1 files changed, 133 insertions, 0 deletions
diff --git a/ancestor/integration_test.go b/ancestor/integration_test.go
new file mode 100644
index 00000000..d13c86ed
--- /dev/null
+++ b/ancestor/integration_test.go
@@ -0,0 +1,133 @@
+package ancestor_test
+
+import (
+	"errors"
+	"testing"
+
+	giterrors "codeberg.org/lindenii/furgit/errors"
+	"codeberg.org/lindenii/furgit/internal/testgit"
+	"codeberg.org/lindenii/furgit/objectid"
+
+	"codeberg.org/lindenii/furgit/ancestor"
+)
+
+func TestIsMatchesGitMergeBase(t *testing.T) {
+	t.Parallel()
+
+	testgit.ForEachAlgorithm(t, func(t *testing.T, algo objectid.Algorithm) { //nolint:thelper
+		testRepo := testgit.NewRepo(t, testgit.RepoOptions{
+			ObjectFormat: algo,
+			Bare:         true,
+			RefFormat:    "files",
+		})
+
+		_, tree1 := testRepo.MakeSingleFileTree(t, "one.txt", []byte("one\n"))
+		c1 := testRepo.CommitTree(t, tree1, "c1")
+
+		_, tree2 := testRepo.MakeSingleFileTree(t, "two.txt", []byte("two\n"))
+		c2 := testRepo.CommitTree(t, tree2, "c2", c1)
+
+		_, tree3 := testRepo.MakeSingleFileTree(t, "three.txt", []byte("three\n"))
+		c3 := testRepo.CommitTree(t, tree3, "c3", c2)
+
+		tag := testRepo.TagAnnotated(t, "tip", c2, "tip")
+
+		store := testRepo.OpenObjectStore(t)
+
+		got, err := ancestor.Is(store, nil, c1, tag)
+		if err != nil {
+			t.Fatalf("Is(c1, tag): %v", err)
+		}
+
+		want := gitMergeBaseIsAncestor(t, testRepo, c1, c2)
+		if got != want {
+			t.Fatalf("Is(c1, tag)=%v, want %v", got, want)
+		}
+
+		got, err = ancestor.Is(store, nil, c3, c2)
+		if err != nil {
+			t.Fatalf("Is(c3, c2): %v", err)
+		}
+
+		want = gitMergeBaseIsAncestor(t, testRepo, c3, c2)
+		if got != want {
+			t.Fatalf("Is(c3, c2)=%v, want %v", got, want)
+		}
+	})
+}
+
+func TestIsMatchesGitMergeBaseWithCommitGraph(t *testing.T) {
+	t.Parallel()
+
+	testgit.ForEachAlgorithm(t, func(t *testing.T, algo objectid.Algorithm) { //nolint:thelper
+		testRepo := testgit.NewRepo(t, testgit.RepoOptions{
+			ObjectFormat: algo,
+			Bare:         true,
+			RefFormat:    "files",
+		})
+
+		_, tree1 := testRepo.MakeSingleFileTree(t, "one.txt", []byte("one\n"))
+		c1 := testRepo.CommitTree(t, tree1, "c1")
+
+		_, tree2 := testRepo.MakeSingleFileTree(t, "two.txt", []byte("two\n"))
+		c2 := testRepo.CommitTree(t, tree2, "c2", c1)
+
+		testRepo.UpdateRef(t, "refs/heads/main", c2)
+		testRepo.SymbolicRef(t, "HEAD", "refs/heads/main")
+		testRepo.CommitGraphWrite(t, "--reachable")
+
+		store := testRepo.OpenObjectStore(t)
+		graph := testRepo.OpenCommitGraph(t)
+
+		got, err := ancestor.Is(store, graph, c1, c2)
+		if err != nil {
+			t.Fatalf("Is(c1, c2): %v", err)
+		}
+
+		want := gitMergeBaseIsAncestor(t, testRepo, c1, c2)
+		if got != want {
+			t.Fatalf("Is(c1, c2)=%v, want %v", got, want)
+		}
+	})
+}
+
+func TestIsMissingObject(t *testing.T) {
+	t.Parallel()
+
+	testgit.ForEachAlgorithm(t, func(t *testing.T, algo objectid.Algorithm) { //nolint:thelper
+		testRepo := testgit.NewRepo(t, testgit.RepoOptions{
+			ObjectFormat: algo,
+			Bare:         true,
+			RefFormat:    "files",
+		})
+
+		_, treeID, commitID := testRepo.MakeCommit(t, "missing")
+
+		testRepo.RemoveLooseObject(t, treeID)
+
+		store := testRepo.OpenObjectStore(t)
+
+		_, err := ancestor.Is(store, nil, treeID, commitID)
+		if err == nil {
+			t.Fatal("expected error")
+		}
+
+		var missing *giterrors.ObjectMissingError
+		if !errors.As(err, &missing) {
+			t.Fatalf("expected ObjectMissingError, got %T (%v)", err, err)
+		}
+
+		if missing.OID != treeID {
+			t.Fatalf("missing oid = %s, want %s", missing.OID, treeID)
+		}
+	})
+}
+
+// gitMergeBaseIsAncestor reports Git's merge-base ancestry answer.
+func gitMergeBaseIsAncestor(t *testing.T, testRepo *testgit.TestRepo, left, right objectid.ObjectID) bool {
+	t.Helper()
+
+	out := testRepo.Run(t, "merge-base", left.String(), right.String())
+
+	return out == left.String()
+}