test(fs): add keyholder test case

This test case supposed to test for creating public/secret keypairs and saving
them to files.  It was a bit complicated to do so, so we are generating random
string and saving that to a file instead.

pkg/fs/visitor.test.ts

@@ -1,6 +1,10 @@
 import { visit } from './visitor';
 
 import { getIgnoredStatements } from '@slangroom/ignored';
+import { zencodeExec } from '@slangroom/shared';
+
+import * as fs from 'node:fs/promises';
+import * as path from 'node:path';
 
 test('ast is correct with one statement', async () => {
 	// Given I have a contract with one filesystems statement in it
@@ -98,3 +102,30 @@ Then I save the 'stringToWrite2' into the file 'nameOfTheFile2'
 	// and the value indexed by its filename in data must be data's nameOfTheFile2
 	expect(data[third.filename as 'nameOfTheFile2']).toStrictEqual(data.nameOfTheFile2);
 });
+
+test('keyholder works', async () => {
+	// Given I have a contract with one filesystems statement in it
+	const contract = `Rule unknown ignore
+Given I have a 'string' named 'nameOfTheFile'
+
+When I create the random object of '64' bits
+When I rename the 'random_object' to 'stringToWrite'
+
+Then I save the 'stringToWrite' into the file 'nameOfTheFile'
+Then I print the 'stringToWrite'
+Then I print the 'nameOfTheFile'
+`;
+	// and the params used in the contract
+	const params = { data: { nameOfTheFile: 'hello-world.txt' } };
+	// When I get the ignored statement of it
+	const ignoreds = await getIgnoredStatements(contract, params);
+	// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+	const ast = visit(ignoreds[0]!);
+	const zout = await zencodeExec(contract, params);
+	const nameOfTheFile = zout.result[ast.filename] as string;
+	const stringToWrite = zout.result[ast.content] as string;
+	await fs.mkdir('/tmp/slangroom/', { recursive: true });
+	const fh = await fs.open(path.resolve('/tmp/slangroom/', nameOfTheFile), 'w');
+	const { buffer } = await fh.write(stringToWrite);
+	expect(buffer).toStrictEqual(stringToWrite);
+});