package errs

import "testing"

// AssertErrorContains 检查错误是否包含预期子字符串
// 用于替代脆弱的直接字符串匹配
func AssertErrorContains(t *testing.T, err error, wantSubstring string) {
	t.Helper()
	if err == nil {
		t.Fatalf("expected error containing %q, got nil", wantSubstring)
	}
	if !containsSubstring(err.Error(), wantSubstring) {
		t.Fatalf("error = %q, want containing %q", err.Error(), wantSubstring)
	}
}

func containsSubstring(s, substr string) bool {
	return len(substr) <= len(s) && containsAt(s, substr, 0)
}

func containsAt(s, substr string, start int) bool {
	for i := start; i <= len(s)-len(substr); i++ {
		if s[i:i+len(substr)] == substr {
			return true
		}
	}
	return false
}