sessionctx/variable: fix incorrect parallel tests (#27981)

sessionctx/variable/session_test.go

@@ -34,6 +34,7 @@ func TestSetSystemVariable(t *testing.T) {
 	v := variable.NewSessionVars()
 	v.GlobalVarsAccessor = variable.NewMockGlobalAccessor()
 	v.TimeZone = time.UTC
+
 	testCases := []struct {
 		key   string
 		value string
@@ -53,9 +54,9 @@ func TestSetSystemVariable(t *testing.T) {
 		{variable.TiDBMemQuotaApplyCache, "1024", false},
 		{variable.TiDBEnableStmtSummary, "1", false},
 	}
+
 	for _, tc := range testCases {
 		t.Run(tc.key, func(t *testing.T) {
-			t.Parallel()
 			err := variable.SetSessionSystemVar(v, tc.key, tc.value)
 			if tc.err {
 				require.Error(t, err)

sessionctx/variable/statusvar_test.go

@@ -20,17 +20,6 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-type mockStatusVarSuite struct {
-	ms *mockStatistics
-}
-
-func createStatusVarSuite(t *testing.T) (s *mockStatusVarSuite) {
-	s = new(mockStatusVarSuite)
-	s.ms = &mockStatistics{}
-	RegisterStatistics(s.ms)
-	return
-}
-
 // mockStatistics represents mocked statistics.
 type mockStatistics struct{}
 
@@ -53,18 +42,20 @@ func (ms *mockStatistics) GetScope(status string) ScopeFlag {
 	return scope
 }
 
-func (ms *mockStatistics) Stats(vars *SessionVars) (map[string]interface{}, error) {
+func (ms *mockStatistics) Stats(_ *SessionVars) (map[string]interface{}, error) {
 	m := make(map[string]interface{}, len(specificStatusScopes))
 	m[testStatus] = testStatusVal
 
 	return m, nil
 }
 
 func TestStatusVar(t *testing.T) {
-	s := createStatusVarSuite(t)
-	scope := s.ms.GetScope(testStatus)
+	ms := &mockStatistics{}
+	RegisterStatistics(ms)
+
+	scope := ms.GetScope(testStatus)
 	require.Equal(t, DefaultStatusVarScopeFlag, scope)
-	scope = s.ms.GetScope(testSessionStatus)
+	scope = ms.GetScope(testSessionStatus)
 	require.Equal(t, ScopeSession, scope)
 
 	vars, err := GetStatusVars(nil)