diff --git a/cmd/gendb/main.go b/cmd/gendb/main.go
index 9680540f..2787b7d0 100644
--- a/cmd/gendb/main.go
+++ b/cmd/gendb/main.go
@@ -12,6 +12,7 @@ import (
 	"log"
 
 	"golang.org/x/vulndb/internal/database"
+	"golang.org/x/vulndb/internal/gitrepo"
 )
 
 var (
@@ -23,7 +24,11 @@ var (
 func main() {
 	flag.Parse()
 	ctx := context.Background()
-	if err := database.Generate(ctx, *repoDir, *jsonDir, *indent); err != nil {
+	repo, err := gitrepo.CloneOrOpen(ctx, *repoDir)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if err := database.Generate(ctx, repo, *jsonDir, *indent); err != nil {
 		log.Fatal(err)
 	}
 }
diff --git a/internal/database/database.go b/internal/database/database.go
index 8565a5ae..0b90a2b9 100644
--- a/internal/database/database.go
+++ b/internal/database/database.go
@@ -73,7 +73,7 @@ const (
 // associated index maps). The result is an in-memory vulnerability database
 // that can be written to files via Database.Write.
 //
-// The repo must contain a "data/osv" folder to with files in
+// The repo must contain a "data/osv" folder with files in
 // OSV JSON format with filenames of the form GO-YYYY-XXXX.json.
 //
 // New does not modify the repo.
diff --git a/internal/database/generate.go b/internal/database/generate.go
index 70786d60..eb788bb7 100644
--- a/internal/database/generate.go
+++ b/internal/database/generate.go
@@ -7,28 +7,23 @@ package database
 import (
 	"context"
 
+	"github.com/go-git/go-git/v5"
 	"golang.org/x/vulndb/internal/derrors"
-	"golang.org/x/vulndb/internal/gitrepo"
 )
 
 // Generate creates and writes a new Go vulnerability database to outDir
-// based on the contents of the "data/osv" folder inside repoDir, a local
-// git repo.
+// based on the contents of the "data/osv" folder inside repo.
 //
-// repoDir must contain a "data/osv" folder to with files in
+// The repo must contain a "data/osv" folder with files in
 // OSV JSON format with filenames of the form GO-YYYY-XXXX.json.
-func Generate(ctx context.Context, repoDir, outDir string, indent bool) (err error) {
-	defer derrors.Wrap(&err, "Generate(%q)", repoDir)
+func Generate(ctx context.Context, repo *git.Repository, outDir string, indent bool) (err error) {
+	defer derrors.Wrap(&err, "Generate()")
 
-	repo, err := gitrepo.Open(ctx, repoDir)
-	if err != nil {
-		return err
-	}
 	new, err := New(ctx, repo)
 	if err != nil {
 		return err
 	}
-	if err = new.Write(outDir, false); err != nil {
+	if err = new.Write(outDir, indent); err != nil {
 		return err
 	}
 
diff --git a/internal/database/generate_test.go b/internal/database/generate_test.go
index ed62cab3..3d92bad1 100644
--- a/internal/database/generate_test.go
+++ b/internal/database/generate_test.go
@@ -14,12 +14,22 @@ import (
 )
 
 func TestGenerate(t *testing.T) {
-	// TODO(https://github.com/golang/go#56417): Write unit tests for Generate.
+	ctx := context.Background()
+	testRepo, err := gitrepo.ReadTxtarRepo(testRepoDir, jan2002)
+	if err != nil {
+		t.Fatal(err)
+	}
+	tmpDir := t.TempDir()
+	err = Generate(ctx, testRepo, tmpDir, true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = cmpDirHashes(tmpDir, validDir); err != nil {
+		t.Error(err)
+	}
 }
 
 func TestGenerateIntegration(t *testing.T) {
-	// Generate (in its current state) can only be tested with respect to the
-	// real contents of vulndb.
 	if !*integration {
 		t.Skip("Skipping integration tests, use flag -integration to run")
 	}
@@ -28,16 +38,17 @@ func TestGenerateIntegration(t *testing.T) {
 
 	ctx := context.Background()
 
-	genDir := t.TempDir()
-	err := Generate(ctx, ".", genDir, false)
+	repo, err := gitrepo.Open(ctx, ".")
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	repo, err := gitrepo.Open(ctx, ".")
+	genDir := t.TempDir()
+	err = Generate(ctx, repo, genDir, false)
 	if err != nil {
 		t.Fatal(err)
 	}
+
 	new, err := New(ctx, repo)
 	if err != nil {
 		t.Fatal(err)