test: add unit tests for selectStablecoins selector

Author: jpuri

app/selectors/featureFlagController/stableTokens/index.test.ts

@@ -0,0 +1,81 @@
+import { CHAIN_IDS } from '@metamask/transaction-controller';
+import { Hex } from '@metamask/utils';
+import { selectStablecoins, STABLE_TOKENS_FLAG } from '.';
+import mockedEngine from '../../../core/__mocks__/MockedEngine';
+import { mockedEmptyFlagsState, mockedUndefinedFlagsState } from '../mocks';
+
+jest.mock('../../../core/Engine', () => ({
+  init: () => mockedEngine.init(),
+}));
+
+const getMockedFeatureFlag = (value: unknown) => ({
+  engine: {
+    backgroundState: {
+      RemoteFeatureFlagController: {
+        remoteFeatureFlags: {
+          [STABLE_TOKENS_FLAG]: value,
+        },
+        cacheTimestamp: 0,
+      },
+    },
+  },
+});
+
+describe('selectStablecoins', () => {
+  it('returns default stablecoins when flag state is undefined', () => {
+    const result = selectStablecoins(mockedUndefinedFlagsState);
+    expect(result[CHAIN_IDS.MAINNET as Hex]).toContain(
+      '0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48',
+    );
+  });
+
+  it('returns default stablecoins when no flags are set', () => {
+    const result = selectStablecoins(mockedEmptyFlagsState);
+    expect(result).toHaveProperty(CHAIN_IDS.MAINNET);
+    expect(result).toHaveProperty(CHAIN_IDS.ARBITRUM);
+    expect(result).toHaveProperty(CHAIN_IDS.LINEA_MAINNET);
+    expect(result).toHaveProperty(CHAIN_IDS.POLYGON);
+  });
+
+  it('returns flag value when set to a valid object', () => {
+    const flagValue = {
+      '0x1': ['0xaaa', '0xbbb'],
+      '0xa4b1': ['0xccc'],
+    };
+    const result = selectStablecoins(getMockedFeatureFlag(flagValue));
+    expect(result).toStrictEqual(flagValue);
+  });
+
+  it('normalizes addresses and chain IDs to lowercase', () => {
+    const result = selectStablecoins(
+      getMockedFeatureFlag({
+        '0xA4B1': ['0xAf88d065e77c8cC2239327C5EDb3A432268e5831'],
+      }),
+    );
+    expect(result).toStrictEqual({
+      '0xa4b1': ['0xaf88d065e77c8cc2239327c5edb3a432268e5831'],
+    });
+  });
+
+  it('skips non-array entries in flag value', () => {
+    const result = selectStablecoins(
+      getMockedFeatureFlag({
+        '0x1': ['0xaaa'],
+        '0xa4b1': 'not-an-array',
+      }),
+    );
+    expect(result).toStrictEqual({ '0x1': ['0xaaa'] });
+  });
+
+  it('returns default stablecoins when flag is an array', () => {
+    const result = selectStablecoins(
+      getMockedFeatureFlag(['not', 'an', 'object']),
+    );
+    expect(result).toHaveProperty(CHAIN_IDS.MAINNET);
+  });
+
+  it('returns default stablecoins when flag is a primitive', () => {
+    const result = selectStablecoins(getMockedFeatureFlag(true));
+    expect(result).toHaveProperty(CHAIN_IDS.MAINNET);
+  });
+});