Add test file handling helpers

internal/utils/testing/tempfile.go

@@ -0,0 +1,46 @@
+package testutils
+
+import (
+	"io"
+	"io/ioutil"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/pkg/errors"
+)
+
+// NewTempFile creates a new, empty temp file for testing.  Errors are fatal.
+func NewTempFile(t *testing.T) *os.File {
+	pattern := strings.ReplaceAll(t.Name(), string(os.PathSeparator), "_")
+	f, err := ioutil.TempFile("", pattern)
+	if err != nil {
+		t.Fatal(errors.Wrap(err, "cannot create temp file"))
+	}
+	return f
+}
+
+// NewTempFileWithContents creates a new, empty temp file for testing,
+// with the given contents.  The read/write offset is set to the beginning.
+// Errors are fatal.
+func NewTempFileWithContents(t *testing.T, contents []byte) *os.File {
+	f := NewTempFile(t)
+	if _, err := f.Write(contents); err != nil {
+		t.Fatal(errors.Wrapf(err, "cannot write contents into %s", f.Name()))
+	}
+	if _, err := f.Seek(0, io.SeekStart); err != nil {
+		t.Fatal(errors.Wrapf(err, "cannot rewind test file %s", f.Name()))
+	}
+	return f
+}
+
+// CloseAndRemoveTempFile closes/removes the temp file.  Errors are logged.
+func CloseAndRemoveTempFile(t *testing.T, f *os.File) {
+	fn := f.Name()
+	if err := f.Close(); err != nil {
+		t.Log(errors.Wrapf(err, "cannot close test file %s", fn))
+	}
+	if err := os.Remove(fn); err != nil {
+		t.Log(errors.Wrapf(err, "cannot remove test file %s", fn))
+	}
+}