adds test for token list fetching (#361)

* adds test for token list fetching

* removes outdated testcase

* makes loading of token list more robust

* Disabled @typescript-eslint/no-unused-expressions for test sources
We use chai for testing and the empty check is always a false positive finding.

.eslintrc.js

@@ -13,4 +13,12 @@ module.exports = {
       },
     ],
   },
+  overrides: [
+    {
+      files: ["*.test.ts", "*.test.tsx"],
+      rules: {
+        "@typescript-eslint/no-unused-expressions": "off",
+      },
+    },
+  ],
 };

src/__tests__/balanceCheck.test.ts

@@ -1,4 +1,3 @@
-/* eslint-disable @typescript-eslint/no-unused-expressions */
 import BigNumber from "bignumber.js";
 import { expect } from "chai";
 

src/__tests__/parser.test.ts

@@ -1,4 +1,3 @@
-/* eslint-disable @typescript-eslint/no-unused-expressions */
 import { BigNumber } from "bignumber.js";
 import * as chai from "chai";
 import { expect } from "chai";

src/__tests__/tokenList.test.ts

@@ -1,19 +1,77 @@
 import { expect } from "chai";
+import { ethers } from "ethers";
 
 import { fetchTokenList } from "../hooks/token";
 import { networkInfo } from "../networks";
 
-describe("fetchTokenList()", () => {
+beforeEach(() => {
+  jest.spyOn(window, "fetch").mockImplementation(() => {
+    return Promise.resolve({
+      json: () =>
+        Promise.resolve({
+          tokens: [
+            {
+              name: "Gnosis",
+              address: "0x6810e776880c02933d47db1b9fc05908e5386b96",
+              symbol: "GNO",
+              decimals: 18,
+            },
+            {
+              name: "Dai Stablecoin",
+              address: "0x6b175474e89094c44da98b954eedeac495271d0f",
+              symbol: "DAI",
+              decimals: 18,
+            },
+            {
+              name: "Spam Token",
+              address: "",
+              symbol: "SPAM",
+              decimals: 0,
+            },
+          ],
+        }),
+      status: 200,
+    } as any);
+  });
+});
+
+describe("Mainnet tokenlist", () => {
+  it("Should parse its response correctly", async () => {
+    const resultingTokens = await fetchTokenList(1);
+    const gnoAddress = ethers.utils.getAddress("0x6810e776880c02933d47db1b9fc05908e5386b96");
+
+    expect(resultingTokens).to.have.lengthOf(2);
+    expect(resultingTokens.get(gnoAddress)?.symbol).to.equal("GNO");
+    expect(resultingTokens.get(gnoAddress)?.address.toLowerCase()).eq(gnoAddress.toLowerCase());
+    expect(resultingTokens.get(gnoAddress)?.decimals).to.equal(18);
+  });
+
+  it("Should not crash on errors", async () => {
+    jest.spyOn(window, "fetch").mockImplementation(() => {
+      return Promise.reject("Unexpected error.");
+    });
+
+    const resultingTokens = await fetchTokenList(1);
+    expect(resultingTokens).to.be.empty;
+  });
+
+  it("Should not crash on unsuccessful fetches", async () => {
+    jest.spyOn(window, "fetch").mockImplementation(() => {
+      return Promise.resolve({
+        status: 404,
+        statusText: "Page not found",
+      } as any);
+    });
+
+    const resultingTokens = await fetchTokenList(1);
+    expect(resultingTokens).to.be.empty;
+  });
+});
+
+describe("Fetch should resolve for all networks", () => {
   for (const chainId of networkInfo.keys()) {
     it(`fetches tokens for ${networkInfo.get(chainId)?.name} network`, () => {
       expect(() => fetchTokenList(chainId)).to.not.throw();
     });
   }
 });
-
-describe("useTokenList()", () => {
-  it("Throws on unknown networks", () => {
-    // TODO - not sure how to test this.
-    expect(1).to.equal(1);
-  });
-});

src/hooks/token.ts

@@ -26,7 +26,10 @@ export const fetchTokenList = async (chainId: number): Promise<TokenMap> => {
   switch (chainId) {
     case 1:
       const mainnetTokenURL = "https://tokens.coingecko.com/uniswap/all.json";
-      tokens = (await (await fetch(mainnetTokenURL)).json()).tokens;
+      tokens = await fetch(mainnetTokenURL)
+        .then((response) => response.json())
+        .then((response) => response.tokens)
+        .catch(() => []);
       break;
     case 4:
       // Hardcoded this because the list provided at