tests: Playing with Carbon Default is dangerous.

These variable are global. It has consequences.

People launching tests another timezone where facing random issues.
It was random because the tests are launched in different order on each run.

This was hidden by the CI forcing the timezone to PRC, and impossible to see by
someone working in PRC timezone.

Author: ccoVeille

database_unit_test.go

@@ -913,6 +913,8 @@ func TestCarbon_Issue240(t *testing.T) {
 
 // https://github.com/dromara/carbon/issues/243
 func TestCarbon_Issue243(t *testing.T) {
+	prepareTest(t)
+
 	SetDefault(Default{
 		Layout:       DateTimeLayout,
 		Timezone:     PRC,

default_bench_test.go

@@ -3,6 +3,8 @@ package carbon
 import "testing"
 
 func BenchmarkCarbon_SetDefault(b *testing.B) {
+	prepareTest(b)
+
 	d := Default{
 		Layout:       DateTimeLayout,
 		Timezone:     Local,

default_unit_test.go

@@ -7,6 +7,8 @@ import (
 )
 
 func TestCarbon_SetDefault(t *testing.T) {
+	prepareTest(t)
+
 	SetDefault(Default{
 		Layout:       DateTimeLayout,
 		Timezone:     PRC,

test.go

@@ -1,5 +1,9 @@
 package carbon
 
+import (
+	"testing"
+)
+
 // SetTestNow sets a test Carbon instance (real or mock) to be returned when a "now" instance is created.
 // 设置当前测试时间
 func (c *Carbon) SetTestNow(carbon Carbon) {
@@ -17,3 +21,19 @@ func (c *Carbon) UnSetTestNow() {
 func (c Carbon) IsSetTestNow() bool {
 	return c.testNow > 0
 }
+
+func prepareTest(tb testing.TB) {
+	tb.Helper()
+
+	// Store the current default
+	savedDefault := Default{
+		Layout:       defaultLayout,
+		Timezone:     defaultTimezone,
+		Locale:       defaultLocale,
+		WeekStartsAt: defaultWeekStartsAt,
+	}
+	tb.Cleanup(func() {
+		// restore the default when test is done
+		SetDefault(savedDefault)
+	})
+}