hooks: add null logger test

hooks/null/null_test.go

@@ -0,0 +1,19 @@
+package null
+
+import (
+	"github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestNullLogger(t *testing.T) {
+	logger, hook := NewNullLogger()
+	logger.Error("Helloerror")
+
+	assert.Equal(t, 1, len(hook.Entries))
+	assert.Equal(t, logrus.ErrorLevel, hook.LastEntry().Level)
+	assert.Equal(t, "Helloerror", hook.LastEntry().Message)
+
+	hook.Reset()
+	assert.Nil(t, hook.LastEntry())
+}