Add some repcluster handling to audit and add some tests (#2384)

* Add some repcluster handling to audit and add some tests

* Fix incorrect assumption about nil auth

audit/format_test.go

@@ -0,0 +1,55 @@
+package audit
+
+import (
+	"io"
+	"io/ioutil"
+	"testing"
+
+	"github.com/hashicorp/vault/helper/salt"
+	"github.com/hashicorp/vault/logical"
+)
+
+type noopFormatWriter struct {
+}
+
+func (n *noopFormatWriter) WriteRequest(_ io.Writer, _ *AuditRequestEntry) error {
+	return nil
+}
+
+func (n *noopFormatWriter) WriteResponse(_ io.Writer, _ *AuditResponseEntry) error {
+	return nil
+}
+
+func TestFormatRequestErrors(t *testing.T) {
+	salter, _ := salt.NewSalt(nil, nil)
+	config := FormatterConfig{
+		Salt: salter,
+	}
+	formatter := AuditFormatter{
+		AuditFormatWriter: &noopFormatWriter{},
+	}
+
+	if err := formatter.FormatRequest(ioutil.Discard, config, nil, nil, nil); err == nil {
+		t.Fatal("expected error due to nil request")
+	}
+	if err := formatter.FormatRequest(nil, config, nil, &logical.Request{}, nil); err == nil {
+		t.Fatal("expected error due to nil writer")
+	}
+}
+
+func TestFormatResponseErrors(t *testing.T) {
+	salter, _ := salt.NewSalt(nil, nil)
+	config := FormatterConfig{
+		Salt: salter,
+	}
+	formatter := AuditFormatter{
+		AuditFormatWriter: &noopFormatWriter{},
+	}
+
+	if err := formatter.FormatResponse(ioutil.Discard, config, nil, nil, nil, nil); err == nil {
+		t.Fatal("expected error due to nil request")
+	}
+	if err := formatter.FormatResponse(nil, config, nil, &logical.Request{}, nil, nil); err == nil {
+		t.Fatal("expected error due to nil writer")
+	}
+}