chore: clean up tests (#37715)

1. use MockVariableValue as much as possible
2. use wg.Go as much as possible instead of Add/Done
3. simplify global lock's DefaultLocker logic to make it easier to test
4. introduce a general approach for getting external service config in
CI
5. remove unclear & unnecessary "t.Skip"
6. use modern generic syntax for remaining "DecodeJSON" calls
7. clarify test result for "list gitignore templates" and "list
licenses"

modules/test/utils.go

@@ -11,7 +11,10 @@ import (
 	"io"
 	"net/http"
 	"net/http/httptest"
+	"os"
+	"strconv"
 	"strings"
+	"sync"
 
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/util"
@@ -141,3 +144,41 @@ func CompressGzip(content string) *bytes.Buffer {
 	_ = cw.Close()
 	return buf
 }
+
+var AllowSkipExternalService = sync.OnceValue(func() bool {
+	isLocalTesting := os.Getenv("CI") == ""
+	ciSkipExternal, _ := strconv.ParseBool(os.Getenv("GITEA_TEST_CI_SKIP_EXTERNAL"))
+	return isLocalTesting || ciSkipExternal
+})
+
+type TestingT interface {
+	Helper()
+	Skipf(format string, args ...any)
+	Errorf(format string, args ...any)
+	Fatalf(format string, args ...any)
+}
+
+func ExternalServiceHTTP(t TestingT, envVarName, def string) string {
+	t.Helper()
+	val := util.IfZero(os.Getenv(envVarName), def)
+	if val == "" {
+		if AllowSkipExternalService() {
+			t.Skipf("skipping test because %s is not set", envVarName)
+		} else {
+			t.Fatalf("%s is not set, but skipping is not allowed in CI", envVarName)
+		}
+	}
+	// minio's endpoint is "host:port" pattern
+	testURL := util.Iif(strings.Contains(val, "://"), val, "http://"+val)
+	resp, err := http.Get(testURL)
+	if err != nil {
+		if AllowSkipExternalService() {
+			t.Skipf("skipping test because %s is not ready", val)
+		} else {
+			t.Fatalf("%s is not ready, but skipping is not allowed in CI", val)
+		}
+	} else {
+		_ = resp.Body.Close()
+	}
+	return val
+}