1 files changed, 160 insertions, 0 deletions
diff --git a/internal/format/packrev/packrev_test.go b/internal/format/packrev/packrev_test.go
new file mode 100644
index 00000000..b644e15e
--- /dev/null
+++ b/internal/format/packrev/packrev_test.go
@@ -0,0 +1,160 @@
+package packrev_test
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"os"
+	"testing"
+
+	"lindenii.org/go/furgit/internal/format/packidx"
+	"lindenii.org/go/furgit/internal/format/packrev"
+	"lindenii.org/go/furgit/object/id"
+)
+
+func TestParseGitReverseIndex(t *testing.T) {
+	t.Parallel()
+
+	for _, objectFormat := range id.SupportedObjectFormats() {
+		t.Run(objectFormat.String(), func(t *testing.T) {
+			t.Parallel()
+
+			prefix := makeGitPack(t, objectFormat)
+
+			revData, err := os.ReadFile(prefix + ".rev") //nolint:gosec
+			if err != nil {
+				t.Fatalf("ReadFile: %v", err)
+			}
+
+			rev, err := packrev.Parse(revData, objectFormat)
+			if err != nil {
+				t.Fatalf("Parse: %v", err)
+			}
+
+			idxData, err := os.ReadFile(prefix + ".idx") //nolint:gosec
+			if err != nil {
+				t.Fatalf("ReadFile: %v", err)
+			}
+
+			idx, err := packidx.Parse(idxData, objectFormat.Size())
+			if err != nil {
+				t.Fatalf("packidx.Parse: %v", err)
+			}
+
+			if rev.NumObjects() != idx.NumObjects() {
+				t.Fatalf("NumObjects = %d, want %d", rev.NumObjects(), idx.NumObjects())
+			}
+
+			packData, err := os.ReadFile(prefix + ".pack") //nolint:gosec
+			if err != nil {
+				t.Fatalf("ReadFile: %v", err)
+			}
+
+			packTrailer := packData[len(packData)-objectFormat.Size():]
+			if !bytes.Equal(rev.PackHash(), packTrailer) {
+				t.Fatalf("PackHash does not match pack trailer")
+			}
+
+			want := packOrderPositions(t, &idx)
+
+			for packOrder, wantPosition := range want {
+				position, err := rev.PositionAt(packOrder)
+				if err != nil {
+					t.Fatalf("PositionAt(%d): %v", packOrder, err)
+				}
+
+				if position != int(wantPosition) {
+					t.Fatalf("PositionAt(%d) = %d, want %d", packOrder, position, wantPosition)
+				}
+			}
+		})
+	}
+}
+
+func TestParseMalformed(t *testing.T) {
+	t.Parallel()
+
+	for _, objectFormat := range id.SupportedObjectFormats() {
+		t.Run(objectFormat.String(), func(t *testing.T) {
+			t.Parallel()
+
+			valid := writeSyntheticRev(t, objectFormat, []uint32{2, 0, 1, 3})
+
+			corrupt := func(mutate func(data []byte) []byte) []byte {
+				return mutate(bytes.Clone(valid))
+			}
+
+			cases := []struct {
+				name string
+				data []byte
+			}{
+				{name: "empty", data: []byte{}},
+				{name: "truncated", data: corrupt(func(d []byte) []byte { return d[:10] })},
+				{
+					name: "bad signature",
+					data: corrupt(func(d []byte) []byte {
+						d[0] ^= 0xff
+
+						return d
+					}),
+				},
+				{
+					name: "bad version",
+					data: corrupt(func(d []byte) []byte {
+						d[7] = 2
+
+						return d
+					}),
+				},
+				{
+					name: "hash function mismatch",
+					data: corrupt(func(d []byte) []byte {
+						d[11] ^= 0xff
+
+						return d
+					}),
+				},
+				{
+					name: "position table size not 32-bit multiple",
+					data: corrupt(func(d []byte) []byte { return append(d, 0xde, 0xad) }),
+				},
+			}
+
+			for _, tc := range cases {
+				t.Run(tc.name, func(t *testing.T) {
+					t.Parallel()
+
+					_, err := packrev.Parse(tc.data, objectFormat)
+					if !errors.Is(err, packrev.ErrMalformedReverseIndex) {
+						t.Fatalf("Parse error = %v, want ErrMalformedReverseIndex", err)
+					}
+				})
+			}
+		})
+	}
+}
+
+func TestPositionAtMalformed(t *testing.T) {
+	t.Parallel()
+
+	for _, objectFormat := range id.SupportedObjectFormats() {
+		t.Run(objectFormat.String(), func(t *testing.T) {
+			t.Parallel()
+
+			data := writeSyntheticRev(t, objectFormat, []uint32{2, 0, 1, 3})
+
+			// Corrupt the first stored position to one past the object count.
+			binary.BigEndian.PutUint32(data[12:], 4)
+
+			rev, err := packrev.Parse(data, objectFormat)
+			if err != nil {
+				t.Fatalf("Parse: %v", err)
+			}
+
+			_, err = rev.PositionAt(0)
+			if !errors.Is(err, packrev.ErrMalformedReverseIndex) {
+				t.Fatalf("PositionAt error = %v, want ErrMalformedReverseIndex", err)
+			}
+		})
+	}
+}