test(admin): cover translation picker page url helpers

Adds 9 cases against MslsTranslationPickerPage's static helpers:

- page_slug() composes msls-translation-picker-<post_type>
- parent_slug() returns 'edit.php' for 'post', edit.php?post_type=X
  otherwise, and '' for empty input
- url() routes through admin_url + add_query_arg
- save_per_page_option() sanitises ints, falls back to PER_PAGE_DEFAULT
  for non-positive values, and is a no-op for unrelated options

Author: apermo

tests/phpunit/TestMslsTranslationPickerPage.php

@@ -0,0 +1,92 @@
+<?php declare( strict_types=1 );
+
+namespace lloc\MslsTests;
+
+use Brain\Monkey\Functions;
+use lloc\Msls\MslsTranslationPickerPage;
+
+final class TestMslsTranslationPickerPage extends MslsUnitTestCase {
+
+	public function test_page_slug_includes_post_type(): void {
+		$this->assertSame( 'msls-translation-picker-post', MslsTranslationPickerPage::page_slug( 'post' ) );
+		$this->assertSame( 'msls-translation-picker-page', MslsTranslationPickerPage::page_slug( 'page' ) );
+		$this->assertSame( 'msls-translation-picker-event', MslsTranslationPickerPage::page_slug( 'event' ) );
+	}
+
+	public function test_parent_slug_for_built_in_post(): void {
+		$this->assertSame( 'edit.php', MslsTranslationPickerPage::parent_slug( 'post' ) );
+	}
+
+	public function test_parent_slug_for_other_post_types(): void {
+		$this->assertSame( 'edit.php?post_type=page', MslsTranslationPickerPage::parent_slug( 'page' ) );
+		$this->assertSame( 'edit.php?post_type=event', MslsTranslationPickerPage::parent_slug( 'event' ) );
+	}
+
+	public function test_parent_slug_for_empty_post_type(): void {
+		$this->assertSame( '', MslsTranslationPickerPage::parent_slug( '' ) );
+	}
+
+	public function test_url_uses_admin_url_and_query_arg(): void {
+		Functions\expect( 'admin_url' )
+			->once()
+			->with( 'edit.php' )
+			->andReturn( 'https://example.tld/wp-admin/edit.php' );
+
+		Functions\expect( 'add_query_arg' )
+			->once()
+			->andReturnUsing(
+				function ( $args, $url ) {
+					return $url . '?' . http_build_query( $args );
+				}
+			);
+
+		$result = MslsTranslationPickerPage::url( 'post' );
+
+		$this->assertSame(
+			'https://example.tld/wp-admin/edit.php?page=msls-translation-picker-post',
+			$result
+		);
+	}
+
+	public function test_url_for_non_post_post_type_routes_through_typed_parent(): void {
+		Functions\expect( 'admin_url' )
+			->once()
+			->with( 'edit.php?post_type=page' )
+			->andReturn( 'https://example.tld/wp-admin/edit.php?post_type=page' );
+
+		Functions\expect( 'add_query_arg' )
+			->once()
+			->andReturnUsing(
+				function ( $args, $url ) {
+					return $url . '&' . http_build_query( $args );
+				}
+			);
+
+		$result = MslsTranslationPickerPage::url( 'page' );
+
+		$this->assertSame(
+			'https://example.tld/wp-admin/edit.php?post_type=page&page=msls-translation-picker-page',
+			$result
+		);
+	}
+
+	public function test_save_per_page_option_returns_int_for_picker_option(): void {
+		$this->assertSame(
+			42,
+			MslsTranslationPickerPage::save_per_page_option( false, 'msls_tp_per_page', '42' )
+		);
+	}
+
+	public function test_save_per_page_option_falls_back_for_non_positive(): void {
+		$this->assertSame(
+			MslsTranslationPickerPage::PER_PAGE_DEFAULT,
+			MslsTranslationPickerPage::save_per_page_option( false, 'msls_tp_per_page', '0' )
+		);
+	}
+
+	public function test_save_per_page_option_passes_through_other_options(): void {
+		$this->assertFalse(
+			MslsTranslationPickerPage::save_per_page_option( false, 'unrelated_option', '5' )
+		);
+	}
+}