timer/test: Improve test coverage

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/morph/timer/block_test.go

@@ -1,6 +1,7 @@
 package timer_test
 
 import (
+	"errors"
 	"testing"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/morph/timer"
@@ -48,6 +49,38 @@ func TestIRBlockTimer_Reset(t *testing.T) {
 	require.Equal(t, baseCounter[0], baseCounter[1])
 }
 
+func TestBlockTimer_ResetChangeDuration(t *testing.T) {
+	var dur uint32 = 2
+	var err error
+	var counter int
+
+	bt := timer.NewBlockTimer(
+		func() (uint32, error) { return dur, err },
+		func() { counter++ })
+
+	require.NoError(t, bt.Reset())
+
+	tickN(bt, 2)
+	require.Equal(t, 1, counter)
+
+	t.Run("return error", func(t *testing.T) {
+		dur = 5
+		err = errors.New("my awesome error")
+		require.ErrorIs(t, bt.Reset(), err)
+
+		tickN(bt, 2)
+		require.Equal(t, 2, counter)
+	})
+	t.Run("change duration", func(t *testing.T) {
+		dur = 5
+		err = nil
+		require.NoError(t, bt.Reset())
+
+		tickN(bt, 5)
+		require.Equal(t, 3, counter)
+	})
+}
+
 func TestBlockTimer(t *testing.T) {
 	blockDur := uint32(10)
 	baseCallCounter := uint32(0)