feat: add Pest helper functions for testing

This commit introduces helper functions for running tests in Pest,
including `afterEach`, `beforeEach`, `test`, and `it`.

.intellipest/_pest-helper.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace {
+
+    /**
+     * Runs the given closure after each test in the current file.
+     *
+     * @param-closure-this \Tests\TestCase  $closure
+     */
+    function afterEach(?Closure $closure = null): \Pest\PendingCalls\AfterEachCall {}
+
+    /**
+     * Runs the given closure before each test in the current file.
+     *
+     * @param-closure-this \Tests\TestCase  $closure
+     */
+    function beforeEach(?Closure $closure = null): \Pest\PendingCalls\BeforeEachCall {}
+
+    /**
+     * Adds the given closure as a test. The first argument
+     * is the test description; the second argument is
+     * a closure that contains the test expectations.
+     *
+     * @param-closure-this \Tests\TestCase  $closure
+     *
+     * @return ($description is string ? TestCall : HigherOrderTapProxy|TestCall)
+     */
+    function test(?string $description = null, ?Closure $closure = null): \Pest\Support\HigherOrderTapProxy|\Pest\PendingCalls\TestCall {}
+
+    /**
+     * Adds the given closure as a test. The first argument
+     * is the test description; the second argument is
+     * a closure that contains the test expectations.
+     *
+     * @param-closure-this \Tests\TestCase  $closure
+     */
+    function it(string $description, ?Closure $closure = null): \Pest\PendingCalls\TestCall {}
+
+}
+
+namespace Pest {
+
+    class Expectation {
+        public function toBeOne(): self {}
+    }
+
+}
+
+namespace Pest\Expectations {
+
+    class OppositeExpectation {
+        public function toBeOne(): self {}
+    }
+
+}