adds test for success case

zebra-consensus/src/transaction/tests.rs

@@ -215,6 +215,57 @@ async fn mempool_request_with_missing_input_is_rejected() {
     );
 }
 
+#[tokio::test]
+async fn mempool_request_with_present_input_is_accepted() {
+    let mut state: MockService<_, _, _, _> = MockService::build().for_prop_tests();
+    let verifier = Verifier::new(Network::Mainnet, state.clone());
+
+    let height = NetworkUpgrade::Canopy
+        .activation_height(Network::Mainnet)
+        .expect("Canopy activation height is specified");
+    let fund_height = (height - 1).expect("fake source fund block height is too small");
+    let (input, output, known_utxos) = mock_transparent_transfer(fund_height, true, 0);
+
+    // Create a non-coinbase V4 tx with the last valid expiry height.
+    let tx = Transaction::V4 {
+        inputs: vec![input],
+        outputs: vec![output],
+        lock_time: LockTime::unlocked(),
+        expiry_height: height,
+        joinsplit_data: None,
+        sapling_shielded_data: None,
+    };
+
+    let input_outpoint = match tx.inputs()[0] {
+        transparent::Input::PrevOut { outpoint, .. } => outpoint,
+        transparent::Input::Coinbase { .. } => panic!("requires a non-coinbase transaction"),
+    };
+
+    tokio::spawn(async move {
+        state
+            .expect_request(zebra_state::Request::UnspentBestChainUtxo(input_outpoint))
+            .await
+            .expect("verifier should call mock state service")
+            .respond(zebra_state::Response::UnspentBestChainUtxo(
+                known_utxos
+                    .get(&input_outpoint)
+                    .map(|utxo| utxo.utxo.clone()),
+            ));
+    });
+
+    let verifier_response = verifier
+        .oneshot(Request::Mempool {
+            transaction: tx.into(),
+            height,
+        })
+        .await;
+
+    assert!(
+        verifier_response.is_ok(),
+        "expected successful verification, got: {verifier_response:?}"
+    );
+}
+
 #[test]
 fn v5_transaction_with_no_outputs_fails_validation() {
     let transaction = fake_v5_transactions_for_network(