package config

import (
	"os"
	"strings"
	"testing"
)

// ClearEnvForTest unsets every variable in the process environment
// for the rest of the test and puts each back when the test ends, so
// a test sees only the variables it sets itself, not whatever the
// developer's shell exports.
func ClearEnvForTest(t *testing.T) {
	t.Helper()

	for _, entry := range os.Environ() {
		key, _, _ := strings.Cut(entry, "=")

		// t.Setenv registers the restore; the Unsetenv after it is
		// what makes the key absent, since a key set to the empty
		// string is still present, and godotenv will not overwrite a
		// present key.
		t.Setenv(key, "")

		err := os.Unsetenv(key)
		if err != nil {
			t.Fatalf("unsetting %s: %v", key, err)
		}
	}
}