How to Use Test Fixtures and testdata in Go

Store test data files in a testdata directory relative to your test file, then load them using os.ReadFile with filepath.Join and filepath.Dir to ensure portability.

package mypkg

import (
	"os"
	"path/filepath"
	"testing"
)

func TestExample(t *testing.T) {
	// Locate testdata relative to this test file
	dir := filepath.Dir("testdata")
	data, err := os.ReadFile(filepath.Join(dir, "testdata", "input.txt"))
	if err != nil {
		t.Fatalf("failed to read testdata: %v", err)
	}
	// Use data...
}

Note: The go test command automatically includes files in a testdata directory when running tests, so you do not need to add them to your build manually.

Test fixtures are data files your tests need to run, like sample inputs or expected outputs. In Go, you put these files in a folder named testdata right next to your test file. The Go test runner automatically includes this folder so your tests can read the files without you needing to copy them or change your build settings.