1 files changed, 118 insertions, 0 deletions
diff --git a/ancestor/unit_test.go b/ancestor/unit_test.go
new file mode 100644
index 00000000..827aeb8f
--- /dev/null
+++ b/ancestor/unit_test.go
@@ -0,0 +1,118 @@
+package ancestor_test
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+
+	giterrors "codeberg.org/lindenii/furgit/errors"
+	"codeberg.org/lindenii/furgit/internal/testgit"
+	"codeberg.org/lindenii/furgit/object"
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/objectstore/memory"
+	"codeberg.org/lindenii/furgit/objecttype"
+
+	"codeberg.org/lindenii/furgit/ancestor"
+)
+
+// commitBody serializes one minimal commit body.
+func commitBody(tree objectid.ObjectID, parents ...objectid.ObjectID) []byte {
+	buf := fmt.Appendf(nil, "tree %s\n", tree.String())
+	for _, parent := range parents {
+		buf = append(buf, fmt.Appendf(nil, "parent %s\n", parent.String())...)
+	}
+
+	buf = append(buf, []byte("\nmsg\n")...)
+
+	return buf
+}
+
+// tagBody serializes one minimal annotated tag body.
+func tagBody(target objectid.ObjectID, targetType objecttype.Type) []byte {
+	targetName, ok := objecttype.Name(targetType)
+	if !ok {
+		panic("invalid tag target type")
+	}
+
+	return fmt.Appendf(nil, "object %s\ntype %s\ntag t\n\nmsg\n", target.String(), targetName)
+}
+
+// mustSerializeTree serializes one tree or fails the test.
+func mustSerializeTree(tb testing.TB, tree *object.Tree) []byte {
+	tb.Helper()
+
+	body, err := tree.SerializeWithoutHeader()
+	if err != nil {
+		tb.Fatalf("SerializeWithoutHeader: %v", err)
+	}
+
+	return body
+}
+
+func TestIs(t *testing.T) {
+	t.Parallel()
+
+	testgit.ForEachAlgorithm(t, func(t *testing.T, algo objectid.Algorithm) { //nolint:thelper
+		store := memory.New(algo)
+		blob := store.AddObject(objecttype.TypeBlob, []byte("blob\n"))
+		tree := store.AddObject(objecttype.TypeTree, mustSerializeTree(t, &object.Tree{Entries: []object.TreeEntry{{
+			Mode: object.FileModeRegular,
+			Name: []byte("f"),
+			ID:   blob,
+		}}}))
+		c1 := store.AddObject(objecttype.TypeCommit, commitBody(tree))
+		c2 := store.AddObject(objecttype.TypeCommit, commitBody(tree, c1))
+		otherBlob := store.AddObject(objecttype.TypeBlob, []byte("other-blob\n"))
+		otherTree := store.AddObject(objecttype.TypeTree, mustSerializeTree(t, &object.Tree{Entries: []object.TreeEntry{{
+			Mode: object.FileModeRegular,
+			Name: []byte("g"),
+			ID:   otherBlob,
+		}}}))
+		c3 := store.AddObject(objecttype.TypeCommit, commitBody(otherTree))
+		tag := store.AddObject(objecttype.TypeTag, tagBody(c2, objecttype.TypeCommit))
+
+		ok, err := ancestor.Is(store, nil, c1, tag)
+		if err != nil {
+			t.Fatalf("Is(c1, tag): %v", err)
+		}
+
+		if !ok {
+			t.Fatal("expected c1 to be ancestor of tag->c2")
+		}
+
+		ok, err = ancestor.Is(store, nil, c3, c2)
+		if err != nil {
+			t.Fatalf("Is(c3, c2): %v", err)
+		}
+
+		if ok {
+			t.Fatal("did not expect c3 to be ancestor of c2")
+		}
+	})
+}
+
+func TestIsRejectsNonCommitAfterPeel(t *testing.T) {
+	t.Parallel()
+
+	testgit.ForEachAlgorithm(t, func(t *testing.T, algo objectid.Algorithm) { //nolint:thelper
+		store := memory.New(algo)
+		blob := store.AddObject(objecttype.TypeBlob, []byte("blob\n"))
+		tree := store.AddObject(objecttype.TypeTree, mustSerializeTree(t, &object.Tree{Entries: []object.TreeEntry{{
+			Mode: object.FileModeRegular,
+			Name: []byte("f"),
+			ID:   blob,
+		}}}))
+		commit := store.AddObject(objecttype.TypeCommit, commitBody(tree))
+		tagToTree := store.AddObject(objecttype.TypeTag, tagBody(tree, objecttype.TypeTree))
+
+		_, err := ancestor.Is(store, nil, commit, tagToTree)
+		if err == nil {
+			t.Fatal("expected error")
+		}
+
+		var typeErr *giterrors.ObjectTypeError
+		if !errors.As(err, &typeErr) {
+			t.Fatalf("expected ObjectTypeError, got %T (%v)", err, err)
+		}
+	})
+}