Add pre-flight test run on main branch before spawning agents

Runs test command once on current branch before creating worktrees.
If tests fail on main, warns user but continues. Catches broken test
environments before wasting time on 5 parallel agents.

Generated by thinktank Opus (5 agents, ALL pass, Copeland: #2 at +4).

Closes #64

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: unknown

src/commands/run.test.ts

@@ -10,6 +10,7 @@ import {
   loadLatestResult,
   makeResultFilename,
   mergeRetryResults,
+  preflightTestRun,
   preflightValidation,
 } from "./run.js";
 
@@ -436,3 +437,34 @@ describe("checkDiskSpace", () => {
     }
   });
 });
+
+describe("preflightTestRun", () => {
+  it("returns null when test command succeeds", async () => {
+    const result = await preflightTestRun("node --version", process.cwd());
+    assert.equal(result, null);
+  });
+
+  it("returns warning when test command fails", async () => {
+    const result = await preflightTestRun("node --require ./nonexistent-module.js", process.cwd());
+    assert.ok(result);
+    assert.ok(result.includes("failed on the current branch"));
+    assert.ok(result.includes("test environment may already be broken"));
+  });
+
+  it("returns warning with output snippet when test produces output", async () => {
+    const result = await preflightTestRun("node --require ./nonexistent-module.js", process.cwd());
+    assert.ok(result);
+    assert.ok(result.includes("failed on the current branch"));
+  });
+
+  it("returns null for a passing test with output", async () => {
+    const result = await preflightTestRun("node --version", process.cwd());
+    assert.equal(result, null);
+  });
+
+  it("returns warning when command is not found", async () => {
+    const result = await preflightTestRun("nonexistent-command-xyz", process.cwd());
+    assert.ok(result);
+    assert.ok(result.includes("failed on the current branch"));
+  });
+});

src/commands/run.ts

@@ -1,9 +1,11 @@
+import { execFile } from "node:child_process";
 import { mkdir, readFile, statfs, writeFile } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
+import { promisify } from "node:util";
 import { getDefaultRunner, getRunner } from "../runners/registry.js";
 import { analyzeConvergence, copelandRecommend, recommend } from "../scoring/convergence.js";
-import { runTests, validateTestCommand } from "../scoring/test-runner.js";
+import { parseTestCommand, runTests, validateTestCommand } from "../scoring/test-runner.js";
 import type { AgentResult, EnsembleResult, RunOptions } from "../types.js";
 import { displayApplyInstructions, displayHeader, displayResults } from "../utils/display.js";
 import {
@@ -14,6 +16,8 @@ import {
   removeWorktree,
 } from "../utils/git.js";
 
+const execFileAsync = promisify(execFile);
+
 function formatBytes(bytes: number): string {
   if (bytes >= 1024 * 1024 * 1024) {
     return `${(bytes / (1024 * 1024 * 1024)).toFixed(1)} GB`;
@@ -163,6 +167,15 @@ export async function retry(opts: RunOptions): Promise<void> {
     process.exit(1);
   }
 
+  // Pre-flight test run: catch broken test environments before spawning agents
+  if (opts.testCmd) {
+    const repoRoot = await getRepoRoot();
+    const testWarning = await preflightTestRun(opts.testCmd, repoRoot);
+    if (testWarning) {
+      console.warn(`  ⚠ ${testWarning}`);
+    }
+  }
+
   // Clean up old worktrees
   await cleanupBranches().catch(() => {});
 
@@ -284,6 +297,34 @@ export async function retry(opts: RunOptions): Promise<void> {
   process.removeListener("SIGINT", handleSigint);
 }
 
+/**
+ * Run the test command once on the current branch before spawning agents.
+ * Returns a warning string if the tests fail, or null if they pass.
+ */
+export async function preflightTestRun(testCmd: string, repoRoot: string): Promise<string | null> {
+  const { cmd, args } = parseTestCommand(testCmd);
+  if (!cmd) return null;
+
+  try {
+    await execFileAsync(cmd, args, {
+      cwd: repoRoot,
+      timeout: 60_000,
+      shell: true,
+      env: { ...process.env, CI: "true" },
+    });
+    return null;
+  } catch (err: unknown) {
+    const e = err as { stdout?: string; stderr?: string; code?: number | string };
+    const output = ((e.stdout ?? "") + (e.stderr ?? "")).trim();
+    const snippet = output.length > 200 ? `${output.slice(0, 200)}...` : output;
+    return (
+      `Test command "${testCmd}" failed on the current branch before spawning agents. ` +
+      "Your test environment may already be broken.\n" +
+      (snippet ? `  Output: ${snippet}` : "")
+    );
+  }
+}
+
 export async function run(opts: RunOptions): Promise<void> {
   displayHeader(opts.prompt, opts.attempts, opts.model);
 
@@ -310,6 +351,15 @@ export async function run(opts: RunOptions): Promise<void> {
     process.exit(1);
   }
 
+  // Pre-flight test run: catch broken test environments before spawning agents
+  if (opts.testCmd) {
+    const repoRoot = await getRepoRoot();
+    const testWarning = await preflightTestRun(opts.testCmd, repoRoot);
+    if (testWarning) {
+      console.warn(`  ⚠ ${testWarning}`);
+    }
+  }
+
   // Clean up any leftover worktrees/branches from previous runs
   await cleanupBranches().catch(() => {});