diff --git a/wallet/wallet_test.go b/wallet/wallet_test.go
index 2e26f58..cc66fa6 100644
--- a/wallet/wallet_test.go
+++ b/wallet/wallet_test.go
@@ -12,6 +12,14 @@ func TestWallet(t *testing.T) {
 		}
 	}
 
+	assertError := func(t testing.TB, err error) {
+		t.Helper()
+
+		if err == nil {
+			t.Error("wanted an error but didn't get one")
+		}
+	}
+
 	t.Run("deposit", func(t *testing.T) {
 		wallet := Wallet{}
 		wallet.Deposit(10)
@@ -28,10 +36,8 @@ func TestWallet(t *testing.T) {
 		startingBalance := Bitcoin(20)
 		wallet := Wallet{balance: startingBalance}
 		err := wallet.Withdraw(100)
-		assertBalance(t, wallet, startingBalance)
 
-		if err == nil {
-			t.Error("wanted an error but didn't get one")
-		}
+		assertError(t, err)
+		assertBalance(t, wallet, startingBalance)
 	})
 }