wip

tests-tia/AffectedSetTest.php

@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+
+use Pest\TestsTia\Support\Sandbox;
+
+/*
+ * Mutating a source file should narrow replay to the tests that depend
+ * on it. Untouched areas of the suite keep cache-hitting.
+ */
+
+test('editing a source file marks only its dependents as affected', function () {
+    tiaScenario(function (Sandbox $sandbox) {
+        $sandbox->pest(['--tia']);
+
+        $sandbox->write('src/Math.php', <<<'PHP'
+<?php
+
+declare(strict_types=1);
+
+namespace App;
+
+final class Math
+{
+    public static function add(int $a, int $b): int
+    {
+        return $a + $b;
+    }
+
+    public static function sub(int $a, int $b): int
+    {
+        return $a - $b;
+    }
+}
+PHP);
+
+        $process = $sandbox->pest(['--tia']);
+
+        expect($process->isSuccessful())->toBeTrue(tiaOutput($process));
+        expect(tiaOutput($process))->toMatch('/2 affected,\s*1 replayed/');
+    });
+});
+
+test('adding a new test file runs the new test + replays the rest', function () {
+    tiaScenario(function (Sandbox $sandbox) {
+        $sandbox->pest(['--tia']);
+
+        $sandbox->write('tests/ExtraTest.php', <<<'PHP'
+<?php
+
+declare(strict_types=1);
+
+test('extra smoke', function () {
+    expect(true)->toBeTrue();
+});
+PHP);
+
+        $process = $sandbox->pest(['--tia']);
+
+        expect($process->isSuccessful())->toBeTrue(tiaOutput($process));
+        expect(tiaOutput($process))->toMatch('/1 affected,\s*3 replayed/');
+    });
+});

tests-tia/FingerprintDriftTest.php

@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+use Pest\TestsTia\Support\Sandbox;
+
+/*
+ * Fingerprint splits into structural vs environmental. Hand-forge each
+ * drift flavour on a valid graph and assert the right branch fires.
+ */
+
+test('structural drift discards the graph entirely', function () {
+    tiaScenario(function (Sandbox $sandbox) {
+        $sandbox->pest(['--tia']);
+
+        $graphPath = $sandbox->path().'/vendor/pestphp/pest/.temp/tia/graph.json';
+        $graph = json_decode((string) file_get_contents($graphPath), true);
+        $graph['fingerprint']['structural']['composer_lock'] = str_repeat('0', 32);
+        file_put_contents($graphPath, json_encode($graph));
+
+        $process = $sandbox->pest(['--tia']);
+
+        expect($process->isSuccessful())->toBeTrue(tiaOutput($process));
+        expect(tiaOutput($process))->toContain('graph structure outdated');
+    });
+});
+
+test('environmental drift keeps edges, drops results', function () {
+    tiaScenario(function (Sandbox $sandbox) {
+        $sandbox->pest(['--tia']);
+
+        $graphPath = $sandbox->path().'/vendor/pestphp/pest/.temp/tia/graph.json';
+        $graph = json_decode((string) file_get_contents($graphPath), true);
+
+        $edgeCountBefore = count($graph['edges']);
+
+        $graph['fingerprint']['environmental']['php_minor'] = '7.4';
+        $graph['fingerprint']['environmental']['extensions'] = str_repeat('0', 32);
+        file_put_contents($graphPath, json_encode($graph));
+
+        $process = $sandbox->pest(['--tia']);
+
+        expect($process->isSuccessful())->toBeTrue(tiaOutput($process));
+        expect(tiaOutput($process))->toContain('env differs from baseline');
+        expect(tiaOutput($process))->toContain('results dropped, edges reused');
+
+        $graphAfter = $sandbox->graph();
+        expect(count($graphAfter['edges']))->toBe($edgeCountBefore);
+        expect($graphAfter['fingerprint']['environmental']['php_minor'])
+            ->not()->toBe('7.4');
+    });
+});

tests-tia/Fixtures/sample-project/composer.json

@@ -0,0 +1,27 @@
+{
+    "name": "pest/tia-sample-project",
+    "type": "project",
+    "description": "Throw-away fixture used by tests-tia to exercise TIA end-to-end.",
+    "require": {
+        "php": "^8.3"
+    },
+    "autoload": {
+        "psr-4": {
+            "App\\": "src/"
+        }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "Tests\\": "tests/"
+        }
+    },
+    "config": {
+        "sort-packages": true,
+        "allow-plugins": {
+            "pestphp/pest-plugin": true,
+            "php-http/discovery": true
+        }
+    },
+    "minimum-stability": "dev",
+    "prefer-stable": true
+}

tests-tia/Fixtures/sample-project/phpunit.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true"
+         cacheDirectory=".phpunit.cache"
+         executionOrder="depends,defects"
+         failOnRisky="false"
+         failOnWarning="false"
+         displayDetailsOnTestsThatTriggerWarnings="true"
+         displayDetailsOnTestsThatTriggerNotices="true">
+    <testsuites>
+        <testsuite name="default">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+    <source>
+        <include>
+            <directory>src</directory>
+        </include>
+    </source>
+</phpunit>

tests-tia/Fixtures/sample-project/src/Greeter.php

@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App;
+
+final class Greeter
+{
+    public static function greet(string $name): string
+    {
+        return sprintf('Hello, %s!', $name);
+    }
+}

tests-tia/Fixtures/sample-project/src/Math.php

@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App;
+
+final class Math
+{
+    public static function add(int $a, int $b): int
+    {
+        return $a + $b;
+    }
+}

tests-tia/Fixtures/sample-project/tests/GreeterTest.php

@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+use App\Greeter;
+
+test('greeter greets', function () {
+    expect(Greeter::greet('Nuno'))->toBe('Hello, Nuno!');
+});

tests-tia/Fixtures/sample-project/tests/MathTest.php

@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+use App\Math;
+
+test('math add', function () {
+    expect(Math::add(2, 3))->toBe(5);
+});
+
+test('math add negative', function () {
+    expect(Math::add(-1, 1))->toBe(0);
+});

tests-tia/Fixtures/sample-project/tests/Pest.php

@@ -0,0 +1,7 @@
+<?php
+
+declare(strict_types=1);
+
+// Intentionally minimal — tests-tia exercises TIA against the simplest
+// possible Pest harness. Anything more and we end up debugging the
+// fixture instead of the feature under test.

tests-tia/RebuildTest.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+use Pest\TestsTia\Support\Sandbox;
+
+/*
+ * `--tia-rebuild` short-circuits whatever graph is on disk and records
+ * from scratch. Used when the user knows the cache is wrong.
+ */
+
+test('--tia-rebuild forces record mode even with a valid graph', function () {
+    tiaScenario(function (Sandbox $sandbox) {
+        $sandbox->pest(['--tia']);
+        expect($sandbox->hasGraph())->toBeTrue();
+
+        $graphBefore = $sandbox->graph();
+
+        $process = $sandbox->pest(['--tia', '--tia-rebuild']);
+
+        expect($process->isSuccessful())->toBeTrue(tiaOutput($process));
+        expect(tiaOutput($process))->toContain('recording dependency graph');
+
+        $graphAfter = $sandbox->graph();
+        expect(array_keys($graphAfter['edges']))
+            ->toEqualCanonicalizing(array_keys($graphBefore['edges']));
+    });
+});

tests-tia/RecordReplayTest.php

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+use Pest\TestsTia\Support\Sandbox;
+
+/*
+ * The canonical cycle:
+ *   1. Cold `--tia` run → record mode → graph written, tests pass.
+ *   2. Subsequent `--tia` runs → replay mode, every test cache-hits.
+ */
+
+test('cold run records the graph', function () {
+    tiaScenario(function (Sandbox $sandbox) {
+        $process = $sandbox->pest(['--tia']);
+
+        expect($process->isSuccessful())->toBeTrue(tiaOutput($process));
+        expect(tiaOutput($process))->toContain('recording dependency graph');
+        expect($sandbox->hasGraph())->toBeTrue();
+
+        $graph = $sandbox->graph();
+        expect($graph)->toHaveKey('edges');
+        expect(array_keys($graph['edges']))->toContain('tests/MathTest.php');
+        expect(array_keys($graph['edges']))->toContain('tests/GreeterTest.php');
+    });
+});
+
+test('warm run replays every test', function () {
+    tiaScenario(function (Sandbox $sandbox) {
+        // Cold pass: records edges AND snapshots results (series mode
+        // runs `snapshotTestResults` in the same `addOutput` pass).
+        $sandbox->pest(['--tia']);
+
+        $process = $sandbox->pest(['--tia']);
+
+        expect($process->isSuccessful())->toBeTrue(tiaOutput($process));
+        // Zero changes → only the `replayed` fragment appears in the
+        // recap; the `affected` fragment is omitted when count is 0.
+        expect(tiaOutput($process))->toMatch('/3 replayed/');
+        expect(tiaOutput($process))->not()->toMatch('/\d+ affected/');
+    });
+});

tests-tia/SourceRevertTest.php

@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+
+use Pest\TestsTia\Support\Sandbox;
+
+/*
+ * Edit a source file, run TIA (tests re-run), revert to the original
+ * bytes, run again — the revert is itself a change vs the previous
+ * snapshot, so the affected tests re-execute rather than replaying the
+ * stale bad-version cache.
+ */
+
+test('reverting a modified file re-triggers its affected tests', function () {
+    tiaScenario(function (Sandbox $sandbox) {
+        $sandbox->pest(['--tia']);
+
+        $original = (string) file_get_contents($sandbox->path().'/src/Math.php');
+
+        $sandbox->write('src/Math.php', <<<'PHP'
+<?php
+
+declare(strict_types=1);
+
+namespace App;
+
+final class Math
+{
+    public static function add(int $a, int $b): int
+    {
+        return 999; // broken
+    }
+}
+PHP);
+
+        $broken = $sandbox->pest(['--tia']);
+        expect($broken->isSuccessful())->toBeFalse();
+
+        $sandbox->write('src/Math.php', $original);
+
+        $recovered = $sandbox->pest(['--tia']);
+
+        expect($recovered->isSuccessful())->toBeTrue(tiaOutput($recovered));
+        expect(tiaOutput($recovered))->toMatch('/2 affected,\s*1 replayed/');
+    });
+});

tests-tia/StatusReplayTest.php

@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+use Pest\TestsTia\Support\Sandbox;
+
+/*
+ * Cached statuses + assertion counts should survive replay.
+ */
+
+test('assertion counts survive replay', function () {
+    tiaScenario(function (Sandbox $sandbox) {
+        $sandbox->pest(['--tia']);
+
+        $process = $sandbox->pest(['--tia']);
+        $output = tiaOutput($process);
+
+        // MathTest has 2 assertions, GreeterTest has 1 → 3 total.
+        // The "Tests: … (N assertions, … replayed)" banner should show 3.
+        expect($output)->toMatch('/\(3 assertions/');
+    });
+});
+
+test('breaking a test replays as a failure on the next run', function () {
+    tiaScenario(function (Sandbox $sandbox) {
+        // Prime.
+        $sandbox->pest(['--tia']);
+
+        // Break the test. Its test file's edge map still points at
+        // `src/Math.php`; editing the test file counts as a change
+        // and the test re-executes.
+        $sandbox->write('tests/MathTest.php', <<<'PHP'
+<?php
+
+declare(strict_types=1);
+
+use App\Math;
+
+test('math add', function () {
+    expect(Math::add(2, 3))->toBe(999); // wrong
+});
+
+test('math add negative', function () {
+    expect(Math::add(-1, 1))->toBe(0);
+});
+PHP);
+
+        $process = $sandbox->pest(['--tia']);
+
+        expect($process->isSuccessful())->toBeFalse();
+        expect(tiaOutput($process))->toContain('math add');
+    });
+});

tests-tia/Support/Sandbox.php

@@ -0,0 +1,440 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\TestsTia\Support;
+
+use RuntimeException;
+use Symfony\Component\Process\Process;
+
+/**
+ * Throw-away sandbox for a TIA end-to-end scenario.
+ *
+ * On first call in a test run, a shared "template" sandbox is created
+ * under the system temp dir and composer-installed against the host
+ * Pest source. Subsequent `::create()` calls clone the template — cheap
+ * (rcopy + git init) vs. running composer install per test.
+ *
+ * Each test owns its own clone; no cross-test state.
+ *
+ * Set `PEST_TIA_KEEP=1` to skip teardown so a failing scenario can be
+ * reproduced manually — the path is emitted to STDERR.
+ *
+ * @internal
+ */
+final class Sandbox
+{
+    private static ?string $templatePath = null;
+
+    private function __construct(private readonly string $path) {}
+
+    /**
+     * Eagerly provision the shared template. Call once from the harness
+     * bootstrap so parallel workers don't race on first `create()`.
+     */
+    public static function warmTemplate(): void
+    {
+        self::ensureTemplate();
+    }
+
+    public static function create(): self
+    {
+        $template = self::ensureTemplate();
+
+        $path = sys_get_temp_dir()
+            .DIRECTORY_SEPARATOR
+            .'pest-tia-sandbox-'
+            .bin2hex(random_bytes(4));
+
+        self::rcopy($template, $path);
+        self::bootstrapGit($path);
+
+        return new self($path);
+    }
+
+    public function path(): string
+    {
+        return $this->path;
+    }
+
+    public function write(string $relative, string $content): void
+    {
+        $absolute = $this->path.DIRECTORY_SEPARATOR.$relative;
+        $dir = dirname($absolute);
+
+        if (! is_dir($dir) && ! @mkdir($dir, 0755, true) && ! is_dir($dir)) {
+            throw new RuntimeException("Cannot create {$dir}");
+        }
+
+        if (@file_put_contents($absolute, $content) === false) {
+            throw new RuntimeException("Cannot write {$absolute}");
+        }
+    }
+
+    public function delete(string $relative): void
+    {
+        $absolute = $this->path.DIRECTORY_SEPARATOR.$relative;
+
+        if (is_file($absolute)) {
+            @unlink($absolute);
+        }
+    }
+
+    /**
+     * @param  array<int, string>  $flags
+     */
+    public function pest(array $flags = []): Process
+    {
+        // Invoke Pest's bin script through PHP directly rather than the
+        // `vendor/bin/pest` symlink — `rcopy()` loses the `+x` bit when
+        // cloning the template. Going through `php` bypasses the exec
+        // check. Use `PHP_BINARY` (not a bare `php`) so the sandbox
+        // executes under the same interpreter that launched the outer
+        // test suite — otherwise macOS multi-version setups (Herd, brew,
+        // asdf, …) fall back to the first `php` on `$PATH`, which often
+        // lacks the coverage driver TIA's record mode needs.
+        $process = new Process(
+            [PHP_BINARY, 'vendor/pestphp/pest/bin/pest', ...$flags],
+            $this->path,
+            [
+                // Strip any CI signal so TIA doesn't suppress instructions.
+                'GITHUB_ACTIONS' => '',
+                'GITLAB_CI' => '',
+                'CIRCLECI' => '',
+            ],
+        );
+        $process->setTimeout(120.0);
+        $process->run();
+
+        return $process;
+    }
+
+    /**
+     * @return array<string, mixed>|null
+     */
+    public function graph(): ?array
+    {
+        $path = $this->path.'/vendor/pestphp/pest/.temp/tia/graph.json';
+
+        if (! is_file($path)) {
+            return null;
+        }
+
+        $raw = @file_get_contents($path);
+
+        if ($raw === false) {
+            return null;
+        }
+
+        $decoded = json_decode($raw, true);
+
+        return is_array($decoded) ? $decoded : null;
+    }
+
+    public function hasGraph(): bool
+    {
+        return $this->graph() !== null;
+    }
+
+    /**
+     * @param  array<int, string>  $args
+     */
+    public function git(array $args): Process
+    {
+        $process = new Process(['git', ...$args], $this->path);
+        $process->setTimeout(30.0);
+        $process->run();
+
+        return $process;
+    }
+
+    public function destroy(): void
+    {
+        if (getenv('PEST_TIA_KEEP') === '1') {
+            fwrite(STDERR, "[PEST_TIA_KEEP] sandbox: {$this->path}\n");
+
+            return;
+        }
+
+        if (is_dir($this->path)) {
+            self::rrmdir($this->path);
+        }
+    }
+
+    /**
+     * Lazily provisions a once-per-process template with composer already
+     * installed against the host Pest source. Every sandbox clone copies
+     * from here, avoiding a ~30s composer install per test.
+     */
+    private static function ensureTemplate(): string
+    {
+        if (self::$templatePath !== null && is_dir(self::$templatePath.'/vendor')) {
+            return self::$templatePath;
+        }
+
+        // Cache key includes a fingerprint of the host Pest source tree —
+        // when we edit Pest internals, the key changes, old templates
+        // become orphaned, the new template rebuilds. Without this, a
+        // stale template with yesterday's Pest code silently masks today's
+        // code under test.
+        $template = sys_get_temp_dir()
+            .DIRECTORY_SEPARATOR
+            .'pest-tia-template-'
+            .self::hostFingerprint();
+
+        // Serialise template creation across parallel paratest workers.
+        // Without the lock, three workers hitting `ensureTemplate()`
+        // simultaneously each see "no vendor yet → rebuild", stomp on
+        // each other's composer install, and produce half-written
+        // fixtures. `flock` on a sibling lockfile keeps it to one
+        // builder; the others block, then observe the finished
+        // template and skip straight to the fast path.
+        $lockPath = sys_get_temp_dir().DIRECTORY_SEPARATOR.'pest-tia-template.lock';
+        $lock = fopen($lockPath, 'c');
+
+        if ($lock === false) {
+            throw new RuntimeException('Cannot open template lock at '.$lockPath);
+        }
+
+        flock($lock, LOCK_EX);
+
+        try {
+            // Re-check after acquiring the lock — another worker may have
+            // just finished the build while we were waiting.
+            if (is_dir($template.'/vendor')) {
+                self::$templatePath = $template;
+
+                return $template;
+            }
+
+            // Garbage-collect every older template keyed by a different
+            // fingerprint so /tmp doesn't accumulate a 200 MB graveyard
+            // over a month of edits.
+            foreach (glob(sys_get_temp_dir().DIRECTORY_SEPARATOR.'pest-tia-template-*') ?: [] as $orphan) {
+                if ($orphan !== $template) {
+                    self::rrmdir($orphan);
+                }
+            }
+
+            if (is_dir($template)) {
+                self::rrmdir($template);
+            }
+
+            $fixture = __DIR__.'/../Fixtures/sample-project';
+
+            if (! is_dir($fixture)) {
+                throw new RuntimeException('Missing fixture at '.$fixture);
+            }
+
+            if (! @mkdir($template, 0755, true) && ! is_dir($template)) {
+                throw new RuntimeException('Cannot create template at '.$template);
+            }
+
+            self::rcopy($fixture, $template);
+            self::wireHostPest($template);
+            self::composerInstall($template);
+
+            self::$templatePath = $template;
+
+            return $template;
+        } finally {
+            flock($lock, LOCK_UN);
+            fclose($lock);
+        }
+    }
+
+    private static function wireHostPest(string $path): void
+    {
+        $hostRoot = realpath(__DIR__.'/../..');
+
+        if ($hostRoot === false) {
+            throw new RuntimeException('Cannot resolve host Pest root');
+        }
+
+        $composerJson = $path.'/composer.json';
+        $decoded = json_decode((string) file_get_contents($composerJson), true);
+
+        $decoded['repositories'] = [
+            ['type' => 'path', 'url' => $hostRoot, 'options' => ['symlink' => false]],
+        ];
+        $decoded['require']['pestphp/pest'] = '*@dev';
+
+        file_put_contents(
+            $composerJson,
+            json_encode($decoded, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES)."\n",
+        );
+    }
+
+    private static function composerInstall(string $path): void
+    {
+        // Invoke composer via the *same* PHP binary that's running this
+        // process. On macOS multi-version setups (Herd, brew, asdf, etc.)
+        // the `composer` shebang often points at the system PHP, which
+        // may not match the version the test suite booted with — leading
+        // to "your PHP version does not satisfy the requirement" errors
+        // even when the interpreter in use would satisfy it. Going
+        // through `PHP_BINARY` + the located composer binary/phar
+        // sidesteps that entirely.
+        $composer = self::locateComposer();
+        $args = $composer === null
+            ? ['composer', 'install']
+            : [PHP_BINARY, $composer, 'install'];
+
+        $process = new Process(
+            [...$args, '--no-interaction', '--prefer-dist', '--no-progress', '--quiet'],
+            $path,
+        );
+        $process->setTimeout(600.0);
+        $process->run();
+
+        if (! $process->isSuccessful()) {
+            throw new RuntimeException(
+                "composer install failed in template:\n".$process->getOutput().$process->getErrorOutput(),
+            );
+        }
+    }
+
+    /**
+     * Resolves the composer binary to a real path PHP can execute. Returns
+     * `null` when composer isn't findable, in which case the caller falls
+     * back to invoking plain `composer` via `$PATH` (and hopes for the
+     * best — usually fine on CI Linux runners).
+     */
+    private static function locateComposer(): ?string
+    {
+        $probe = new Process(['command', '-v', 'composer']);
+        $probe->run();
+
+        $path = trim($probe->getOutput());
+
+        if ($path === '' || ! is_file($path)) {
+            return null;
+        }
+
+        // `composer` may be a shell-script wrapper (Herd does this) —
+        // resolve the actual phar it invokes. Heuristic: parse out the
+        // last `.phar` argument from the wrapper, fall back to the file
+        // itself if no wrapper is detected.
+        $content = @file_get_contents($path);
+
+        if ($content !== false && preg_match('/\S+\.phar/', $content, $m) === 1) {
+            $phar = $m[0];
+
+            if (is_file($phar)) {
+                return $phar;
+            }
+        }
+
+        return $path;
+    }
+
+    private static function bootstrapGit(string $path): void
+    {
+        // Each clone needs its own repo — TIA's SHA / branch / diff logic
+        // all rely on `.git/`. The template has no git dir so clones start
+        // from a clean slate.
+        $run = function (array $args) use ($path): void {
+            $process = new Process(['git', ...$args], $path);
+            $process->setTimeout(30.0);
+            $process->run();
+
+            if (! $process->isSuccessful()) {
+                throw new RuntimeException('git '.implode(' ', $args).' failed: '.$process->getErrorOutput());
+            }
+        };
+
+        // `.git` may have been cloned from the template if we ever add one
+        // there — nuke it just in case so every sandbox starts fresh.
+        if (is_dir($path.'/.git')) {
+            self::rrmdir($path.'/.git');
+        }
+
+        // Keep `vendor/` and composer lock out of the sandbox's git repo
+        // entirely. With ~thousands of files `git add .` takes tens of
+        // seconds; TIA also ignores vendor paths via `shouldIgnore()` so
+        // tracking them buys nothing except slowness.
+        file_put_contents($path.'/.gitignore', "vendor/\ncomposer.lock\n");
+
+        $run(['init', '-q', '-b', 'main']);
+        $run(['config', 'user.email', 'sandbox@pest.test']);
+        $run(['config', 'user.name', 'Pest Sandbox']);
+        $run(['config', 'commit.gpgsign', 'false']);
+        $run(['add', '.']);
+        $run(['commit', '-q', '-m', 'initial']);
+    }
+
+    /**
+     * Short hash derived from the host Pest source that the template is
+     * built against. Hashing the newest mtime across `src/`, `overrides/`,
+     * and `composer.json` is cheap (one stat each) and catches every edit
+     * that could alter TIA behaviour.
+     */
+    private static function hostFingerprint(): string
+    {
+        $hostRoot = realpath(__DIR__.'/../..');
+
+        if ($hostRoot === false) {
+            return 'unknown';
+        }
+
+        $newest = 0;
+
+        foreach ([$hostRoot.'/src', $hostRoot.'/overrides'] as $dir) {
+            if (! is_dir($dir)) {
+                continue;
+            }
+
+            $iter = new \RecursiveIteratorIterator(
+                new \RecursiveDirectoryIterator($dir, \FilesystemIterator::SKIP_DOTS),
+            );
+
+            foreach ($iter as $file) {
+                if ($file->isFile()) {
+                    $newest = max($newest, $file->getMTime());
+                }
+            }
+        }
+
+        if (is_file($hostRoot.'/composer.json')) {
+            $newest = max($newest, (int) filemtime($hostRoot.'/composer.json'));
+        }
+
+        return substr(sha1($hostRoot.'|'.PHP_VERSION.'|'.$newest), 0, 12);
+    }
+
+    private static function rcopy(string $src, string $dest): void
+    {
+        if (! is_dir($dest) && ! @mkdir($dest, 0755, true) && ! is_dir($dest)) {
+            throw new RuntimeException("Cannot create {$dest}");
+        }
+
+        $iter = new \RecursiveIteratorIterator(
+            new \RecursiveDirectoryIterator($src, \FilesystemIterator::SKIP_DOTS),
+            \RecursiveIteratorIterator::SELF_FIRST,
+        );
+
+        foreach ($iter as $item) {
+            $target = $dest.DIRECTORY_SEPARATOR.$iter->getSubPathname();
+
+            if ($item->isDir()) {
+                @mkdir($target, 0755, true);
+            } else {
+                copy($item->getPathname(), $target);
+            }
+        }
+    }
+
+    private static function rrmdir(string $dir): void
+    {
+        if (! is_dir($dir)) {
+            return;
+        }
+
+        // `rm -rf` shells out but handles symlinks, read-only files, and
+        // the composer-vendor quirks (lock files, .bin symlinks) that
+        // PHP's own recursive delete stumbles on. Non-fatal on failure.
+        $process = new Process(['rm', '-rf', $dir]);
+        $process->setTimeout(60.0);
+        $process->run();
+    }
+}

tests-tia/bootstrap.php

@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * tests-tia bootstrap.
+ *
+ * Pest's automatic `Pest.php` loader scans the configured `testDirectory()`
+ * which defaults to `tests/` and is hard to override from a nested suite.
+ * So instead of relying on `tests-tia/Pest.php` being found, wire the
+ * helpers in via PHPUnit's explicit `bootstrap=` attribute — simpler,
+ * no config-search surprises.
+ */
+require __DIR__.'/../vendor/autoload.php';
+require __DIR__.'/Support/Sandbox.php';
+
+use Pest\TestsTia\Support\Sandbox;
+use Symfony\Component\Process\Process;
+
+// tests-tia exercises the record path end-to-end, which means the
+// sandbox PHP must expose a coverage driver (pcov or xdebug with
+// coverage mode). Without one, `--tia` records zero edges and every
+// scenario assertion fails with a useless "no coverage driver" banner.
+// Bail out loudly at bootstrap so the failure mode is obvious.
+if (! extension_loaded('pcov') && ! extension_loaded('xdebug')) {
+    fwrite(STDERR, "\n");
+    fwrite(STDERR, "  \e[30;43m SKIP \e[0m tests-tia requires a coverage driver (pcov or xdebug).\n");
+    fwrite(STDERR, "         Install one, then retry:  composer test:tia\n\n");
+
+    // Exit 0 so CI doesn't fail when the driver is genuinely absent —
+    // the CI workflow adds pcov explicitly so this branch only fires on
+    // dev machines that haven't set one up.
+    exit(0);
+}
+
+// Pre-warm the shared composer template once, up-front. Without this,
+// parallel workers race on first use — whoever hits `ensureTemplate()`
+// second gets a half-written template. A file-based lock + single
+// bootstrap pre-warm sidesteps the problem entirely.
+Sandbox::warmTemplate();
+
+/**
+ * Runs `$body` inside a fresh sandbox, guaranteeing teardown even when the
+ * body throws. Keeps scenario tests tidy — one line per setup + destroy.
+ */
+function tiaScenario(Closure $body): void
+{
+    $sandbox = Sandbox::create();
+
+    try {
+        $body($sandbox);
+    } finally {
+        $sandbox->destroy();
+    }
+}
+
+/**
+ * Strip ANSI escapes so assertions are terminal-agnostic.
+ */
+function tiaOutput(Process $process): string
+{
+    $output = $process->getOutput().$process->getErrorOutput();
+
+    return preg_replace('/\e\[[0-9;]*m/', '', $output) ?? $output;
+}

tests-tia/phpunit.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="../vendor/phpunit/phpunit/phpunit.xsd"
+         bootstrap="bootstrap.php"
+         colors="true"
+         cacheDirectory="../.phpunit.cache/tests-tia"
+         executionOrder="default"
+         failOnRisky="false"
+         failOnWarning="false">
+    <testsuites>
+        <testsuite name="tia">
+            <directory>.</directory>
+            <exclude>Fixtures</exclude>
+            <exclude>Support</exclude>
+        </testsuite>
+    </testsuites>
+</phpunit>