir string
+	var err error
+	tempDir, err = os.MkdirTemp(``, ``)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	var data = &test.Data{
+		Input: map[string][]byte{
+			`dir/a.txt`:       []byte(`Content of dir/a.txt.`),
+			`dir/sub/b.txt`:   []byte(`Content of dir/sub/b.txt.`),
+			`c.txt`:           []byte(`Content of c.txt.`),
+			`dir/../../d.txt`: []byte(`Content of d.txt.`),
+		},
+	}
+
+	// The ExtractInput will create the following directory structures,
+	// including their files,
+	//
+	// ├── c.txt
+	// ├── dir
+	// │   ├── a.txt
+	// │   └── sub
+	// │       └── b.txt
+	// └── d.txt
+	//
+	err = data.ExtractInput(tempDir)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var listExtractedInput = []string{
+		filepath.Join(tempDir, `dir/a.txt`),
+		filepath.Join(tempDir, `dir/sub/b.txt`),
+		filepath.Join(tempDir, `c.txt`),
+		// Since the path of "dir/../../d.txt" is outside of the
+		// tempDir, the file will be created on root of tempDir.
+		filepath.Join(tempDir, `d.txt`),
+	}
+	var got []byte
+	for _, path := range listExtractedInput {
+		got, err = os.ReadFile(path)
+		if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf("%s\n", got)
+	}
+	// Output:
+	// Content of dir/a.txt.
+	// Content of dir/sub/b.txt.
+	// Content of c.txt.
+	// Content of d.txt.
+}