add test

Signed-off-by: Patrick Zheng <[email protected]>

request.go

@@ -28,6 +28,9 @@ import (
 	"github.com/notaryproject/tspclient-go/internal/oid"
 )
 
+// nonceGenerator generates nonce. Used for unit test
+var nonceGenerator func() (*big.Int, error) = generateNonce
+
 // MessageImprint contains the hash of the datum to be time-stamped.
 //
 //	MessageImprint ::= SEQUENCE {
@@ -121,7 +124,7 @@ func NewRequest(opts RequestOptions) (*Request, error) {
 	if tspclientasn1.EqualRawValue(hashAlgParameter, asn1.RawValue{}) || tspclientasn1.EqualRawValue(hashAlgParameter, asn1.NullRawValue) {
 		hashAlgParameter = asn1NullRawValue
 	}
-	nonce, err := generateNonce()
+	nonce, err := nonceGenerator()
 	if err != nil {
 		return nil, &MalformedRequestError{Msg: err.Error()}
 	}

request_test.go

@@ -19,6 +19,7 @@ import (
 	"encoding/asn1"
 	"errors"
 	"fmt"
+	"math/big"
 	"reflect"
 	"testing"
 
@@ -71,6 +72,21 @@ func TestNewRequest(t *testing.T) {
 	if !reflect.DeepEqual(req.MessageImprint.HashAlgorithm.Parameters, asn1NullRawValue) {
 		t.Fatalf("expected %v, but got %v", asn1NullRawValue, req.MessageImprint.HashAlgorithm.Parameters)
 	}
+
+	nonceGenerator = func() (*big.Int, error) {
+		return nil, errors.New("failed to generate nonce")
+	}
+	opts = RequestOptions{
+		Content:       message,
+		HashAlgorithm: crypto.SHA256,
+	}
+	expectedErrMsg = "malformed timestamping request: failed to generate nonce"
+	_, err = NewRequest(opts)
+	if err == nil || !errors.As(err, &malformedRequest) || err.Error() != expectedErrMsg {
+		t.Fatalf("expected error %s, but got %v", expectedErrMsg, err)
+	}
+	// clean up
+	nonceGenerator = generateNonce
 }
 
 func TestRequestMarshalBinary(t *testing.T) {