test: transaction splitting (#813)

Define unit tests for transaction splitting. These should be helpful
when we tackle celestiaorg/celestia-app#802

pkg/shares/share_splitting_test.go

@@ -0,0 +1,98 @@
+package shares
+
+import (
+	"bytes"
+	"reflect"
+	"testing"
+
+	coretypes "github.com/tendermint/tendermint/types"
+)
+
+func TestSplitTxs(t *testing.T) {
+	type testCase struct {
+		name string
+		txs  coretypes.Txs
+		want [][]byte
+	}
+	testCases := []testCase{
+		{
+			name: "empty txs",
+			txs:  coretypes.Txs{},
+			want: [][]byte{},
+		},
+		{
+			name: "one small tx",
+			txs:  coretypes.Txs{coretypes.Tx{0xa}},
+			want: [][]uint8{
+				append([]uint8{
+					0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, // namespace id
+					0x1, // info byte
+					0x0, // reserved byte
+					0x1, // unit length of first transaction
+					0xa, // data of first transaction
+				}, bytes.Repeat([]byte{0}, 244)...), // padding
+			},
+		},
+		{
+			name: "two small txs",
+			txs:  coretypes.Txs{coretypes.Tx{0xa}, coretypes.Tx{0xb}},
+			want: [][]uint8{
+				append([]uint8{
+					0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, // namespace id
+					0x1, // info byte
+					0x0, // reserved byte
+					0x1, // unit length of first transaction
+					0xa, // data of first transaction
+					0x1, // unit length of second transaction
+					0xb, // data of second transaction
+				}, bytes.Repeat([]byte{0}, 242)...), // padding
+			},
+		},
+		{
+			name: "one large tx that spans two shares",
+			txs:  coretypes.Txs{bytes.Repeat([]byte{0xC}, 245)},
+			want: [][]uint8{
+				append([]uint8{
+					0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, // namespace id
+					0x1,    // info byte
+					0x0,    // BUG reserved byte should be non-zero see https://github.com/celestiaorg/celestia-app/issues/802
+					245, 1, // unit length of first transaction is 245
+				}, bytes.Repeat([]byte{0xc}, 244)...), // data of first transaction
+				append([]uint8{
+					0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, // namespace id
+					0x0, // info byte
+					0x0, // reserved byte
+					0xc, // continuation data of first transaction
+				}, bytes.Repeat([]byte{0x0}, 245)...), // padding
+			},
+		},
+		{
+			name: "one small tx then one large tx that spans two shares",
+			txs:  coretypes.Txs{coretypes.Tx{0xd}, bytes.Repeat([]byte{0xe}, 243)},
+			want: [][]uint8{
+				append([]uint8{
+					0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, // namespace id
+					0x1,    // info byte
+					0x0,    // BUG reserved byte should be non-zero see https://github.com/celestiaorg/celestia-app/issues/802
+					1,      // unit length of first transaction
+					0xd,    // data of first transaction
+					243, 1, // unit length of second transaction is 243
+				}, bytes.Repeat([]byte{0xe}, 242)...), // data of first transaction
+				append([]uint8{
+					0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, // namespace id
+					0x0, // info byte
+					0x0, // reserved byte
+					0xe, // continuation data of second transaction
+				}, bytes.Repeat([]byte{0x0}, 245)...), // padding
+			},
+		},
+	}
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			got := SplitTxs(tt.txs)
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("SplitTxs(%#v) got %#v, want %#v", tt.txs, got, tt.want)
+			}
+		})
+	}
+}