diff --git a/core/fs/files_test.go b/core/fs/files_test.go
new file mode 100644
index 00000000..96ff174e
--- /dev/null
+++ b/core/fs/files_test.go
@@ -0,0 +1,15 @@
+package fs
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCloseOnExec(t *testing.T) {
+	file := os.NewFile(0, os.DevNull)
+	assert.NotPanics(t, func() {
+		CloseOnExec(file)
+	})
+}
diff --git a/core/stat/alert_test.go b/core/stat/alert_test.go
index c5419698..0e95afb3 100644
--- a/core/stat/alert_test.go
+++ b/core/stat/alert_test.go
@@ -4,6 +4,7 @@
 package stat
 
 import (
+	"os"
 	"strconv"
 	"sync/atomic"
 	"testing"
@@ -12,6 +13,9 @@ import (
 )
 
 func TestReport(t *testing.T) {
+	os.Setenv(clusterNameKey, "test-cluster")
+	defer os.Unsetenv(clusterNameKey)
+
 	var count int32
 	SetReporter(func(s string) {
 		atomic.AddInt32(&count, 1)
diff --git a/zrpc/resolver/internal/directbuilder_test.go b/zrpc/resolver/internal/directbuilder_test.go
index e311fcba..b602ccdd 100644
--- a/zrpc/resolver/internal/directbuilder_test.go
+++ b/zrpc/resolver/internal/directbuilder_test.go
@@ -1,6 +1,7 @@
 package internal
 
 import (
+	"errors"
 	"fmt"
 	"net/url"
 	"strconv"
@@ -35,10 +36,17 @@ func TestDirectBuilder_Build(t *testing.T) {
 			target := fmt.Sprintf("%s:///%s", DirectScheme, strings.Join(servers, ","))
 			uri, err := url.Parse(target)
 			assert.Nil(t, err)
+			cc.err = errors.New("foo")
 			_, err = b.Build(resolver.Target{
 				URL: *uri,
 			}, cc, resolver.BuildOptions{})
-			assert.Nil(t, err)
+			assert.NotNil(t, err)
+			cc.err = nil
+			_, err = b.Build(resolver.Target{
+				URL: *uri,
+			}, cc, resolver.BuildOptions{})
+			assert.NoError(t, err)
+
 			size := mathx.MinInt(test, subsetSize)
 			assert.Equal(t, size, len(cc.state.Addresses))
 			m := make(map[string]lang.PlaceholderType)
diff --git a/zrpc/resolver/internal/resolver_test.go b/zrpc/resolver/internal/resolver_test.go
index dde4065a..2f4a4690 100644
--- a/zrpc/resolver/internal/resolver_test.go
+++ b/zrpc/resolver/internal/resolver_test.go
@@ -16,11 +16,12 @@ func TestNopResolver(t *testing.T) {
 
 type mockedClientConn struct {
 	state resolver.State
+	err   error
 }
 
 func (m *mockedClientConn) UpdateState(state resolver.State) error {
 	m.state = state
-	return nil
+	return m.err
 }
 
 func (m *mockedClientConn) ReportError(err error) {