Add tests for improved coverage (#3448)

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

test/helpers/txpool.js

@@ -0,0 +1,40 @@
+const { network } = require('hardhat');
+const { promisify } = require('util');
+
+const queue = promisify(setImmediate);
+
+async function countPendingTransactions () {
+  return parseInt(
+    await network.provider.send('eth_getBlockTransactionCountByNumber', ['pending']),
+  );
+}
+
+async function batchInBlock (txs) {
+  try {
+    // disable auto-mining
+    await network.provider.send('evm_setAutomine', [false]);
+    // send all transactions
+    const promises = txs.map(fn => fn());
+    // wait for node to have all pending transactions
+    while (txs.length > await countPendingTransactions()) {
+      await queue();
+    }
+    // mine one block
+    await network.provider.send('evm_mine');
+    // fetch receipts
+    const receipts = await Promise.all(promises);
+    // Sanity check, all tx should be in the same block
+    const minedBlocks = new Set(receipts.map(({ receipt }) => receipt.blockNumber));
+    expect(minedBlocks.size).to.equal(1);
+
+    return receipts;
+  } finally {
+    // enable auto-mining
+    await network.provider.send('evm_setAutomine', [true]);
+  }
+}
+
+module.exports = {
+  countPendingTransactions,
+  batchInBlock,
+};