Update docs

test/helpers/customError.js

@@ -0,0 +1,43 @@
+const { expect } = require('chai');
+
+/** Revert handler that supports custom errors. */
+async function expectRevertCustomError(promise, expectedErrorName, args) {
+  if (!Array.isArray(args)) {
+    expect.fail('Expected 3rd array parameter for error arguments');
+  }
+
+  await promise.then(
+    () => expect.fail("Expected promise to throw but it didn't"),
+    ({ message }) => {
+      // The revert message for custom errors looks like:
+      // VM Exception while processing transaction:
+      // reverted with custom error 'InvalidAccountNonce("0x70997970C51812dc3A010C7d01b50e0d17dc79C8", 0)'
+
+      // Attempt to parse as a custom error
+      const match = message.match(/custom error '(?<name>\w+)\((?<args>.*)\)'/);
+      if (!match) {
+        expect.fail(`Could not parse as custom error. ${message}`);
+      }
+      // Extract the error name and parameters
+      const errorName = match.groups.name;
+      const argMatches = [...match.groups.args.matchAll(/-?\w+/g)];
+
+      // Assert error name
+      expect(errorName).to.be.equal(
+        expectedErrorName,
+        `Unexpected custom error name (with found args: [${argMatches.map(([a]) => a)}])`,
+      );
+
+      // Coerce to string for comparison since `arg` can be either a number or hex.
+      const sanitizedExpected = args.map(arg => arg.toString().toLowerCase());
+      const sanitizedActual = argMatches.map(([arg]) => arg.toString().toLowerCase());
+
+      // Assert argument equality
+      expect(sanitizedActual).to.have.members(sanitizedExpected, `Unexpected ${errorName} arguments`);
+    },
+  );
+}
+
+module.exports = {
+  expectRevertCustomError,
+};