staking inflation rewards test

Author: ipapandinas

tests/staking/inflation.test.ts

@@ -0,0 +1,51 @@
+import { expect } from 'vitest'
+import { u16 } from '@polkadot/types'
+import { given } from '../../helpers'
+
+given('astar')('Reward payouts based on inflation (decayed)', async ({ networks: { astar } }) => {
+  const advanceNextEra = async () => {
+    const state = await astar.api.query.dappStaking.activeProtocolState<any>()
+    await astar.dev.newBlock({ count: 1, unsafeBlockHeight: state.nextEraStart.toNumber() })
+  }
+
+  const palletVersion = (await astar.api.query.inflation.palletVersion<u16>()).toNumber()
+  const config = (await astar.api.query.inflation.activeInflationConfig()).toJSON() as Record<string, any>
+
+  // Scenario 1: baseline, no decay
+  // new parameter on version 2
+  if (palletVersion >= 2) {
+    config.decayRate = 1_000_000_000_000_000_000n; // 100%
+    config.decayFactor = 1_000_000_000_000_000_000n; // 100%
+  }
+
+  await astar.dev.setStorage({
+    balances: {
+      totalIssuance: 8_400_000_000_000_000_000_000_000_000n, // 8.4B
+    },
+    inflation: {
+      activeInflationConfig: config,
+    }
+  });
+
+  await advanceNextEra()
+
+  const issuance_1 = (await astar.api.query.balances.totalIssuance()).toBigInt()
+  expect(issuance_1).toBeGreaterThan(8_400_000_000_000_000_000_000_000_000n)
+
+  // Scenario 2: decayRate = 0%, expect no rewards
+  if (palletVersion >= 2) {
+    config.decayRate = 0n
+    await astar.dev.setStorage({
+      inflation: { activeInflationConfig: config },
+    })
+
+    await advanceNextEra()
+
+    const activeConfig = (await astar.api.query.inflation.activeInflationConfig()).toJSON() as Record<string, any>
+    const decay_factor = activeConfig.decayFactor
+    expect(BigInt(decay_factor)).toBe(0n)
+
+    const issuance_2 = (await astar.api.query.balances.totalIssuance()).toBigInt()
+    expect(issuance_2).toBe(issuance_1) // no increase
+  }
+})