diff --git a/ledger/delta_test.go b/ledger/delta_test.go
new file mode 100644
index 0000000..5804c0d
--- /dev/null
+++ b/ledger/delta_test.go
@@ -0,0 +1,56 @@
+package ledger
+
+import (
+	"testing"
+	"time"
+
+	"github.com/howeyc/ledger"
+	"github.com/howeyc/ledger/decimal"
+)
+
+func TestDelta(t *testing.T) {
+	d, err := time.Parse("2006-01-02", "2099-08-07")
+	if err != nil {
+		t.Fatal(err)
+	}
+	delta := newDelta(d, ledger.Account{
+		Name:    "name",
+		Balance: decimal.NewFromFloat(34.56),
+		Comment: "comment",
+	})
+
+	if delta.Date != d {
+		t.Error(delta.Date)
+	}
+	if delta.Account != "name" {
+		t.Error(delta.Account)
+	}
+	if delta.Value != 34.56 {
+		t.Error(delta.Value)
+	}
+	if delta.Currency != USD {
+		t.Error(delta.Currency)
+	}
+	t.Log(delta)
+
+	d2, _ := time.Parse("2006-01-02", "2099-09-08")
+	delta2 := newDelta(d2, ledger.Account{
+		Name:    "name",
+		Balance: decimal.NewFromFloat(11.11),
+		Comment: "comment",
+	})
+
+	combined := delta.Plus(delta2)
+	if combined.Date != d2 {
+		t.Error(combined.Date)
+	}
+	if combined.Account != "name" {
+		t.Error(combined.Account)
+	}
+	if combined.Value != 45.67 {
+		t.Error(combined.Value)
+	}
+	if combined.Currency != USD {
+		t.Error(combined.Currency)
+	}
+}