diff --git a/stream/stream_workers_test.go b/stream/stream_workers_test.go
new file mode 100644
index 00000000..ade284f2
--- /dev/null
+++ b/stream/stream_workers_test.go
@@ -0,0 +1,118 @@
+package stream
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/rusq/slack"
+	"github.com/stretchr/testify/assert"
+	"go.uber.org/mock/gomock"
+
+	"github.com/rusq/slackdump/v3/internal/fixtures"
+	"github.com/rusq/slackdump/v3/mocks/mock_processor"
+	"github.com/rusq/slackdump/v3/stream/mock_stream"
+)
+
+func TestStream_canvas(t *testing.T) {
+	testChannel := fixtures.Load[[]*slack.Channel](fixtures.TestChannels)[0]
+	type args struct {
+		ctx context.Context
+		// proc    processor.Conversations
+		channel *slack.Channel
+		fileId  string
+	}
+	tests := []struct {
+		name     string
+		fields   *Stream
+		args     args
+		expectFn func(ms *mock_stream.MockSlacker, mc *mock_processor.MockConversations)
+		wantErr  bool
+	}{
+		{
+			name:   "file ID is empty",
+			fields: &Stream{},
+			args: args{
+				ctx:     context.Background(),
+				channel: &slack.Channel{},
+				fileId:  "",
+			},
+			wantErr: false,
+		},
+		{
+			name:   "getfileinfocontext returns an error",
+			fields: &Stream{},
+			args: args{
+				ctx:    context.Background(),
+				fileId: "F123456",
+			},
+			expectFn: func(ms *mock_stream.MockSlacker, mc *mock_processor.MockConversations) {
+				ms.EXPECT().GetFileInfoContext(gomock.Any(), "F123456", 0, 1).Return(nil, nil, nil, errors.New("getfileinfocontext error"))
+			},
+			wantErr: true,
+		},
+		{
+			name:   "file not found",
+			fields: &Stream{},
+			args: args{
+				ctx:    context.Background(),
+				fileId: "F123456",
+			},
+			expectFn: func(ms *mock_stream.MockSlacker, mc *mock_processor.MockConversations) {
+				ms.EXPECT().GetFileInfoContext(gomock.Any(), "F123456", 0, 1).Return(nil, nil, nil, nil)
+			},
+			wantErr: true,
+		},
+		{
+			name:   "success",
+			fields: &Stream{},
+			args: args{
+				ctx:     context.Background(),
+				channel: testChannel,
+				fileId:  "F123456",
+			},
+			expectFn: func(ms *mock_stream.MockSlacker, mc *mock_processor.MockConversations) {
+				ms.EXPECT().
+					GetFileInfoContext(gomock.Any(), "F123456", 0, 1).
+					Return(&slack.File{ID: "F123456"}, nil, nil, nil)
+				mc.EXPECT().
+					Files(gomock.Any(), testChannel, slack.Message{}, []slack.File{{ID: "F123456"}}).
+					Return(nil)
+			},
+			wantErr: false,
+		},
+		{
+			name:   "processor returns an error",
+			fields: &Stream{},
+			args: args{
+				ctx:     context.Background(),
+				channel: testChannel,
+				fileId:  "F123456",
+			},
+			expectFn: func(ms *mock_stream.MockSlacker, mc *mock_processor.MockConversations) {
+				ms.EXPECT().
+					GetFileInfoContext(gomock.Any(), "F123456", 0, 1).
+					Return(&slack.File{ID: "F123456"}, nil, nil, nil)
+				mc.EXPECT().
+					Files(gomock.Any(), testChannel, slack.Message{}, []slack.File{{ID: "F123456"}}).
+					Return(assert.AnError)
+			},
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ctrl := gomock.NewController(t)
+			ms := mock_stream.NewMockSlacker(ctrl)
+			mc := mock_processor.NewMockConversations(ctrl)
+			if tt.expectFn != nil {
+				tt.expectFn(ms, mc)
+			}
+			cs := tt.fields
+			cs.client = ms
+			if err := cs.canvas(tt.args.ctx, mc, tt.args.channel, tt.args.fileId); (err != nil) != tt.wantErr {
+				t.Errorf("Stream.canvas() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}