fix: formatUSD helper (#921)

src/utils/format.ts

@@ -291,6 +291,6 @@ export function humanReadableNumber(num: number, decimals = 0): string {
  * @note USD only has 2 decimal places of precision, so this will round to the nearest cent.
  */
 export function formatUSD(value: BigNumberish): string {
-  const formattedString = formatUnits(value, 18);
-  return numeral(formattedString).format("0,0.00");
+  const formattedString = ethers.utils.formatUnits(value, 18);
+  return numeral(Number(formattedString).toFixed(2)).format("0,0.00");
 }

src/utils/tests/format.test.ts

@@ -1,9 +1,12 @@
+import { utils } from "ethers";
+
 import {
   isValidString,
   shortenAddress,
   shortenString,
   shortenTransactionHash,
   smallNumberFormatter,
+  formatUSD,
 } from "../format";
 const VALID_ADDRESS = "0x04Fa0d235C4abf4BcF4787aF4CF447DE572eF828";
 const TX_HASH =
@@ -55,3 +58,17 @@ describe("#smallNumberFormatter", () => {
     expect(smallNumberFormatter(0.01235)).toEqual("0.0124");
   });
 });
+
+describe("#formatUSD", () => {
+  it("should format a wei BigNumber to 2 decimal places", () => {
+    expect(formatUSD(utils.parseEther("1.1"))).toEqual("1.10");
+  });
+
+  it("should format a very small wei number to 2 decimal places", () => {
+    expect(formatUSD(1)).toEqual("0.00");
+  });
+
+  it("should format a large wei BigNumber to 2 decimal places", () => {
+    expect(formatUSD(utils.parseEther("100000.123456"))).toEqual("100,000.12");
+  });
+});