v0.19.1 dep update, test helper package

internal/testutil/fixtures.go

@@ -0,0 +1,31 @@
+// Package testutil provides standard-library fixtures shared by logwisp tests.
+// Application packages must not import it.
+package testutil
+
+import (
+	"os"
+	"strings"
+	"testing"
+)
+
+// ClearEnvPrefix isolates overrides while preserving the caller's environment.
+// Like testing.Setenv, it must not be used by parallel tests.
+func ClearEnvPrefix(t testing.TB, prefix string) {
+	t.Helper()
+	for _, entry := range os.Environ() {
+		key, value, _ := strings.Cut(entry, "=")
+		if strings.HasPrefix(key, prefix) {
+			t.Setenv(key, value) // Register restoration before unsetting it.
+			if err := os.Unsetenv(key); err != nil {
+				t.Fatalf("unset fixture variable %s: %v", key, err)
+			}
+		}
+	}
+}
+
+func WriteFile(t testing.TB, path, contents string) {
+	t.Helper()
+	if err := os.WriteFile(path, []byte(contents), 0600); err != nil {
+		t.Fatalf("write fixture %q: %v", path, err)
+	}
+}