diff --git a/src/test/main_test.ts b/src/test/main_test.ts
index f2c70c6..e107b23 100644
--- a/src/test/main_test.ts
+++ b/src/test/main_test.ts
@@ -6,8 +6,6 @@ import path from 'node:path';
 import {spawnSync} from 'node:child_process';
 
 const isWindows = os.platform() === 'win32';
-const fixturesDir = path.join(import.meta.dirname, '../../test/fixtures');
-const distDir = path.join(import.meta.dirname, '../../dist');
 
 const variants = [
   {name: 'async', x, isAsync: true},
@@ -368,79 +366,44 @@ if (!isWindows) {
     });
 
     test('resolves when grandchild holds piped stdout open', async () => {
-      const dir = fs.mkdtempSync(
-        path.join(os.tmpdir(), 'tinyexec-grandchild-')
-      );
-      const runnerScript = path.join(dir, 'runner.mjs');
-      const distPath = JSON.stringify(path.join(distDir, 'main.mjs'));
-      const fixturePath = JSON.stringify(
-        path.join(fixturesDir, 'grandchild.mjs')
-      );
-
-      fs.writeFileSync(
-        runnerScript,
-        `import { x } from ${distPath}
-  const result = await x('node', [${fixturePath}])
-  process.stdout.write(JSON.stringify({ stdout: result.stdout, exitCode: result.exitCode }))
-  `
-      );
-
-      try {
-        const proc = spawnSync('node', [runnerScript], {
-          timeout: 10000,
+      const proc = spawnSync(
+        'node',
+        ['test/fixtures/spawn_grandchild.mjs', 'grandchild.mjs'],
+        {
+          timeout: 3_000,
           encoding: 'utf8',
           killSignal: 'SIGKILL',
           stdio: ['pipe', 'pipe', 'pipe']
-        });
+        }
+      );
 
-        expect(proc.signal).not.toBe('SIGKILL');
-        expect(proc.status).toBe(0);
-        const parsed = JSON.parse(proc.stdout.trim());
-        expect(parsed.exitCode).toBe(0);
-        expect(parsed.stdout).toBe('output\n');
-      } finally {
-        spawnSync('pkill', ['-f', 'tinyexec-test-grandchild']);
-        fs.rmSync(dir, {recursive: true, force: true});
-      }
+      expect(proc.signal).not.toBe('SIGKILL');
+      expect(proc.status).toBe(0);
+      const parsed = JSON.parse(proc.stdout.trim());
+      expect(parsed.exitCode).toBe(0);
+      expect(parsed.stdout).toBe('line1\nline2\n');
+
+      spawnSync('pkill', ['-f', 'grandchild.mjs']);
     });
 
     test('iterator completes when grandchild holds piped stdout open', async () => {
-      const dir = fs.mkdtempSync(
-        path.join(os.tmpdir(), 'tinyexec-grandchild-')
-      );
-      const runnerScript = path.join(dir, 'runner.mjs');
-      const distPath = JSON.stringify(path.join(distDir, 'main.mjs'));
-      const fixturePath = JSON.stringify(
-        path.join(fixturesDir, 'grandchild_multiline.mjs')
-      );
-
-      fs.writeFileSync(
-        runnerScript,
-        `import { x } from ${distPath}
-  const lines = []
-  for await (const line of x('node', [${fixturePath}])) {
-    lines.push(line)
-  }
-  process.stdout.write(JSON.stringify(lines))
-  `
-      );
-
-      try {
-        const proc = spawnSync('node', [runnerScript], {
-          timeout: 10000,
+      const proc = spawnSync(
+        'node',
+        ['test/fixtures/spawn_grandchild_iterator.mjs'],
+        {
+          timeout: 3_000,
           encoding: 'utf8',
           killSignal: 'SIGKILL',
           stdio: ['pipe', 'pipe', 'pipe']
-        });
+        }
+      );
 
-        expect(proc.signal).not.toBe('SIGKILL');
-        expect(proc.status).toBe(0);
-        const parsed = JSON.parse(proc.stdout.trim());
-        expect(parsed).toEqual(['line1', 'line2']);
-      } finally {
-        spawnSync('pkill', ['-f', 'tinyexec-test-grandchild']);
-        fs.rmSync(dir, {recursive: true, force: true});
-      }
+      expect(proc.signal).not.toBe('SIGKILL');
+      expect(proc.status).toBe(0);
+      const parsed = JSON.parse(proc.stdout.trim());
+      expect(parsed).toEqual(['line1', 'line2']);
+
+      spawnSync('pkill', ['-f', 'grandchild.mjs']);
     });
   });
 
diff --git a/test/fixtures/grandchild.mjs b/test/fixtures/grandchild.mjs
index 52ef8ab..6dcfd67 100644
--- a/test/fixtures/grandchild.mjs
+++ b/test/fixtures/grandchild.mjs
@@ -1,13 +1,9 @@
 import {spawn} from 'node:child_process';
 
-// Spawn a grandchild that inherits the piped stdout fd, simulating
-// tsserver inheriting eslint's piped streams. Short timeout to avoid
-// blocking test teardown.
-spawn(
-  process.argv[0],
-  ['-e', 'setTimeout(() => void 0, 3000)'],
-  {stdio: ['ignore', 1, 'ignore']}
-);
+spawn(process.argv[0], ['-e', 'setTimeout(() => void 0, 10_000)'], {
+  stdio: ['ignore', 1, 'ignore']
+});
 
-console.log('output');
+console.log('line1');
+console.log('line2');
 process.exit(0);
diff --git a/test/fixtures/grandchild_multiline.mjs b/test/fixtures/grandchild_multiline.mjs
deleted file mode 100644
index 253e1e2..0000000
--- a/test/fixtures/grandchild_multiline.mjs
+++ /dev/null
@@ -1,11 +0,0 @@
-import {spawn} from 'node:child_process';
-
-spawn(
-  process.argv[0],
-  ['-e', 'setTimeout(() => void 0, 3000)'],
-  {stdio: ['ignore', 1, 'ignore']}
-);
-
-console.log('line1');
-console.log('line2');
-process.exit(0);
diff --git a/test/fixtures/spawn_grandchild.mjs b/test/fixtures/spawn_grandchild.mjs
new file mode 100644
index 0000000..6c18314
--- /dev/null
+++ b/test/fixtures/spawn_grandchild.mjs
@@ -0,0 +1,10 @@
+import path from 'node:path';
+import {exec} from '../../dist/main.mjs';
+
+const childScript = path.join(import.meta.dirname, 'grandchild.mjs');
+
+const result = await exec('node', [childScript]);
+
+process.stdout.write(
+  JSON.stringify({stdout: result.stdout, exitCode: result.exitCode})
+);
diff --git a/test/fixtures/spawn_grandchild_iterator.mjs b/test/fixtures/spawn_grandchild_iterator.mjs
new file mode 100644
index 0000000..84c9b3d
--- /dev/null
+++ b/test/fixtures/spawn_grandchild_iterator.mjs
@@ -0,0 +1,12 @@
+import path from 'node:path';
+import {exec} from '../../dist/main.mjs';
+
+const childScript = path.join(import.meta.dirname, 'grandchild.mjs');
+
+const lines = [];
+
+for await (const line of exec('node', [childScript])) {
+  lines.push(line);
+}
+
+process.stdout.write(JSON.stringify(lines));