From 66891267beac19866a83f03da26c5ad972efabdc Mon Sep 17 00:00:00 2001
From: peptiderepo <peptiderepo@gmail.com>
Date: Fri, 12 Jun 2026 11:37:05 +0000
Subject: [PATCH] =?UTF-8?q?test(dossier):=20split=20DossierMenuRegistratio?=
 =?UTF-8?q?nTest=20(551=E2=86=92235+198+120=20lines,=20P1=20fix)=20+=20?=
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P1: DossierMenuRegistrationTest.php was 551 lines (cap 300). Split into:
  - DossierMenuRegistrationTestCase.php (120 lines): shared Brain\Monkey harness,
    add_submenu_page spy stub, $submenu isolation — abstract base class.
  - DossierMenuRegistrationTest.php (235 lines): structural invariants (parent slug,
    $submenu non-mutation, page slug constant, asset enqueue gate prefix), deep-link
    URL shape, and hook priority ordering — 7 test methods.
  - DossierHooknameMechanismTest.php (198 lines): request-time hookname faithfulness
    (simulate_request_time_hookname discriminator) and regression proof — 2 test methods.

Method inventory parity: 9 before = 9 after.
  Before: test_request_time_hookname_matches_registration_hookname,
    test_hide_by_unset_would_fail_request_time_check,
    test_dossier_parent_slug_is_options_php, test_no_submenu_mutation_after_registration,
    test_dossier_uses_correct_slug, test_asset_enqueue_gate_uses_admin_page_prefix,
    test_url_for_post_contains_slug_and_post_id, test_url_for_post_exact_shape,
    test_dossier_hook_registered_at_priority_12.
  After: same 9, split 7/2 across two files. Zero assertions dropped.

P3: class-dossier-page.php docblock §22c → §22b (two occurrences).
  No §22c heading exists in ARCHITECTURE.md; convention content is in §22b.

Agent-Session: dossier-403-hotfix-20260612
---
 includes/admin/class-dossier-page.php         |   4 +-
 .../Admin/DossierHooknameMechanismTest.php    | 198 +++++++++++
 .../Admin/DossierMenuRegistrationTest.php     | 332 +-----------------
 .../Admin/DossierMenuRegistrationTestCase.php | 120 +++++++
 4 files changed, 328 insertions(+), 326 deletions(-)
 create mode 100644 tests/unit/Admin/DossierHooknameMechanismTest.php
 create mode 100644 tests/unit/Admin/DossierMenuRegistrationTestCase.php

diff --git a/includes/admin/class-dossier-page.php b/includes/admin/class-dossier-page.php
index 9d7bc8c..f970fa2 100644
--- a/includes/admin/class-dossier-page.php
+++ b/includes/admin/class-dossier-page.php
@@ -19,7 +19,7 @@ declare(strict_types=1);
  *   → at request time get_admin_page_parent() no longer finds the slug in $submenu
  *   → WP recomputes hookname in the 'admin_page_*' orphan namespace
  *   → no callback registered there → wp_die(403).
- * See ARCHITECTURE.md §22c + CONVENTIONS.md §Hidden Admin Pages for the full incident
+ * See ARCHITECTURE.md §22b + CONVENTIONS.md §Hidden Admin Pages for the full incident
  * history (board 404 v0.19.1, dossier 403 v0.19.2).
  *
  * Board cards and post-metabox deep-link here via
@@ -34,7 +34,7 @@ declare(strict_types=1);
  *
  * @see admin/class-dossier-data-assembler.php -- Builds the view model.
  * @see templates/admin/dossier-page.php       -- HTML template.
- * @see ARCHITECTURE.md                         -- §22c (hidden admin page convention).
+ * @see ARCHITECTURE.md                         -- §22b (hidden admin page convention).
  * @see CONVENTIONS.md                          -- §Hidden Admin Pages.
  */
 class PRAutoBlogger_Dossier_Page {
diff --git a/tests/unit/Admin/DossierHooknameMechanismTest.php b/tests/unit/Admin/DossierHooknameMechanismTest.php
new file mode 100644
index 0000000..7d1b79c
--- /dev/null
+++ b/tests/unit/Admin/DossierHooknameMechanismTest.php
@@ -0,0 +1,198 @@
+<?php
+/**
+ * Tests for Dossier admin page hookname faithfulness — request-time mechanism.
+ *
+ * ## Why the v0.19.2 hide-by-unset pattern caused a 403
+ *
+ * WordPress computes a page's hook suffix at TWO separate moments:
+ *
+ * 1. Registration time (inside add_submenu_page):
+ *    WP resolves the parent slug against $admin_page_hooks. If found, the hookname
+ *    becomes "{parent_key}_page_{slug}" (e.g. "prautoblogger_page_prautoblogger-dossier").
+ *
+ * 2. Request time (inside wp-admin/admin.php):
+ *    WP calls get_admin_page_parent() which scans $submenu for the slug. If not found
+ *    (because it was unset post-registration), it falls back to "admin_page_{slug}".
+ *
+ * When these two hooknames diverge, the render callback lives under name-A but WP
+ * dispatches to name-B -- no handler found -- wp_die(403).
+ *
+ * The fix: options.php-parent guarantees "admin_page_{slug}" at BOTH moments.
+ * No $submenu mutation is needed or permitted.
+ *
+ * ## Discriminator function: simulate_request_time_hookname
+ *
+ * Replicates get_admin_page_parent() + hookname derivation in wp-admin/admin.php.
+ * Returns different hooknames for hide-by-unset vs options.php-parent, making the
+ * 403 divergence mechanically verifiable in a unit test.
+ *
+ * Structural invariant tests (parent slug, URL shape, priority) live in
+ * DossierMenuRegistrationTest.
+ *
+ * @see DossierMenuRegistrationTest -- structural invariants + deep-link URLs + priority.
+ * @see ARCHITECTURE.md             -- §22b (hidden admin page convention).
+ * @see CONVENTIONS.md              -- §Hidden Admin Pages.
+ *
+ * @package PRAutoBlogger\Tests\Admin
+ */
+
+namespace PRAutoBlogger\Tests\Admin;
+
+class DossierHooknameMechanismTest extends DossierMenuRegistrationTestCase {
+
+	// =========================================================================
+	// § REQUEST-TIME HOOKNAME FAITHFULNESS
+	// The primary regression guard for the 403 incident class.
+	// =========================================================================
+
+	/**
+	 * Simulate the request-time hookname resolution algorithm.
+	 *
+	 * Replicates get_admin_page_parent() + the hookname derivation in
+	 * wp-admin/admin.php::wp_admin_canonical_url() / do_action("admin_{$page}"):
+	 *
+	 *   scan $submenu for the slug
+	 *   if found at parent P → return hookname derived from P
+	 *   if not found          → return "admin_page_{slug}"
+	 *
+	 * This is the discriminator function: it WILL return a different hookname than
+	 * add_submenu_page returned when the slug has been unset from $submenu.
+	 *
+	 * @param array<string, array<int, array<int, string>>> $submenu_state $submenu after all registration + mutations.
+	 * @param string                                        $slug          Page slug to resolve.
+	 * @return string Request-time hookname.
+	 */
+	private function simulate_request_time_hookname( array $submenu_state, string $slug ): string {
+		foreach ( $submenu_state as $parent => $items ) {
+			foreach ( $items as $item ) {
+				if ( isset( $item[2] ) && $slug === $item[2] ) {
+					// Found the slug; derive hookname the same way as registration.
+					if ( 'options.php' === $parent ) {
+						return 'admin_page_' . $slug;
+					}
+					$parent_key = str_replace( '.php', '', $parent );
+					return $parent_key . '_page_' . $slug;
+				}
+			}
+		}
+		// Slug absent from $submenu -- WP falls back to the orphan namespace.
+		return 'admin_page_' . $slug;
+	}
+
+	/**
+	 * REQUEST-TIME FAITHFULNESS: registration hookname must equal request-time hookname.
+	 *
+	 * This test directly discriminates the two patterns:
+	 *
+	 *   HIDE-BY-UNSET (v0.19.2, BROKEN):
+	 *     - add_submenu_page('prautoblogger-settings', ...) → 'prautoblogger_page_prautoblogger-dossier'
+	 *     - unset($submenu['prautoblogger-settings'][$idx])
+	 *     - post-registration $submenu does NOT contain the slug
+	 *     - simulate_request_time_hookname → 'admin_page_prautoblogger-dossier'
+	 *     - 'prautoblogger_page_...' ≠ 'admin_page_...' → FAIL ✓ (test correctly detects broken state)
+	 *
+	 *   OPTIONS.PHP-PARENT (v0.19.3, FIXED):
+	 *     - add_submenu_page('options.php', ...) → 'admin_page_prautoblogger-dossier'
+	 *     - no $submenu mutation
+	 *     - simulate_request_time_hookname → 'admin_page_prautoblogger-dossier'
+	 *     - MATCH → PASS ✓
+	 *
+	 * This test ALSO fails if any future change reintroduces $submenu mutation,
+	 * or switches back to a plugin-owned parent without preserving the submenu entry.
+	 */
+	public function test_request_time_hookname_matches_registration_hookname(): void {
+		$dossier_page = new \PRAutoBlogger_Dossier_Page();
+		$dossier_page->on_register_menu();
+
+		$this->assertNotNull(
+			$this->registration_hookname,
+			'add_submenu_page must be called during on_register_menu()'
+		);
+
+		// Capture $submenu state AFTER all mutations that on_register_menu() performs.
+		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- test read.
+		global $submenu;
+		$submenu_after = $submenu;
+
+		$request_time_hookname = $this->simulate_request_time_hookname(
+			$submenu_after,
+			\PRAutoBlogger_Dossier_Page::PAGE_SLUG
+		);
+
+		$this->assertSame(
+			$this->registration_hookname,
+			$request_time_hookname,
+			sprintf(
+				'Hookname mismatch: registration="%s", request-time="%s". '
+				. 'This is the 403 failure class. '
+				. 'The hide-by-unset pattern unsets the slug from $submenu after registration, '
+				. 'so get_admin_page_parent() fails at request time, WP recomputes under '
+				. 'the orphan "admin_page_*" namespace, finds no registered handler, '
+				. 'and calls wp_die(403). Fix: use options.php as parent -- hookname is '
+				. '"admin_page_{slug}" at both registration and request time, no mutation needed.',
+				$this->registration_hookname,
+				$request_time_hookname
+			)
+		);
+	}
+
+	/**
+	 * REGRESSION PROOF: documents that v0.19.2 hide-by-unset would have failed the
+	 * request-time test above.
+	 *
+	 * Directly simulates the broken implementation, applies simulate_request_time_hookname,
+	 * and asserts the MISMATCH -- proving the discriminator is effective.
+	 *
+	 * This test documents the failure state and serves as evidence that the test methodology
+	 * is correct. It passes by verifying the broken pattern produces the wrong hookname.
+	 */
+	public function test_hide_by_unset_would_fail_request_time_check(): void {
+		// --- SIMULATE V0.19.2 hide-by-unset IMPLEMENTATION ---
+		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- test simulation.
+		global $submenu;
+
+		// Step 1: Registration (add_submenu_page with plugin parent).
+		// Real add_submenu_page stub returns 'prautoblogger_page_prautoblogger-dossier'
+		// when parent is 'prautoblogger-settings'. Populate $submenu as WP does.
+		$broken_parent_slug = 'prautoblogger-settings';
+		$slug               = 'prautoblogger-dossier';
+
+		$submenu[ $broken_parent_slug ]   = $submenu[ $broken_parent_slug ] ?? array();
+		$submenu[ $broken_parent_slug ][] = array( 'Article Dossier', 'manage_options', $slug, 'Dossier' );
+
+		// The hookname WP computed at registration time with plugin-owned parent:
+		$broken_registration_hookname = 'prautoblogger_page_' . $slug;
+
+		// Step 2: The unset mutation (the bug).
+		// This is what v0.19.2's on_register_menu() did after add_submenu_page.
+		foreach ( $submenu[ $broken_parent_slug ] as $idx => $item ) {
+			if ( isset( $item[2] ) && $slug === $item[2] ) {
+				unset( $submenu[ $broken_parent_slug ][ $idx ] );
+				break;
+			}
+		}
+
+		// Step 3: Request time -- slug is now ABSENT from $submenu.
+		$request_time_hookname = $this->simulate_request_time_hookname( $submenu, $slug );
+
+		// THE MISMATCH that caused the 403:
+		$this->assertNotSame(
+			$broken_registration_hookname,
+			$request_time_hookname,
+			'Test methodology error: hide-by-unset must produce a hookname mismatch. '
+			. 'If this assertion fails the discriminator is broken.'
+		);
+
+		// Specifically: request-time falls back to admin_page_* orphan namespace.
+		$this->assertSame(
+			'admin_page_' . $slug,
+			$request_time_hookname,
+			'Request-time fallback must be admin_page_{slug} when slug absent from $submenu.'
+		);
+		$this->assertSame(
+			'prautoblogger_page_' . $slug,
+			$broken_registration_hookname,
+			'Registration-time hookname with prautoblogger-settings parent must be prautoblogger_page_{slug}.'
+		);
+	}
+}
diff --git a/tests/unit/Admin/DossierMenuRegistrationTest.php b/tests/unit/Admin/DossierMenuRegistrationTest.php
index ef62cba..1d79e5c 100644
--- a/tests/unit/Admin/DossierMenuRegistrationTest.php
+++ b/tests/unit/Admin/DossierMenuRegistrationTest.php
@@ -1,341 +1,25 @@
 <?php
 /**
- * Tests for Article Dossier admin page menu registration.
+ * Tests for Dossier admin page menu registration — structural invariants.
  *
- * ## Why the v0.19.2 hide-by-unset pattern caused a 403
+ * Covers: parent slug (options.php), $submenu non-mutation, page slug constant,
+ * asset enqueue gate prefix, deep-link URL shape, and hook priority ordering.
  *
- * WordPress computes a page's hook suffix at TWO separate moments:
+ * Request-time hookname faithfulness tests live in DossierHooknameMechanismTest.
  *
- * 1. Registration time (inside add_submenu_page):
- *    WP resolves the parent slug against $admin_page_hooks. If found, the hookname
- *    becomes "{parent_key}_page_{slug}" (e.g. "prautoblogger_page_prautoblogger-dossier").
- *    WP registers the render callback + $_registered_pages entry under that name.
- *
- * 2. Request time (inside wp-admin/admin.php):
- *    WP calls get_admin_page_parent() which scans $submenu for the slug. If it finds
- *    a match, it derives the hookname the same way as (1). If not found (because it
- *    was unset post-registration), it falls back to "admin_page_{slug}".
- *
- * When these two hooknames diverge, the render callback lives under name-A but WP
- * dispatches to name-B -- no handler found -- wp_die(403).
- *
- * The hide-by-unset pattern creates exactly this divergence:
- *   Registration:    parent found in $admin_page_hooks → "prautoblogger_page_prautoblogger-dossier"
- *   Post-unset:      slug absent from $submenu → "admin_page_prautoblogger-dossier" at request time
- *   Mismatch → 403.
- *
- * ## The fix: options.php-parent pattern
- *
- * options.php is a built-in WordPress admin page in $admin_page_hooks. Its key is
- * "settings" so a child page resolves to "settings_page_{slug}" at registration time --
- * BUT WordPress special-cases options.php children: get_admin_page_parent() returns
- * "options.php" directly (the page is always in the admin page hooks map and never
- * removed from $submenu by WP itself), so the hookname is "admin_page_{slug}" consistently
- * at both registration and request time. No $submenu mutation needed or permitted.
- *
- * ## Test strategy
- *
- * Brain\Monkey stubs WordPress functions. We cannot run a real WP request cycle in unit
- * tests, but we can replicate the request-time resolution algorithm precisely:
- *
- *   simulate_request_time_hookname($submenu_state, $slug):
- *     scan $submenu for $slug
- *     if found: return "{parent_key}_page_{slug}"   (same logic as registration-time)
- *     if not found: return "admin_page_{slug}"       (WP orphan fallback)
- *
- * This function is the discriminator. Against the v0.19.2 hide-by-unset implementation:
- *   - post-registration $submenu does NOT contain the slug (it was unset)
- *   - simulate_request_time_hookname returns "admin_page_prautoblogger-dossier"
- *   - but registration returned "prautoblogger_page_prautoblogger-dossier"
- *   - MISMATCH → test_request_time_hookname_matches_registration_hookname FAILS ✓
- *
- * Against the v0.19.3 options.php-parent fix:
- *   - $submenu is not mutated; the slug appears under options.php
- *   - simulate_request_time_hookname sees options.php as parent
- *   - registration also used options.php → both produce "admin_page_prautoblogger-dossier"
- *   - MATCH → test passes ✓
- *
- * Additional tests:
- *   - Parent slug must be PARENT_SLUG constant ('options.php')
- *   - No $submenu mutation after registration
- *   - Deep-link URLs are parent-agnostic (admin.php?page=...&post_id=N unchanged)
- *   - Asset enqueue gate uses 'admin_page_' prefix (not 'prautoblogger_page_')
+ * @see DossierHooknameMechanismTest -- request-time discriminator + regression proof.
+ * @see ARCHITECTURE.md             -- §22b (hidden admin page convention).
+ * @see CONVENTIONS.md              -- §Hidden Admin Pages.
  *
  * @package PRAutoBlogger\Tests\Admin
  */
 
 namespace PRAutoBlogger\Tests\Admin;
 
-use PRAutoBlogger\Tests\BaseTestCase;
 use Brain\Monkey;
 use Brain\Monkey\Functions;
 
-class DossierMenuRegistrationTest extends BaseTestCase {
-
-	/** @var array<int, string> Call sequence spy. */
-	private array $call_sequence = [];
-
-	/**
-	 * Captured parent slug from the most recent add_submenu_page call.
-	 *
-	 * @var string|null
-	 */
-	private ?string $captured_parent_slug = null;
-
-	/**
-	 * Captured menu slug from the most recent add_submenu_page call.
-	 *
-	 * @var string|null
-	 */
-	private ?string $captured_menu_slug = null;
-
-	/**
-	 * Hookname returned by the most recent add_submenu_page call.
-	 *
-	 * In real WordPress this is `{parent_key}_page_{slug}` when parent is known,
-	 * or `admin_page_{slug}` when parent is not in $admin_page_hooks. For options.php
-	 * children WordPress always emits `admin_page_{slug}`.
-	 *
-	 * @var string|null
-	 */
-	private ?string $registration_hookname = null;
-
-	protected function setUp(): void {
-		parent::setUp();
-		$this->call_sequence         = [];
-		$this->captured_parent_slug  = null;
-		$this->captured_menu_slug    = null;
-		$this->registration_hookname = null;
-
-		// Spy stub: tracks call order, captures slugs, returns a hookname that
-		// reflects how WordPress actually resolves it for known parents.
-		Functions\when( 'add_menu_page' )->alias(
-			function () {
-				$this->call_sequence[] = 'add_menu_page';
-				return 'prautoblogger-settings';
-			}
-		);
-
-		// Simulate WordPress hookname computation:
-		// - options.php parent  → 'admin_page_{slug}'  (WP built-in; options.php children always resolve here)
-		// - known plugin parent → '{parent_key}_page_{slug}'
-		// - unknown parent      → 'admin_page_{slug}'  (orphan fallback)
-		Functions\when( 'add_submenu_page' )->alias(
-			function (
-				string $parent_slug,
-				string $page_title,
-				string $menu_title,
-				string $capability,
-				string $menu_slug,
-				$callback = ''
-			) {
-				$this->call_sequence[]       = 'add_submenu_page:' . $parent_slug . ':' . $menu_slug;
-				$this->captured_parent_slug  = $parent_slug;
-				$this->captured_menu_slug    = $menu_slug;
-
-				// Replicate WordPress hookname logic:
-				// options.php-parent pages always resolve to admin_page_{slug}.
-				// Plugin-parent pages (like prautoblogger-settings) resolve to
-				// {parent_key}_page_{slug} at registration time.
-				if ( 'options.php' === $parent_slug ) {
-					$hookname = 'admin_page_' . $menu_slug;
-				} else {
-					// Derive parent key: strip .php extension if present, then
-					// replace - with _ for the namespace prefix.
-					$parent_key = str_replace( '.php', '', $parent_slug );
-					$hookname   = $parent_key . '_page_' . $menu_slug;
-				}
-
-				$this->registration_hookname = $hookname;
-
-				// Populate $submenu to simulate what WordPress does at registration time.
-				// This is the state that get_admin_page_parent() scans at request time.
-				// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- test simulation.
-				global $submenu;
-				$submenu[ $parent_slug ]   = $submenu[ $parent_slug ] ?? array();
-				$submenu[ $parent_slug ][] = array( $page_title, $capability, $menu_slug, $menu_title );
-
-				return $hookname;
-			}
-		);
-
-		Functions\when( 'current_user_can' )->justReturn( true );
-		Functions\when( 'get_option' )->justReturn( false );
-		Functions\when( 'admin_url' )->alias(
-			function ( string $path = '' ) {
-				return 'https://example.com/wp-admin/' . ltrim( $path, '/' );
-			}
-		);
-		Functions\when( '__' )->returnArg( 1 );
-
-		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- test isolation.
-		$GLOBALS['submenu'] = array();
-	}
-
-	protected function tearDown(): void {
-		$this->call_sequence        = [];
-		$this->captured_parent_slug = null;
-		$this->captured_menu_slug   = null;
-		$this->registration_hookname = null;
-		unset( $GLOBALS['submenu'] );
-		parent::tearDown();
-	}
-
-	// =========================================================================
-	// § REQUEST-TIME HOOKNAME FAITHFULNESS
-	// The primary regression guard for the 403 incident class.
-	// =========================================================================
-
-	/**
-	 * Simulate the request-time hookname resolution algorithm.
-	 *
-	 * Replicates get_admin_page_parent() + the hookname derivation in
-	 * wp-admin/admin.php::wp_admin_canonical_url() / do_action("admin_{$page}"):
-	 *
-	 *   scan $submenu for the slug
-	 *   if found at parent P → return hookname derived from P
-	 *   if not found          → return "admin_page_{slug}"
-	 *
-	 * This is the discriminator function: it WILL return a different hookname than
-	 * add_submenu_page returned when the slug has been unset from $submenu.
-	 *
-	 * @param array<string, array<int, array<int, string>>> $submenu_state $submenu after all registration + mutations.
-	 * @param string                                        $slug          Page slug to resolve.
-	 * @return string Request-time hookname.
-	 */
-	private function simulate_request_time_hookname( array $submenu_state, string $slug ): string {
-		foreach ( $submenu_state as $parent => $items ) {
-			foreach ( $items as $item ) {
-				if ( isset( $item[2] ) && $slug === $item[2] ) {
-					// Found the slug; derive hookname the same way as registration.
-					if ( 'options.php' === $parent ) {
-						return 'admin_page_' . $slug;
-					}
-					$parent_key = str_replace( '.php', '', $parent );
-					return $parent_key . '_page_' . $slug;
-				}
-			}
-		}
-		// Slug absent from $submenu -- WP falls back to the orphan namespace.
-		return 'admin_page_' . $slug;
-	}
-
-	/**
-	 * REQUEST-TIME FAITHFULNESS: registration hookname must equal request-time hookname.
-	 *
-	 * This test directly discriminates the two patterns:
-	 *
-	 *   HIDE-BY-UNSET (v0.19.2, BROKEN):
-	 *     - add_submenu_page('prautoblogger-settings', ...) → 'prautoblogger_page_prautoblogger-dossier'
-	 *     - unset($submenu['prautoblogger-settings'][$idx])
-	 *     - post-registration $submenu does NOT contain the slug
-	 *     - simulate_request_time_hookname → 'admin_page_prautoblogger-dossier'
-	 *     - 'prautoblogger_page_...' ≠ 'admin_page_...' → FAIL ✓ (test correctly detects broken state)
-	 *
-	 *   OPTIONS.PHP-PARENT (v0.19.3, FIXED):
-	 *     - add_submenu_page('options.php', ...) → 'admin_page_prautoblogger-dossier'
-	 *     - no $submenu mutation
-	 *     - simulate_request_time_hookname → 'admin_page_prautoblogger-dossier'
-	 *     - MATCH → PASS ✓
-	 *
-	 * This test ALSO fails if any future change reintroduces $submenu mutation,
-	 * or switches back to a plugin-owned parent without preserving the submenu entry.
-	 */
-	public function test_request_time_hookname_matches_registration_hookname(): void {
-		$dossier_page = new \PRAutoBlogger_Dossier_Page();
-		$dossier_page->on_register_menu();
-
-		$this->assertNotNull(
-			$this->registration_hookname,
-			'add_submenu_page must be called during on_register_menu()'
-		);
-
-		// Capture $submenu state AFTER all mutations that on_register_menu() performs.
-		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- test read.
-		global $submenu;
-		$submenu_after = $submenu;
-
-		$request_time_hookname = $this->simulate_request_time_hookname(
-			$submenu_after,
-			\PRAutoBlogger_Dossier_Page::PAGE_SLUG
-		);
-
-		$this->assertSame(
-			$this->registration_hookname,
-			$request_time_hookname,
-			sprintf(
-				'Hookname mismatch: registration="%s", request-time="%s". '
-				. 'This is the 403 failure class. '
-				. 'The hide-by-unset pattern unsets the slug from $submenu after registration, '
-				. 'so get_admin_page_parent() fails at request time, WP recomputes under '
-				. 'the orphan "admin_page_*" namespace, finds no registered handler, '
-				. 'and calls wp_die(403). Fix: use options.php as parent -- hookname is '
-				. '"admin_page_{slug}" at both registration and request time, no mutation needed.',
-				$this->registration_hookname,
-				$request_time_hookname
-			)
-		);
-	}
-
-	/**
-	 * REGRESSION PROOF: documents that v0.19.2 hide-by-unset would have failed the
-	 * request-time test above.
-	 *
-	 * Directly simulates the broken implementation, applies simulate_request_time_hookname,
-	 * and asserts the MISMATCH -- proving the discriminator is effective.
-	 *
-	 * This test documents the failure state and serves as evidence that the test methodology
-	 * is correct. It passes by verifying the broken pattern produces the wrong hookname.
-	 */
-	public function test_hide_by_unset_would_fail_request_time_check(): void {
-		// --- SIMULATE V0.19.2 hide-by-unset IMPLEMENTATION ---
-		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- test simulation.
-		global $submenu;
-
-		// Step 1: Registration (add_submenu_page with plugin parent).
-		// Real add_submenu_page stub returns 'prautoblogger_page_prautoblogger-dossier'
-		// when parent is 'prautoblogger-settings'. Populate $submenu as WP does.
-		$broken_parent_slug = 'prautoblogger-settings';
-		$slug               = 'prautoblogger-dossier';
-
-		$submenu[ $broken_parent_slug ]   = $submenu[ $broken_parent_slug ] ?? array();
-		$submenu[ $broken_parent_slug ][] = array( 'Article Dossier', 'manage_options', $slug, 'Dossier' );
-
-		// The hookname WP computed at registration time with plugin-owned parent:
-		$broken_registration_hookname = 'prautoblogger_page_' . $slug;
-
-		// Step 2: The unset mutation (the bug).
-		// This is what v0.19.2's on_register_menu() did after add_submenu_page.
-		foreach ( $submenu[ $broken_parent_slug ] as $idx => $item ) {
-			if ( isset( $item[2] ) && $slug === $item[2] ) {
-				unset( $submenu[ $broken_parent_slug ][ $idx ] );
-				break;
-			}
-		}
-
-		// Step 3: Request time -- slug is now ABSENT from $submenu.
-		$request_time_hookname = $this->simulate_request_time_hookname( $submenu, $slug );
-
-		// THE MISMATCH that caused the 403:
-		$this->assertNotSame(
-			$broken_registration_hookname,
-			$request_time_hookname,
-			'Test methodology error: hide-by-unset must produce a hookname mismatch. '
-			. 'If this assertion fails the discriminator is broken.'
-		);
-
-		// Specifically: request-time falls back to admin_page_* orphan namespace.
-		$this->assertSame(
-			'admin_page_' . $slug,
-			$request_time_hookname,
-			'Request-time fallback must be admin_page_{slug} when slug absent from $submenu.'
-		);
-		$this->assertSame(
-			'prautoblogger_page_' . $slug,
-			$broken_registration_hookname,
-			'Registration-time hookname with prautoblogger-settings parent must be prautoblogger_page_{slug}.'
-		);
-	}
+class DossierMenuRegistrationTest extends DossierMenuRegistrationTestCase {
 
 	// =========================================================================
 	// § STRUCTURAL INVARIANTS
diff --git a/tests/unit/Admin/DossierMenuRegistrationTestCase.php b/tests/unit/Admin/DossierMenuRegistrationTestCase.php
new file mode 100644
index 0000000..7f06bcb
--- /dev/null
+++ b/tests/unit/Admin/DossierMenuRegistrationTestCase.php
@@ -0,0 +1,120 @@
+<?php
+/**
+ * Shared test harness for Dossier menu registration test suites.
+ *
+ * Provides the Brain\Monkey spy stubs (add_menu_page, add_submenu_page) and the
+ * $submenu isolation that both DossierMenuRegistrationTest and
+ * DossierHooknameMechanismTest depend on.
+ *
+ * @package PRAutoBlogger\Tests\Admin
+ */
+
+namespace PRAutoBlogger\Tests\Admin;
+
+use PRAutoBlogger\Tests\BaseTestCase;
+use Brain\Monkey\Functions;
+
+abstract class DossierMenuRegistrationTestCase extends BaseTestCase {
+
+	/** @var array<int, string> Call sequence spy. */
+	protected array $call_sequence = [];
+
+	/**
+	 * Captured parent slug from the most recent add_submenu_page call.
+	 *
+	 * @var string|null
+	 */
+	protected ?string $captured_parent_slug = null;
+
+	/**
+	 * Captured menu slug from the most recent add_submenu_page call.
+	 *
+	 * @var string|null
+	 */
+	protected ?string $captured_menu_slug = null;
+
+	/**
+	 * Hookname returned by the most recent add_submenu_page call.
+	 *
+	 * In real WordPress this is `{parent_key}_page_{slug}` when parent is known,
+	 * or `admin_page_{slug}` when parent is not in $admin_page_hooks. For options.php
+	 * children WordPress always emits `admin_page_{slug}`.
+	 *
+	 * @var string|null
+	 */
+	protected ?string $registration_hookname = null;
+
+	protected function setUp(): void {
+		parent::setUp();
+		$this->call_sequence         = [];
+		$this->captured_parent_slug  = null;
+		$this->captured_menu_slug    = null;
+		$this->registration_hookname = null;
+
+		// Spy stub: tracks call order, captures slugs, returns a hookname that
+		// reflects how WordPress actually resolves it for known parents.
+		Functions\when( 'add_menu_page' )->alias(
+			function () {
+				$this->call_sequence[] = 'add_menu_page';
+				return 'prautoblogger-settings';
+			}
+		);
+
+		// Simulate WordPress hookname computation:
+		// - options.php parent  → 'admin_page_{slug}'
+		// - known plugin parent → '{parent_key}_page_{slug}'
+		// - unknown parent      → 'admin_page_{slug}' (orphan fallback)
+		Functions\when( 'add_submenu_page' )->alias(
+			function (
+				string $parent_slug,
+				string $page_title,
+				string $menu_title,
+				string $capability,
+				string $menu_slug,
+				$callback = ''
+			) {
+				$this->call_sequence[]      = 'add_submenu_page:' . $parent_slug . ':' . $menu_slug;
+				$this->captured_parent_slug = $parent_slug;
+				$this->captured_menu_slug   = $menu_slug;
+
+				if ( 'options.php' === $parent_slug ) {
+					$hookname = 'admin_page_' . $menu_slug;
+				} else {
+					$parent_key = str_replace( '.php', '', $parent_slug );
+					$hookname   = $parent_key . '_page_' . $menu_slug;
+				}
+
+				$this->registration_hookname = $hookname;
+
+				// Populate $submenu as WordPress does at registration time.
+				// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- test simulation.
+				global $submenu;
+				$submenu[ $parent_slug ]   = $submenu[ $parent_slug ] ?? array();
+				$submenu[ $parent_slug ][] = array( $page_title, $capability, $menu_slug, $menu_title );
+
+				return $hookname;
+			}
+		);
+
+		Functions\when( 'current_user_can' )->justReturn( true );
+		Functions\when( 'get_option' )->justReturn( false );
+		Functions\when( 'admin_url' )->alias(
+			function ( string $path = '' ) {
+				return 'https://example.com/wp-admin/' . ltrim( $path, '/' );
+			}
+		);
+		Functions\when( '__' )->returnArg( 1 );
+
+		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- test isolation.
+		$GLOBALS['submenu'] = array();
+	}
+
+	protected function tearDown(): void {
+		$this->call_sequence         = [];
+		$this->captured_parent_slug  = null;
+		$this->captured_menu_slug    = null;
+		$this->registration_hookname = null;
+		unset( $GLOBALS['submenu'] );
+		parent::tearDown();
+	}
+}