hooks: add a null logger for the lower-case import

README.md

@@ -434,15 +434,22 @@ Logrus has a built in facility for asserting the presence of log messages. This
 * a test logger (`test.NewNullLogger`) that just records log messages (and does not output any):
 
 ```go
-logger, hook := NewNullLogger()
+import (
-logger.Error("Hello error")
+  "testing"
+  "github.com/sirupsen/logrus/hooks/null"
+)
 
-assert.Equal(1, len(hook.Entries))
+func TestSomething(t *testing.T) {
-assert.Equal(logrus.ErrorLevel, hook.LastEntry().Level)
+  logger, hook := null.NewNullLogger()
-assert.Equal("Hello error", hook.LastEntry().Message)
+  logger.Error("Hello error")
 
-hook.Reset()
+  assert.Equal(1, len(hook.Entries))
-assert.Nil(hook.LastEntry())
+  assert.Equal(logrus.ErrorLevel, hook.LastEntry().Level)
+  assert.Equal("Hello error", hook.LastEntry().Message)
+
+  hook.Reset()
+  assert.Nil(hook.LastEntry())
+}
 ```
 
 #### Fatal handlers

hooks/null/null.go

@@ -0,0 +1,92 @@
+package null
+
+import (
+	"io/ioutil"
+	"sync"
+
+	"github.com/sirupsen/logrus"
+)
+
+// Hook is a hook designed for dealing with logs in test scenarios.
+type Hook struct {
+	// Entries is an array of all entries that have been received by this hook.
+	// For safe access, use the AllEntries() method, rather than reading this
+	// value directly.
+	Entries []*logrus.Entry
+	mu      sync.RWMutex
+}
+
+// NewGlobal installs a test hook for the global logger.
+func NewGlobal() *Hook {
+
+	hook := new(Hook)
+	logrus.AddHook(hook)
+
+	return hook
+
+}
+
+// NewLocal installs a test hook for a given local logger.
+func NewLocal(logger *logrus.Logger) *Hook {
+
+	hook := new(Hook)
+	logger.Hooks.Add(hook)
+
+	return hook
+
+}
+
+// NewNullLogger creates a discarding logger and installs the test hook.
+func NewNullLogger() (*logrus.Logger, *Hook) {
+
+	logger := logrus.New()
+	logger.Out = ioutil.Discard
+
+	return logger, NewLocal(logger)
+
+}
+
+func (t *Hook) Fire(e *logrus.Entry) error {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	t.Entries = append(t.Entries, e)
+	return nil
+}
+
+func (t *Hook) Levels() []logrus.Level {
+	return logrus.AllLevels
+}
+
+// LastEntry returns the last entry that was logged or nil.
+func (t *Hook) LastEntry() *logrus.Entry {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+	i := len(t.Entries) - 1
+	if i < 0 {
+		return nil
+	}
+	// Make a copy, for safety
+	e := *t.Entries[i]
+	return &e
+}
+
+// AllEntries returns all entries that were logged.
+func (t *Hook) AllEntries() []*logrus.Entry {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+	// Make a copy so the returned value won't race with future log requests
+	entries := make([]*logrus.Entry, len(t.Entries))
+	for i, entry := range t.Entries {
+		// Make a copy, for safety
+		e := *entry
+		entries[i] = &e
+	}
+	return entries
+}
+
+// Reset removes all Entries from this test hook.
+func (t *Hook) Reset() {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	t.Entries = make([]*logrus.Entry, 0)
+}