Test MASP inverse conversions

.changelog/unreleased/testing/4193-test-inverse-conversions.md

@@ -0,0 +1,2 @@
+- Added tests for MASP inverse conversions.
+  ([\#4193](https://github.com/anoma/namada/pull/4193))

crates/shielded_token/src/masp/shielded_wallet.rs

@@ -1989,6 +1989,131 @@ mod test_shielded_wallet {
         assert!(wallet.compute_shielded_balance(&vk).await.is_err())
     }
 
+    // Test that `compute_exchanged_amount` can perform inverse conversions to
+    // match the desired epoch
+    #[tokio::test]
+    async fn test_inverse_conversions() {
+        let (channel, mut context) = MockNamadaIo::new();
+        // the response to the current masp epoch query
+        channel
+            .send(MaspEpoch::new(5).serialize_to_vec())
+            .expect("Test failed");
+        let temp_dir = tempdir().unwrap();
+        let mut wallet = TestingContext::new(FsShieldedUtils::new(
+            temp_dir.path().to_path_buf(),
+        ));
+        let native_token =
+            TestingContext::<FsShieldedUtils>::query_native_token(
+                context.client(),
+            )
+            .await
+            .expect("Test failed");
+        let native_token_denom =
+            TestingContext::<FsShieldedUtils>::query_denom(
+                context.client(),
+                &native_token,
+            )
+            .await
+            .expect("Test failed");
+
+        for epoch in 0..=5 {
+            wallet.add_asset_type(AssetData {
+                token: native_token.clone(),
+                denom: native_token_denom,
+                position: MaspDigitPos::Zero,
+                epoch: Some(MaspEpoch::new(epoch)),
+            });
+        }
+
+        for epoch in 0..5 {
+            let mut conv = I128Sum::from_pair(
+                AssetData {
+                    token: native_token.clone(),
+                    denom: native_token_denom,
+                    position: MaspDigitPos::Zero,
+                    epoch: Some(MaspEpoch::new(epoch)),
+                }
+                .encode()
+                .unwrap(),
+                -1,
+            );
+            conv += I128Sum::from_pair(
+                AssetData {
+                    token: native_token.clone(),
+                    denom: native_token_denom,
+                    position: MaspDigitPos::Zero,
+                    epoch: Some(MaspEpoch::new(epoch + 1)),
+                }
+                .encode()
+                .unwrap(),
+                2,
+            );
+            context.add_conversions(
+                AssetData {
+                    token: native_token.clone(),
+                    denom: native_token_denom,
+                    position: MaspDigitPos::Zero,
+                    epoch: Some(MaspEpoch::new(epoch)),
+                },
+                (
+                    native_token.clone(),
+                    native_token_denom,
+                    MaspDigitPos::Zero,
+                    MaspEpoch::new(epoch),
+                    conv,
+                    MerklePath::from_path(vec![], 0),
+                ),
+            );
+        }
+
+        let vk = arbitrary_vk();
+        let pa = arbitrary_pa();
+        // Shield at epoch 5
+        let asset_data = AssetData {
+            token: native_token.clone(),
+            denom: native_token_denom,
+            position: MaspDigitPos::Zero,
+            epoch: Some(MaspEpoch::new(5)),
+        };
+        wallet.add_asset_type(asset_data.clone());
+        wallet.add_note(create_note(asset_data.clone(), 10, pa), vk);
+        let balance = wallet
+            .compute_shielded_balance(&vk)
+            .await
+            .unwrap()
+            .unwrap_or_else(ValueSum::zero);
+        // TODO: would be nice to check even earlier epochs but for that we need
+        // to construct conversions properly, just like the protocol does, i.e.
+        // with conversions for non-consecutive epochs
+
+        // Query the balance with conversions at epoch 4
+        let amount = wallet
+            .compute_exchanged_amount(
+                context.client(),
+                context.io(),
+                balance,
+                MaspEpoch::new(4),
+                Conversions::new(),
+            )
+            .await
+            .unwrap()
+            .0;
+        assert_eq!(
+            amount,
+            I128Sum::from_pair(
+                AssetData {
+                    token: native_token.clone(),
+                    denom: native_token_denom,
+                    position: MaspDigitPos::Zero,
+                    epoch: Some(MaspEpoch::new(4)),
+                }
+                .encode()
+                .unwrap(),
+                5
+            )
+        );
+    }
+
     #[tokio::test]
     // Test that the estimated rewards are 0 when no conversions are available
     async fn test_estimate_rewards_no_conversions() {
@@ -2103,7 +2228,7 @@ mod test_shielded_wallet {
         let pa = arbitrary_pa();
         let asset_data = AssetData {
             token: native_token.clone(),
-            denom: 0.into(),
+            denom: native_token_denom,
             position: MaspDigitPos::Zero,
             epoch: Some(MaspEpoch::new(2)),
         };

crates/tests/src/integration/masp.rs

@@ -1688,6 +1688,28 @@ fn masp_incentives() -> Result<()> {
     assert!(captured.result.is_ok());
     assert!(captured.contains("nam: 0.18887"));
 
+    // Assert the rewards estimate are 0 since we haven't shielded any more
+    // tokens
+    let captured = CapturedOutput::of(|| {
+        run(
+            &node,
+            Bin::Client,
+            vec![
+                "estimate-shielding-rewards",
+                "--key",
+                AA_VIEWING_KEY,
+                "--node",
+                validator_one_rpc,
+            ],
+        )
+    });
+    assert!(captured.result.is_ok());
+    assert!(
+        captured.contains(
+            "Estimated native token rewards for the next MASP epoch: 0"
+        )
+    );
+
     // Assert NAM balance at MASP pool is exclusively the
     // rewards from the shielded BTC
     let captured = CapturedOutput::of(|| {