dev-mcps/dev-server-mcp/test/instance-workspace.test.js

import test from "node:test";
import assert from "node:assert/strict";
import fs from "node:fs";
import os from "node:os";
import path from "node:path";
import {
  assertInstanceKey,
  prepareInstanceWorkspace,
  recordInstall,
  removeInstanceWorkspace
} from "../src/instance-workspace.js";

function roots() {
  const base = fs.mkdtempSync(path.join(os.tmpdir(), "dev-server-copy-"));
  const workspace = path.join(base, "workspace");
  const instances = path.join(base, "instances");
  fs.mkdirSync(workspace);
  fs.mkdirSync(instances);
  return { base, workspace, instances, cleanup: () => fs.rmSync(base, { recursive: true, force: true }) };
}

function execution(workspace, key, files) {
  const directory = path.join(workspace, key);
  fs.mkdirSync(directory, { recursive: true });
  for (const [name, content] of Object.entries(files)) {
    const file = path.join(directory, name);
    fs.mkdirSync(path.dirname(file), { recursive: true });
    fs.writeFileSync(file, content);
  }
  return directory;
}

test("an execution key must be one safe path segment", () => {
  for (const bad of ["../escape", "a/b", "", ".", "with space", "x".repeat(65)]) {
    assert.throws(() => assertInstanceKey(bad), /Invalid execution key/, `accepted ${JSON.stringify(bad)}`);
  }
  assert.equal(assertInstanceKey("7f3c1e2a-b4d5"), "7f3c1e2a-b4d5");
});

test("the copy holds the execution's own files and nothing above them", () => {
  const item = roots();
  try {
    execution(item.workspace, "exec-a", { "package.json": "{}", "src/main.js": "console.log(1)" });
    execution(item.workspace, "exec-b", { "secret.txt": "b's work" });

    const prepared = prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" });

    assert.equal(fs.readFileSync(path.join(prepared.target, "src/main.js"), "utf8"), "console.log(1)");
    assert.ok(!fs.existsSync(path.join(prepared.target, "secret.txt")));
    assert.equal(prepared.entries, 3);
  } finally { item.cleanup(); }
});

test("a symlink into another execution is dropped, not followed", () => {
  // The tree is written by the coding agent, so this is the move that would turn the copy - whose
  // whole purpose is isolation - into a window onto somebody else's work.
  const item = roots();
  try {
    execution(item.workspace, "exec-b", { "secret.txt": "b's work" });
    const source = execution(item.workspace, "exec-a", { "package.json": "{}" });
    fs.symlinkSync(path.join(item.workspace, "exec-b"), path.join(source, "peek"));

    const prepared = prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" });

    assert.ok(!fs.existsSync(path.join(prepared.target, "peek")));
    assert.ok(!fs.existsSync(path.join(prepared.target, "peek", "secret.txt")));
  } finally { item.cleanup(); }
});

test("an execution directory replaced by a symlink is refused outright", () => {
  const item = roots();
  try {
    const outside = path.join(item.base, "outside");
    fs.mkdirSync(outside);
    fs.writeFileSync(path.join(outside, "elsewhere.txt"), "not yours");
    fs.symlinkSync(outside, path.join(item.workspace, "exec-a"));

    assert.throws(
      () => prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" }),
      /escapes the workspace root/
    );
  } finally { item.cleanup(); }
});

test("node_modules is not copied, because the install recreates it", () => {
  const item = roots();
  try {
    execution(item.workspace, "exec-a", { "package.json": "{}", "node_modules/left-pad/index.js": "module.exports=1" });

    const prepared = prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" });

    assert.ok(!fs.existsSync(path.join(prepared.target, "node_modules")));
  } finally { item.cleanup(); }
});

test("a refresh replaces project files and keeps the installed dependencies", () => {
  const item = roots();
  try {
    const source = execution(item.workspace, "exec-a", { "package.json": "{}", "package-lock.json": "{\"v\":1}", "old.js": "gone soon" });
    const first = prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" });
    fs.mkdirSync(path.join(first.target, "node_modules"), { recursive: true });
    fs.writeFileSync(path.join(first.target, "node_modules", "marker"), "installed");
    recordInstall(first.target);

    fs.rmSync(path.join(source, "old.js"));
    fs.writeFileSync(path.join(source, "new.js"), "fresh");
    const second = prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" });

    assert.ok(!fs.existsSync(path.join(second.target, "old.js")), "a deleted file must not survive the refresh");
    assert.equal(fs.readFileSync(path.join(second.target, "new.js"), "utf8"), "fresh");
    assert.equal(fs.readFileSync(path.join(second.target, "node_modules", "marker"), "utf8"), "installed");
    assert.equal(second.installIsCurrent, true);
  } finally { item.cleanup(); }
});

test("a changed lockfile makes the recorded install stale", () => {
  const item = roots();
  try {
    const source = execution(item.workspace, "exec-a", { "package-lock.json": "{\"v\":1}" });
    const first = prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" });
    fs.mkdirSync(path.join(first.target, "node_modules"), { recursive: true });
    recordInstall(first.target);

    fs.writeFileSync(path.join(source, "package-lock.json"), "{\"v\":2}");
    const second = prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" });

    assert.equal(second.installIsCurrent, false);
  } finally { item.cleanup(); }
});

test("with no lockfile the install is never called current", () => {
  const item = roots();
  try {
    execution(item.workspace, "exec-a", { "package.json": "{}" });
    const prepared = prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" });
    fs.mkdirSync(path.join(prepared.target, "node_modules"), { recursive: true });
    recordInstall(prepared.target);

    const again = prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" });
    assert.equal(again.installIsCurrent, false);
  } finally { item.cleanup(); }
});

test("a tree beyond the declared limits is refused instead of filling the volume", () => {
  const item = roots();
  try {
    execution(item.workspace, "exec-a", { "a.txt": "x".repeat(1024), "b.txt": "y".repeat(1024) });
    assert.throws(
      () => prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a", limits: { maxBytes: 1500, maxEntries: 100 } }),
      /exceeds 1500 bytes/
    );
    assert.throws(
      () => prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a", limits: { maxBytes: 1e9, maxEntries: 1 } }),
      /exceeds 1 entries/
    );
  } finally { item.cleanup(); }
});

test("discarding an execution reclaims its directory", () => {
  const item = roots();
  try {
    execution(item.workspace, "exec-a", { "package.json": "{}" });
    const prepared = prepareInstanceWorkspace({ workspaceRoot: item.workspace, instancesRoot: item.instances, key: "exec-a" });
    assert.ok(fs.existsSync(prepared.target));

    removeInstanceWorkspace(item.instances, "exec-a");

    assert.ok(!fs.existsSync(prepared.target));
    assert.ok(fs.existsSync(path.join(item.workspace, "exec-a")), "the workspace itself is not ours to delete");
  } finally { item.cleanup(); }
});