first commit

cache/tests/administration_helper_test.php

@@ -0,0 +1,271 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace core_cache;
+
+use cache_config_testing;
+use cache_config_writer;
+use cache_factory;
+use cache_helper;
+use cache_store;
+
+defined('MOODLE_INTERNAL') || die();
+
+// Include the necessary evils.
+global $CFG;
+require_once($CFG->dirroot.'/cache/locallib.php');
+require_once($CFG->dirroot.'/cache/tests/fixtures/lib.php');
+
+
+/**
+ * PHPunit tests for the cache API and in particular the core_cache\administration_helper
+ *
+ * @package    core_cache
+ * @category   test
+ * @copyright  2012 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class administration_helper_test extends \advanced_testcase {
+
+    /**
+     * Set things back to the default before each test.
+     */
+    public function setUp(): void {
+        parent::setUp();
+        cache_factory::reset();
+        cache_config_testing::create_default_configuration();
+    }
+
+    /**
+     * Final task is to reset the cache system
+     */
+    public static function tearDownAfterClass(): void {
+        parent::tearDownAfterClass();
+        cache_factory::reset();
+    }
+
+    /**
+     * Test the numerous summaries the helper can produce.
+     */
+    public function test_get_summaries(): void {
+        // First the preparation.
+        $config = cache_config_writer::instance();
+        $this->assertTrue($config->add_store_instance('summariesstore', 'file'));
+        $config->set_definition_mappings('core/eventinvalidation', array('summariesstore'));
+        $this->assertTrue($config->set_mode_mappings(array(
+            cache_store::MODE_APPLICATION => array('summariesstore'),
+            cache_store::MODE_SESSION => array('default_session'),
+            cache_store::MODE_REQUEST => array('default_request'),
+        )));
+
+        $storesummaries = administration_helper::get_store_instance_summaries();
+        $this->assertIsArray($storesummaries);
+        $this->assertArrayHasKey('summariesstore', $storesummaries);
+        $summary = $storesummaries['summariesstore'];
+        // Check the keys
+        $this->assertArrayHasKey('name', $summary);
+        $this->assertArrayHasKey('plugin', $summary);
+        $this->assertArrayHasKey('default', $summary);
+        $this->assertArrayHasKey('isready', $summary);
+        $this->assertArrayHasKey('requirementsmet', $summary);
+        $this->assertArrayHasKey('mappings', $summary);
+        $this->assertArrayHasKey('modes', $summary);
+        $this->assertArrayHasKey('supports', $summary);
+        // Check the important/known values
+        $this->assertEquals('summariesstore', $summary['name']);
+        $this->assertEquals('file', $summary['plugin']);
+        $this->assertEquals(0, $summary['default']);
+        $this->assertEquals(1, $summary['isready']);
+        $this->assertEquals(1, $summary['requirementsmet']);
+
+        // Find the number of mappings to sessionstore.
+        $mappingcount = count(array_filter($config->get_definitions(), function($element) {
+            return $element['mode'] === cache_store::MODE_APPLICATION;
+        }));
+        $this->assertEquals($mappingcount, $summary['mappings']);
+
+        $definitionsummaries = administration_helper::get_definition_summaries();
+        $this->assertIsArray($definitionsummaries);
+        $this->assertArrayHasKey('core/eventinvalidation', $definitionsummaries);
+        $summary = $definitionsummaries['core/eventinvalidation'];
+        // Check the keys
+        $this->assertArrayHasKey('id', $summary);
+        $this->assertArrayHasKey('name', $summary);
+        $this->assertArrayHasKey('mode', $summary);
+        $this->assertArrayHasKey('component', $summary);
+        $this->assertArrayHasKey('area', $summary);
+        $this->assertArrayHasKey('mappings', $summary);
+        // Check the important/known values
+        $this->assertEquals('core/eventinvalidation', $summary['id']);
+        $this->assertInstanceOf('lang_string', $summary['name']);
+        $this->assertEquals(cache_store::MODE_APPLICATION, $summary['mode']);
+        $this->assertEquals('core', $summary['component']);
+        $this->assertEquals('eventinvalidation', $summary['area']);
+        $this->assertIsArray($summary['mappings']);
+        $this->assertContains('summariesstore', $summary['mappings']);
+
+        $pluginsummaries = administration_helper::get_store_plugin_summaries();
+        $this->assertIsArray($pluginsummaries);
+        $this->assertArrayHasKey('file', $pluginsummaries);
+        $summary = $pluginsummaries['file'];
+        // Check the keys
+        $this->assertArrayHasKey('name', $summary);
+        $this->assertArrayHasKey('requirementsmet', $summary);
+        $this->assertArrayHasKey('instances', $summary);
+        $this->assertArrayHasKey('modes', $summary);
+        $this->assertArrayHasKey('supports', $summary);
+        $this->assertArrayHasKey('canaddinstance', $summary);
+
+        $locksummaries = administration_helper::get_lock_summaries();
+        $this->assertIsArray($locksummaries);
+        $this->assertTrue(count($locksummaries) > 0);
+
+        $mappings = administration_helper::get_default_mode_stores();
+        $this->assertIsArray($mappings);
+        $this->assertCount(3, $mappings);
+        $this->assertArrayHasKey(cache_store::MODE_APPLICATION, $mappings);
+        $this->assertIsArray($mappings[cache_store::MODE_APPLICATION]);
+        $this->assertContains('summariesstore', $mappings[cache_store::MODE_APPLICATION]);
+
+        $potentials = administration_helper::get_definition_store_options('core', 'eventinvalidation');
+        $this->assertIsArray($potentials); // Currently used, suitable, default
+        $this->assertCount(3, $potentials);
+        $this->assertArrayHasKey('summariesstore', $potentials[0]);
+        $this->assertArrayHasKey('summariesstore', $potentials[1]);
+        $this->assertArrayHasKey('default_application', $potentials[1]);
+    }
+
+    /**
+     * Test instantiating an add store form.
+     */
+    public function test_get_add_store_form(): void {
+        $form = cache_factory::get_administration_display_helper()->get_add_store_form('file');
+        $this->assertInstanceOf('moodleform', $form);
+
+        try {
+            $form = cache_factory::get_administration_display_helper()->get_add_store_form('somethingstupid');
+            $this->fail('You should not be able to create an add form for a store plugin that does not exist.');
+        } catch (\moodle_exception $e) {
+            $this->assertInstanceOf('coding_exception', $e, 'Needs to be: ' .get_class($e)." ::: ".$e->getMessage());
+        }
+    }
+
+    /**
+     * Test instantiating a form to edit a store instance.
+     */
+    public function test_get_edit_store_form(): void {
+        // Always instantiate a new core display helper here.
+        $administrationhelper = new local\administration_display_helper;
+        $config = cache_config_writer::instance();
+        $this->assertTrue($config->add_store_instance('test_get_edit_store_form', 'file'));
+
+        $form = $administrationhelper->get_edit_store_form('file', 'test_get_edit_store_form');
+        $this->assertInstanceOf('moodleform', $form);
+
+        try {
+            $form = $administrationhelper->get_edit_store_form('somethingstupid', 'moron');
+            $this->fail('You should not be able to create an edit form for a store plugin that does not exist.');
+        } catch (\moodle_exception $e) {
+            $this->assertInstanceOf('coding_exception', $e);
+        }
+
+        try {
+            $form = $administrationhelper->get_edit_store_form('file', 'blisters');
+            $this->fail('You should not be able to create an edit form for a store plugin that does not exist.');
+        } catch (\moodle_exception $e) {
+            $this->assertInstanceOf('coding_exception', $e);
+        }
+    }
+
+    /**
+     * Test the hash_key functionality.
+     */
+    public function test_hash_key(): void {
+        $this->resetAfterTest();
+        set_debugging(DEBUG_ALL);
+
+        // First with simplekeys
+        $instance = cache_config_testing::instance(true);
+        $instance->phpunit_add_definition('phpunit/hashtest', array(
+            'mode' => cache_store::MODE_APPLICATION,
+            'component' => 'phpunit',
+            'area' => 'hashtest',
+            'simplekeys' => true
+        ));
+        $factory = cache_factory::instance();
+        $definition = $factory->create_definition('phpunit', 'hashtest');
+
+        $result = cache_helper::hash_key('test', $definition);
+        $this->assertEquals('test-'.$definition->generate_single_key_prefix(), $result);
+
+        try {
+            cache_helper::hash_key('test/test', $definition);
+            $this->fail('Invalid key was allowed, you should see this.');
+        } catch (\coding_exception $e) {
+            $this->assertEquals('test/test', $e->debuginfo);
+        }
+
+        // Second without simple keys
+        $instance->phpunit_add_definition('phpunit/hashtest2', array(
+            'mode' => cache_store::MODE_APPLICATION,
+            'component' => 'phpunit',
+            'area' => 'hashtest2',
+            'simplekeys' => false
+        ));
+        $definition = $factory->create_definition('phpunit', 'hashtest2');
+
+        $result = cache_helper::hash_key('test', $definition);
+        $this->assertEquals(sha1($definition->generate_single_key_prefix().'-test'), $result);
+
+        $result = cache_helper::hash_key('test/test', $definition);
+        $this->assertEquals(sha1($definition->generate_single_key_prefix().'-test/test'), $result);
+    }
+
+    /**
+     * Tests the get_usage function.
+     */
+    public function test_get_usage(): void {
+        // Create a test cache definition and put items in it.
+        $instance = cache_config_testing::instance(true);
+        $instance->phpunit_add_definition('phpunit/test', [
+                'mode' => cache_store::MODE_APPLICATION,
+                'component' => 'phpunit',
+                'area' => 'test',
+                'simplekeys' => true
+        ]);
+        $cache = \cache::make('phpunit', 'test');
+        for ($i = 0; $i < 100; $i++) {
+            $cache->set('key' . $i, str_repeat('x', $i));
+        }
+
+        $factory = cache_factory::instance();
+        $adminhelper = $factory->get_administration_display_helper();
+
+        $usage = $adminhelper->get_usage(10)['phpunit/test'];
+        $this->assertEquals('phpunit/test', $usage->cacheid);
+        $this->assertCount(1, $usage->stores);
+        $store = $usage->stores[0];
+        $this->assertEquals('default_application', $store->name);
+        $this->assertEquals('cachestore_file', $store->class);
+        $this->assertEquals(true, $store->supported);
+        $this->assertEquals(100, $store->items);
+
+        // As file store checks all items, the values should be exact.
+        $this->assertEqualsWithDelta(57.4, $store->mean, 0.1);
+        $this->assertEqualsWithDelta(29.0, $store->sd, 0.1);
+        $this->assertEquals(0, $store->margin);
+    }
+}

cache/tests/allow_temporary_caches_test.php

@@ -0,0 +1,99 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace core_cache;
+
+/**
+ * Unit tests for {@see allow_temporary_caches}.
+ *
+ * @package core_cache
+ * @category test
+ * @copyright 2022 The Open University
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ * @covers \core_cache\allow_temporary_caches
+ */
+class allow_temporary_caches_test extends \advanced_testcase {
+
+    /**
+     * Tests whether temporary caches are allowed.
+     */
+    public function test_is_allowed(): void {
+        // Not allowed by default.
+        $this->assertFalse(allow_temporary_caches::is_allowed());
+
+        // Allowed if we have an instance.
+        $frog = new allow_temporary_caches();
+        $this->assertTrue(allow_temporary_caches::is_allowed());
+
+        // Or two instances.
+        $toad = new allow_temporary_caches();
+        $this->assertTrue(allow_temporary_caches::is_allowed());
+
+        // Get rid of the instances.
+        unset($frog);
+        $this->assertTrue(allow_temporary_caches::is_allowed());
+
+        // Not allowed when we get back to no instances.
+        unset($toad);
+        $this->assertFalse(allow_temporary_caches::is_allowed());
+
+        // Check it works to automatically free up the instance when variable goes out of scope.
+        $this->inner_is_allowed();
+        $this->assertFalse(allow_temporary_caches::is_allowed());
+    }
+
+    /**
+     * Function call to demonstrate that you don't need to manually unset the variable.
+     */
+    protected function inner_is_allowed(): void {
+        $gecko = new allow_temporary_caches();
+        $this->assertTrue(allow_temporary_caches::is_allowed());
+    }
+
+    /**
+     * Tests that the temporary caches actually work, including normal and versioned get and set.
+     */
+    public function test_temporary_cache(): void {
+        $this->resetAfterTest();
+
+        // Disable the cache.
+        \cache_phpunit_factory::phpunit_disable();
+        try {
+            // Try using the cache now - it returns false/null for everything.
+            $cache = \cache::make('core', 'coursemodinfo');
+            $cache->set('frog', 'ribbit');
+            $this->assertFalse($cache->get('frog'));
+            $cache->set_versioned('toad', 2, 'croak');
+            $this->assertFalse($cache->get_versioned('toad', 2));
+
+            // But when we allow temporary caches, it should work as normal.
+            $allow = new allow_temporary_caches();
+            $cache = \cache::make('core', 'coursemodinfo');
+            $cache->set('frog', 'ribbit');
+            $this->assertEquals('ribbit', $cache->get('frog'));
+            $cache->set_versioned('toad', 2, 'croak');
+            $this->assertEquals('croak', $cache->get_versioned('toad', 2));
+
+            // Let's actually use modinfo, to check it works with locking too.
+            $course = $this->getDataGenerator()->create_course();
+            get_fast_modinfo($course);
+        } finally {
+            // You have to do this after phpunit_disable or it breaks later tests.
+            \cache_factory::reset();
+            \cache_factory::instance(true);
+        }
+    }
+}

cache/tests/behat/perf_info.feature

@@ -0,0 +1,21 @@
+@core @core_cache
+Feature: Display cache information in performance info
+  In order to investigate performance problems with caching
+  As an administrator
+  I need to be able to see cache information in perfinfo
+
+  Background:
+    Given the following config values are set as admin:
+      | perfdebug | 15 |
+    And the following "courses" exist:
+      | fullname | shortname |
+      | Course 1 | C1        |
+
+  Scenario: Cache performance info displays
+    When I am on the "C1" "Course" page logged in as "admin"
+    # Confirm that the first cache info table is visible by checking an arbitrary row.
+    Then I should see "default_application" in the "core/databasemeta" "table_row"
+    # Don't specify the exact size as it may vary.
+    And I should see "KB" in the "core/databasemeta" "table_row"
+    # Confirm that the second cache info table is visible.
+    And I should see "default_application" in the "cachestore_file" "table_row"

cache/tests/behat/siteadmin_cache_breadcrumbs.feature

@@ -0,0 +1,27 @@
+@core @core_cache @javascript
+Feature: Verify the breadcrumbs in different cache site administration pages
+  Whenever I navigate to caching configuration page in site administration
+  As an admin
+  The breadcrumbs should be visible
+
+  Background:
+    Given I log in as "admin"
+
+  Scenario: Verify the breadcrumbs in caching configuration, add assistance, edit mappings and edit sharings page as an admin
+    Given I navigate to "Plugins > Caching > Configuration" in site administration
+    And "Configuration" "text" should exist in the ".breadcrumb" "css_element"
+    And "Caching" "link" should exist in the ".breadcrumb" "css_element"
+    When I click on "Add instance" "link"
+    Then "Add cache store" "text" should exist in the ".breadcrumb" "css_element"
+    And "Configuration" "link" should exist in the ".breadcrumb" "css_element"
+    And "Caching" "link" should exist in the ".breadcrumb" "css_element"
+    And I press "Cancel"
+    And I click on "Edit mappings" "link"
+    And "Edit definition mapping" "text" should exist in the ".breadcrumb" "css_element"
+    And "Configuration" "link" should exist in the ".breadcrumb" "css_element"
+    And "Caching" "link" should exist in the ".breadcrumb" "css_element"
+    And I press "Cancel"
+    And I click on "Edit sharing" "link"
+    And "Edit definition sharing" "text" should exist in the ".breadcrumb" "css_element"
+    And "Configuration" "link" should exist in the ".breadcrumb" "css_element"
+    And "Caching" "link" should exist in the ".breadcrumb" "css_element"

cache/tests/behat/usage.feature

@@ -0,0 +1,35 @@
+@core @core_cache
+Feature: Display usage information for cache
+  In order to investigate performance problems with caching
+  As an administrator
+  I need to be able to monitor the size of items in the cache
+
+  Background:
+    Given the following "courses" exist:
+      | fullname | shortname |
+      | Course 1 | C1        |
+
+  Scenario: Cache performance info displays
+    When I am on the "C1" "Course" page logged in as "admin"
+    And I navigate to "Plugins > Caching > Cache usage" in site administration
+
+    # Check one row of the summary table. The actual total is currently 3.6MB so it's likely to
+    # continue to be in the MB range.
+    Then "default_application" row "Plugin" column of "usage_summary" table should contain "cachestore_file"
+    And "default_application" row "Estimated total" column of "usage_summary" table should contain "MB"
+    And "default_application" row "Actual usage (if known)" column of "usage_summary" table should contain "MB"
+
+    # And one row of the main table. The totals are fixed to use the MB unit.
+    And "core/config" row "Store name" column of "usage_main" table should contain "default_application"
+    And "core/config" row "Plugin" column of "usage_main" table should contain "cachestore_file"
+    And "core/config" row "Estimated total" column of "usage_main" table should contain "MB"
+
+  Scenario: Sample option works
+    When I am on the "C1" "Course" page logged in as "admin"
+    And I navigate to "Plugins > Caching > Cache usage" in site administration
+    And I set the field "samples" to "1000"
+    And I press "Update"
+
+    Then the field "samples" matches value "1000"
+    And "usage_summary" "table" should exist
+    And "usage_main" "table" should exist

cache/tests/cache_helper_test.php

@@ -0,0 +1,64 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace core_cache;
+
+/**
+ * PHPunit tests for the cache_helper class.
+ *
+ * @package    core
+ * @category   cache
+ * @copyright  2023 Andrew Lyons <andrew@nicols.co.uk>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ * @coversDefaultClass \cache_helper
+ */
+class cache_helper_test extends \advanced_testcase {
+    /**
+     * Test the result_found method.
+     *
+     * @param mixed $value
+     * @param bool $expected
+     * @dataProvider result_found_provider
+     * @covers ::result_found
+     */
+    public function test_result_found($value, bool $expected): void {
+        $this->assertEquals($expected, \cache_helper::result_found($value));
+    }
+
+    /**
+     * Data provider for result_found tests.
+     *
+     * @return array
+     */
+    public function result_found_provider(): array {
+        return [
+            // Only false values are considered as not found.
+            [false, false],
+
+            // The rest are considered valid values.
+            [null, true],
+            [0, true],
+            ['', true],
+            [[], true],
+            [new \stdClass(), true],
+            [true, true],
+            [1, true],
+            ['a', true],
+            [[1], true],
+            [new \stdClass(), true],
+        ];
+    }
+}

cache/tests/config_writer_test.php

@@ -0,0 +1,287 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace core_cache;
+
+use cache_config_testing;
+use cache_config_writer;
+use cache_factory;
+use cache_store;
+
+defined('MOODLE_INTERNAL') || die();
+
+// Include the necessary evils.
+global $CFG;
+require_once($CFG->dirroot.'/cache/locallib.php');
+require_once($CFG->dirroot.'/cache/tests/fixtures/lib.php');
+
+/**
+ * PHPunit tests for the cache API and in particular the cache config writer.
+ *
+ * @package    core_cache
+ * @category   test
+ * @copyright  2012 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class config_writer_test extends \advanced_testcase {
+
+    /**
+     * Set things back to the default before each test.
+     */
+    public function setUp(): void {
+        parent::setUp();
+        cache_factory::reset();
+        cache_config_testing::create_default_configuration();
+    }
+
+    /**
+     * Final task is to reset the cache system
+     */
+    public static function tearDownAfterClass(): void {
+        parent::tearDownAfterClass();
+        cache_factory::reset();
+    }
+
+    /**
+     * Test getting an instance. Pretty basic.
+     */
+    public function test_instance(): void {
+        $config = cache_config_writer::instance();
+        $this->assertInstanceOf('cache_config_writer', $config);
+    }
+
+    /**
+     * Test the default configuration.
+     */
+    public function test_default_configuration(): void {
+        $config = cache_config_writer::instance();
+
+        // First check stores.
+        $stores = $config->get_all_stores();
+        $hasapplication = false;
+        $hassession = false;
+        $hasrequest = false;
+        foreach ($stores as $store) {
+            // Check the required keys.
+            $this->assertArrayHasKey('name', $store);
+            $this->assertArrayHasKey('plugin', $store);
+            $this->assertArrayHasKey('modes', $store);
+            $this->assertArrayHasKey('default', $store);
+            // Check the mode, we need at least one default store of each mode.
+            if (!empty($store['default'])) {
+                if ($store['modes'] & cache_store::MODE_APPLICATION) {
+                    $hasapplication = true;
+                }
+                if ($store['modes'] & cache_store::MODE_SESSION) {
+                    $hassession = true;
+                }
+                if ($store['modes'] & cache_store::MODE_REQUEST) {
+                    $hasrequest = true;
+                }
+            }
+        }
+        $this->assertTrue($hasapplication, 'There is no default application cache store.');
+        $this->assertTrue($hassession, 'There is no default session cache store.');
+        $this->assertTrue($hasrequest, 'There is no default request cache store.');
+
+        // Next check the definitions.
+        $definitions = $config->get_definitions();
+        $eventinvalidation = false;
+        foreach ($definitions as $definition) {
+            // Check the required keys.
+            $this->assertArrayHasKey('mode', $definition);
+            $this->assertArrayHasKey('component', $definition);
+            $this->assertArrayHasKey('area', $definition);
+            if ($definition['component'] === 'core' && $definition['area'] === 'eventinvalidation') {
+                $eventinvalidation = true;
+            }
+        }
+        $this->assertTrue($eventinvalidation, 'Missing the event invalidation definition.');
+
+        // Next mode mappings
+        $mappings = $config->get_mode_mappings();
+        $hasapplication = false;
+        $hassession = false;
+        $hasrequest = false;
+        foreach ($mappings as $mode) {
+            // Check the required keys.
+            $this->assertArrayHasKey('mode', $mode);
+            $this->assertArrayHasKey('store', $mode);
+
+            if ($mode['mode'] === cache_store::MODE_APPLICATION) {
+                $hasapplication = true;
+            }
+            if ($mode['mode'] === cache_store::MODE_SESSION) {
+                $hassession = true;
+            }
+            if ($mode['mode'] === cache_store::MODE_REQUEST) {
+                $hasrequest = true;
+            }
+        }
+        $this->assertTrue($hasapplication, 'There is no mapping for the application mode.');
+        $this->assertTrue($hassession, 'There is no mapping for the session mode.');
+        $this->assertTrue($hasrequest, 'There is no mapping for the request mode.');
+
+        // Finally check config locks
+        $locks = $config->get_locks();
+        foreach ($locks as $lock) {
+            $this->assertArrayHasKey('name', $lock);
+            $this->assertArrayHasKey('type', $lock);
+            $this->assertArrayHasKey('default', $lock);
+        }
+        // There has to be at least the default lock.
+        $this->assertTrue(count($locks) > 0);
+    }
+
+    /**
+     * Test updating the definitions.
+     */
+    public function test_update_definitions(): void {
+        $config = cache_config_writer::instance();
+        // Remove the definition.
+        $config->phpunit_remove_definition('core/string');
+        $definitions = $config->get_definitions();
+        // Check it is gone.
+        $this->assertFalse(array_key_exists('core/string', $definitions));
+        // Update definitions. This should re-add it.
+        cache_config_writer::update_definitions();
+        $definitions = $config->get_definitions();
+        // Check it is back again.
+        $this->assertTrue(array_key_exists('core/string', $definitions));
+    }
+
+    /**
+     * Test adding/editing/deleting store instances.
+     */
+    public function test_add_edit_delete_plugin_instance(): void {
+        $config = cache_config_writer::instance();
+        $this->assertArrayNotHasKey('addplugintest', $config->get_all_stores());
+        $this->assertArrayNotHasKey('addplugintestwlock', $config->get_all_stores());
+        // Add a default file instance.
+        $config->add_store_instance('addplugintest', 'file');
+
+        cache_factory::reset();
+        $config = cache_config_writer::instance();
+        $this->assertArrayHasKey('addplugintest', $config->get_all_stores());
+
+        // Add a store with a lock described.
+        $config->add_store_instance('addplugintestwlock', 'file', array('lock' => 'default_file_lock'));
+        $this->assertArrayHasKey('addplugintestwlock', $config->get_all_stores());
+
+        $config->delete_store_instance('addplugintest');
+        $this->assertArrayNotHasKey('addplugintest', $config->get_all_stores());
+        $this->assertArrayHasKey('addplugintestwlock', $config->get_all_stores());
+
+        $config->delete_store_instance('addplugintestwlock');
+        $this->assertArrayNotHasKey('addplugintest', $config->get_all_stores());
+        $this->assertArrayNotHasKey('addplugintestwlock', $config->get_all_stores());
+
+        // Add a default file instance.
+        $config->add_store_instance('storeconfigtest', 'file', array('test' => 'a', 'one' => 'two'));
+        $stores = $config->get_all_stores();
+        $this->assertArrayHasKey('storeconfigtest', $stores);
+        $this->assertArrayHasKey('configuration', $stores['storeconfigtest']);
+        $this->assertArrayHasKey('test', $stores['storeconfigtest']['configuration']);
+        $this->assertArrayHasKey('one', $stores['storeconfigtest']['configuration']);
+        $this->assertEquals('a', $stores['storeconfigtest']['configuration']['test']);
+        $this->assertEquals('two', $stores['storeconfigtest']['configuration']['one']);
+
+        $config->edit_store_instance('storeconfigtest', 'file', array('test' => 'b', 'one' => 'three'));
+        $stores = $config->get_all_stores();
+        $this->assertArrayHasKey('storeconfigtest', $stores);
+        $this->assertArrayHasKey('configuration', $stores['storeconfigtest']);
+        $this->assertArrayHasKey('test', $stores['storeconfigtest']['configuration']);
+        $this->assertArrayHasKey('one', $stores['storeconfigtest']['configuration']);
+        $this->assertEquals('b', $stores['storeconfigtest']['configuration']['test']);
+        $this->assertEquals('three', $stores['storeconfigtest']['configuration']['one']);
+
+        $config->delete_store_instance('storeconfigtest');
+
+        try {
+            $config->delete_store_instance('default_application');
+            $this->fail('Default store deleted. This should not be possible!');
+        } catch (\Exception $e) {
+            $this->assertInstanceOf('cache_exception', $e);
+        }
+
+        try {
+            $config->delete_store_instance('some_crazy_store');
+            $this->fail('You should not be able to delete a store that does not exist.');
+        } catch (\Exception $e) {
+            $this->assertInstanceOf('cache_exception', $e);
+        }
+
+        try {
+            // Try with a plugin that does not exist.
+            $config->add_store_instance('storeconfigtest', 'shallowfail', array('test' => 'a', 'one' => 'two'));
+            $this->fail('You should not be able to add an instance of a store that does not exist.');
+        } catch (\Exception $e) {
+            $this->assertInstanceOf('cache_exception', $e);
+        }
+    }
+
+    /**
+     * Test setting some mode mappings.
+     */
+    public function test_set_mode_mappings(): void {
+        $config = cache_config_writer::instance();
+        $this->assertTrue($config->add_store_instance('setmodetest', 'file'));
+        $this->assertTrue($config->set_mode_mappings(array(
+            cache_store::MODE_APPLICATION => array('setmodetest', 'default_application'),
+            cache_store::MODE_SESSION => array('default_session'),
+            cache_store::MODE_REQUEST => array('default_request'),
+        )));
+        $mappings = $config->get_mode_mappings();
+        $setmodetestfound = false;
+        foreach ($mappings as $mapping) {
+            if ($mapping['store'] == 'setmodetest' && $mapping['mode'] == cache_store::MODE_APPLICATION) {
+                $setmodetestfound = true;
+            }
+        }
+        $this->assertTrue($setmodetestfound, 'Set mapping did not work as expected.');
+    }
+
+    /**
+     * Test setting some definition mappings.
+     */
+    public function test_set_definition_mappings(): void {
+        $config = cache_config_testing::instance(true);
+        $config->phpunit_add_definition('phpunit/testdefinition', array(
+            'mode' => cache_store::MODE_APPLICATION,
+            'component' => 'phpunit',
+            'area' => 'testdefinition'
+        ));
+
+        $config = cache_config_writer::instance();
+        $this->assertTrue($config->add_store_instance('setdefinitiontest', 'file'));
+        $this->assertIsArray($config->get_definition_by_id('phpunit/testdefinition'));
+        $config->set_definition_mappings('phpunit/testdefinition', array('setdefinitiontest', 'default_application'));
+
+        try {
+            $config->set_definition_mappings('phpunit/testdefinition', array('something that does not exist'));
+            $this->fail('You should not be able to set a mapping for a store that does not exist.');
+        } catch (\Exception $e) {
+            $this->assertInstanceOf('coding_exception', $e);
+        }
+
+        try {
+            $config->set_definition_mappings('something/crazy', array('setdefinitiontest'));
+            $this->fail('You should not be able to set a mapping for a definition that does not exist.');
+        } catch (\Exception $e) {
+            $this->assertInstanceOf('coding_exception', $e);
+        }
+    }
+}

cache/tests/fixtures/cache_phpunit_dummy_datasource_versionable.php

@@ -0,0 +1,84 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * A dummy datasource which supports versioning.
+ *
+ * @package core_cache
+ * @copyright 2021 The Open University
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cache_phpunit_dummy_datasource_versionable extends cache_phpunit_dummy_datasource
+        implements cache_data_source_versionable {
+    /** @var array Data in cache */
+    protected $data = [];
+
+    /** @var cache_phpunit_dummy_datasource_versionable Last created instance */
+    protected static $lastinstance;
+
+    /**
+     * Returns an instance of this object for use with the cache.
+     *
+     * @param cache_definition $definition
+     * @return cache_phpunit_dummy_datasource New object
+     */
+    public static function get_instance_for_cache(cache_definition $definition):
+            cache_phpunit_dummy_datasource_versionable {
+        self::$lastinstance = new cache_phpunit_dummy_datasource_versionable();
+        return self::$lastinstance;
+    }
+
+    /**
+     * Gets the last instance that was created.
+     *
+     * @return cache_phpunit_dummy_datasource_versionable
+     */
+    public static function get_last_instance(): cache_phpunit_dummy_datasource_versionable {
+        return self::$lastinstance;
+    }
+
+    /**
+     * Sets up the datasource so that it has a value for a particular key.
+     *
+     * @param string $key Key
+     * @param int $version Version for key
+     * @param mixed $data
+     */
+    public function has_value(string $key, int $version, $data): void {
+        $this->data[$key] = new \core_cache\version_wrapper($data, $version);
+    }
+
+    /**
+     * Loads versioned data.
+     *
+     * @param int|string $key Key
+     * @param int $requiredversion Minimum version number
+     * @param mixed $actualversion Should be set to the actual version number retrieved
+     * @return mixed Data retrieved from cache or false if none
+     */
+    public function load_for_cache_versioned($key, int $requiredversion, &$actualversion) {
+        if (!array_key_exists($key, $this->data)) {
+            return false;
+        }
+        $value = $this->data[$key];
+        if ($value->version < $requiredversion) {
+            return false;
+        }
+        $actualversion = $value->version;
+        return $value->data;
+    }
+}
+

cache/tests/fixtures/cachestore_file_with_ttl_wrappers.php

@@ -0,0 +1,37 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * A subclass of cachestore_file but which doesn't report that it has TTL support.
+ *
+ * This is so we can easily test behaviour involving the TTL wrapper objects.
+ *
+ * @package core_cache
+ * @copyright 2021 The Open University
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cachestore_file_with_ttl_wrappers extends cachestore_file {
+    /**
+     * Reports the same supported features as the parent, but without SUPPORTS_NATIVE_TTL.
+     *
+     * @param array $configuration Configuration
+     * @return int Supported features
+     */
+    public static function get_supported_features(array $configuration = array()) {
+        return parent::get_supported_features($configuration) - self::SUPPORTS_NATIVE_TTL;
+    }
+}
+

cache/tests/fixtures/lib.php

@@ -0,0 +1,600 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Support library for the cache PHPUnit tests.
+ *
+ * This file is part of Moodle's cache API, affectionately called MUC.
+ * It contains the components that are requried in order to use caching.
+ *
+ * @package    core
+ * @category   cache
+ * @copyright  2012 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+require_once($CFG->dirroot.'/cache/locallib.php');
+
+/**
+ * Override the default cache configuration for our own maniacal purposes.
+ *
+ * This class was originally named cache_config_phpunittest but was renamed in 2.9
+ * because it is used for both unit tests and acceptance tests.
+ *
+ * @since 2.9
+ * @copyright 2012 Sam Hemelryk
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cache_config_testing extends cache_config_writer {
+
+    /**
+     * Creates the default configuration and saves it.
+     *
+     * This function calls config_save, however it is safe to continue using it afterwards as this function should only ever
+     * be called when there is no configuration file already.
+     *
+     * @param bool $forcesave If set to true then we will forcefully save the default configuration file.
+     * @return true|array Returns true if the default configuration was successfully created.
+     *     Returns a configuration array if it could not be saved. This is a bad situation. Check your error logs.
+     */
+    public static function create_default_configuration($forcesave = false) {
+        global $CFG;
+        // HACK ALERT.
+        // We probably need to come up with a better way to create the default stores, or at least ensure 100% that the
+        // default store plugins are protected from deletion.
+        $writer = new self;
+        $writer->configstores = self::get_default_stores();
+        $writer->configdefinitions = self::locate_definitions();
+        $defaultapplication = 'default_application';
+
+        $appdefine = defined('TEST_CACHE_USING_APPLICATION_STORE') ? TEST_CACHE_USING_APPLICATION_STORE : false;
+        if ($appdefine !== false && preg_match('/^[a-zA-Z][a-zA-Z0-9_]+$/', $appdefine)) {
+            $expectedstore = $appdefine;
+            $file = $CFG->dirroot.'/cache/stores/'.$appdefine.'/lib.php';
+            $class = 'cachestore_'.$appdefine;
+            if (file_exists($file)) {
+                require_once($file);
+            }
+            if (class_exists($class) && $class::ready_to_be_used_for_testing()) {
+                /* @var cache_store $class */
+                $writer->configstores['test_application'] = array(
+                    'name' => 'test_application',
+                    'plugin' => $expectedstore,
+                    'modes' => $class::get_supported_modes(),
+                    'features' => $class::get_supported_features(),
+                    'configuration' => $class::unit_test_configuration()
+                );
+
+                $defaultapplication = 'test_application';
+            }
+        }
+
+        $writer->configmodemappings = array(
+            array(
+                'mode' => cache_store::MODE_APPLICATION,
+                'store' => $defaultapplication,
+                'sort' => -1
+            ),
+            array(
+                'mode' => cache_store::MODE_SESSION,
+                'store' => 'default_session',
+                'sort' => -1
+            ),
+            array(
+                'mode' => cache_store::MODE_REQUEST,
+                'store' => 'default_request',
+                'sort' => -1
+            )
+        );
+        $writer->configlocks = array(
+            'default_file_lock' => array(
+                'name' => 'cachelock_file_default',
+                'type' => 'cachelock_file',
+                'dir' => 'filelocks',
+                'default' => true
+            )
+        );
+
+        $factory = cache_factory::instance();
+        // We expect the cache to be initialising presently. If its not then something has gone wrong and likely
+        // we are now in a loop.
+        if (!$forcesave && $factory->get_state() !== cache_factory::STATE_INITIALISING) {
+            return $writer->generate_configuration_array();
+        }
+        $factory->set_state(cache_factory::STATE_SAVING);
+        $writer->config_save();
+        return true;
+    }
+
+    /**
+     * Returns the expected path to the configuration file.
+     *
+     * We override this function to add handling for $CFG->altcacheconfigpath.
+     * We want to support it so that people can run unit tests against alternative cache setups.
+     * However we don't want to ever make changes to the file at $CFG->altcacheconfigpath so we
+     * always use dataroot and copy the alt file there as required.
+     *
+     * @throws cache_exception
+     * @return string The absolute path
+     */
+    protected static function get_config_file_path() {
+        global $CFG;
+        // We always use this path.
+        $configpath = $CFG->dataroot.'/muc/config.php';
+
+        if (!empty($CFG->altcacheconfigpath)) {
+
+            // No need to check we are within a test here, this is the cache config class that gets used
+            // only when one of those is true.
+            if  (!defined('TEST_CACHE_USING_ALT_CACHE_CONFIG_PATH') || !TEST_CACHE_USING_ALT_CACHE_CONFIG_PATH) {
+                // TEST_CACHE_USING_ALT_CACHE_CONFIG_PATH has not being defined or is false, we want to use the default.
+                return $configpath;
+            }
+
+            $path = $CFG->altcacheconfigpath;
+            if (is_dir($path) && is_writable($path)) {
+                // Its a writable directory, thats fine. Convert it to a file.
+                $path = $CFG->altcacheconfigpath.'/cacheconfig.php';
+            }
+            if (is_readable($path)) {
+                $directory = dirname($configpath);
+                if ($directory !== $CFG->dataroot && !file_exists($directory)) {
+                    $result = make_writable_directory($directory, false);
+                    if (!$result) {
+                        throw new cache_exception('ex_configcannotsave', 'cache', '', null, 'Cannot create config directory. Check the permissions on your moodledata directory.');
+                    }
+                }
+                // We don't care that this fails but we should let the developer know.
+                if (!is_readable($configpath) && !@copy($path, $configpath)) {
+                    debugging('Failed to copy alt cache config file to required location');
+                }
+            }
+        }
+
+        // We always use the dataroot location.
+        return $configpath;
+    }
+
+    /**
+     * Adds a definition to the stack
+     * @param string $area
+     * @param array $properties
+     * @param bool $addmapping By default this method adds a definition and a mapping for that definition. You can
+     *    however set this to false if you only want it to add the definition and not the mapping.
+     */
+    public function phpunit_add_definition($area, array $properties, $addmapping = true) {
+        if (!array_key_exists('overrideclass', $properties)) {
+            switch ($properties['mode']) {
+                case cache_store::MODE_APPLICATION:
+                    $properties['overrideclass'] = 'cache_phpunit_application';
+                    break;
+                case cache_store::MODE_SESSION:
+                    $properties['overrideclass'] = 'cache_phpunit_session';
+                    break;
+                case cache_store::MODE_REQUEST:
+                    $properties['overrideclass'] = 'cache_phpunit_request';
+                    break;
+            }
+        }
+        $this->configdefinitions[$area] = $properties;
+        if ($addmapping) {
+            switch ($properties['mode']) {
+                case cache_store::MODE_APPLICATION:
+                    $this->phpunit_add_definition_mapping($area, 'default_application', 0);
+                    break;
+                case cache_store::MODE_SESSION:
+                    $this->phpunit_add_definition_mapping($area, 'default_session', 0);
+                    break;
+                case cache_store::MODE_REQUEST:
+                    $this->phpunit_add_definition_mapping($area, 'default_request', 0);
+                    break;
+            }
+        }
+    }
+
+    /**
+     * Removes a definition.
+     * @param string $name
+     */
+    public function phpunit_remove_definition($name) {
+        unset($this->configdefinitions[$name]);
+    }
+
+    /**
+     * Removes the configured stores so that there are none available.
+     */
+    public function phpunit_remove_stores() {
+        $this->configstores = array();
+    }
+
+    /**
+     * Forcefully adds a file store.
+     *
+     * You can turn off native TTL support if you want a way to test TTL wrapper objects.
+     *
+     * @param string $name
+     * @param bool $nativettl If false, uses fixture that turns off native TTL support
+     */
+    public function phpunit_add_file_store(string $name, bool $nativettl = true): void {
+        if (!$nativettl) {
+            require_once(__DIR__ . '/cachestore_file_with_ttl_wrappers.php');
+        }
+        $this->configstores[$name] = array(
+            'name' => $name,
+            'plugin' => 'file',
+            'configuration' => array(
+                'path' => ''
+            ),
+            'features' => 6,
+            'modes' => 3,
+            'mappingsonly' => false,
+            'class' => $nativettl ? 'cachestore_file' : 'cachestore_file_with_ttl_wrappers',
+            'default' => false,
+            'lock' => 'cachelock_file_default'
+        );
+    }
+
+    /**
+     * Hacks the in-memory configuration for a store.
+     *
+     * @param string $store Name of store to edit e.g. 'default_application'
+     * @param array $configchanges List of config changes
+     */
+    public function phpunit_edit_store_config(string $store, array $configchanges): void {
+        foreach ($configchanges as $name => $value) {
+            $this->configstores[$store]['configuration'][$name] = $value;
+        }
+    }
+
+    /**
+     * Forcefully adds a session store.
+     *
+     * @param string $name
+     */
+    public function phpunit_add_session_store($name) {
+        $this->configstores[$name] = array(
+            'name' => $name,
+            'plugin' => 'session',
+            'configuration' => array(),
+            'features' => 14,
+            'modes' => 2,
+            'default' => true,
+            'class' => 'cachestore_session',
+            'lock' => 'cachelock_file_default',
+        );
+    }
+
+    /**
+     * Forcefully injects a definition => store mapping.
+     *
+     * This function does no validation, you should only be calling if it you know
+     * exactly what to expect.
+     *
+     * @param string $definition
+     * @param string $store
+     * @param int $sort
+     */
+    public function phpunit_add_definition_mapping($definition, $store, $sort) {
+        $this->configdefinitionmappings[] = array(
+            'store' => $store,
+            'definition' => $definition,
+            'sort' => (int)$sort
+        );
+    }
+
+    /**
+     * Overrides the default site identifier used by the Cache API so that we can be sure of what it is.
+     *
+     * @return string
+     */
+    public function get_site_identifier() {
+        global $CFG;
+        return $CFG->wwwroot.'phpunit';
+    }
+
+    /**
+     * Checks if the configuration file exists.
+     *
+     * @return bool True if it exists
+     */
+    public static function config_file_exists() {
+        // Allow for late static binding by using static.
+        $configfilepath = static::get_config_file_path();
+
+        // Invalidate opcode php cache, so we get correct status of file.
+        core_component::invalidate_opcode_php_cache($configfilepath);
+        return file_exists($configfilepath);
+    }
+}
+
+
+/**
+ * Dummy object for testing cacheable object interface and interaction
+ *
+ * Wake from cache needs specific testing at times to ensure that during multiple
+ * cache get() requests it's possible to verify that it's getting woken each time.
+ *
+ * @copyright  2012 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cache_phpunit_dummy_object extends stdClass implements cacheable_object {
+    /**
+     * Test property 1
+     * @var string
+     */
+    public $property1;
+    /**
+     * Test property 1
+     * @var string
+     */
+    public $property2;
+    /**
+     * Test property time for verifying wake is run at each get() call.
+     * @var float
+     */
+    public $propertytime;
+    /**
+     * Constructor
+     * @param string $property1
+     * @param string $property2
+     */
+    public function __construct($property1, $property2, $propertytime = null) {
+        $this->property1 = $property1;
+        $this->property2 = $property2;
+        $this->propertytime = $propertytime === null ? microtime(true) : $propertytime;
+    }
+    /**
+     * Prepares this object for caching
+     * @return array
+     */
+    public function prepare_to_cache() {
+        return array($this->property1.'_ptc', $this->property2.'_ptc', $this->propertytime);
+    }
+    /**
+     * Returns this object from the cache
+     * @param array $data
+     * @return cache_phpunit_dummy_object
+     */
+    public static function wake_from_cache($data) {
+        $time = null;
+        if (!is_null($data[2])) {
+            // Windows 32bit microtime() resolution is 15ms, we ensure the time has moved forward.
+            do {
+                $time = microtime(true);
+            } while ($time == $data[2]);
+
+        }
+        return new cache_phpunit_dummy_object(array_shift($data).'_wfc', array_shift($data).'_wfc', $time);
+    }
+}
+
+/**
+ * Dummy data source object for testing data source interface and implementation
+ *
+ * @copyright  2012 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cache_phpunit_dummy_datasource implements cache_data_source {
+    /**
+     * Returns an instance of this object for use with the cache.
+     *
+     * @param cache_definition $definition
+     * @return cache_phpunit_dummy_datasource
+     */
+    public static function get_instance_for_cache(cache_definition $definition) {
+        return new cache_phpunit_dummy_datasource();
+    }
+
+    /**
+     * Loads a key for the cache.
+     *
+     * @param string $key
+     * @return string
+     */
+    public function load_for_cache($key) {
+        return $key.' has no value really.';
+    }
+
+    /**
+     * Loads many keys for the cache
+     *
+     * @param array $keys
+     * @return array
+     */
+    public function load_many_for_cache(array $keys) {
+        $return = array();
+        foreach ($keys as $key) {
+            $return[$key] = $key.' has no value really.';
+        }
+        return $return;
+    }
+}
+
+/**
+ * PHPUnit application cache loader.
+ *
+ * Used to expose things we could not otherwise see within an application cache.
+ *
+ * @copyright  2012 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cache_phpunit_application extends cache_application {
+
+    /**
+     * Returns the class of the store immediately associated with this cache.
+     * @return string
+     */
+    public function phpunit_get_store_class() {
+        return get_class($this->get_store());
+    }
+
+    /**
+     * Returns all the interfaces the cache store implements.
+     * @return array
+     */
+    public function phpunit_get_store_implements() {
+        return class_implements($this->get_store());
+    }
+
+    /**
+     * Returns the given key directly from the static acceleration array.
+     *
+     * @param string $key
+     * @return false|mixed
+     */
+    public function phpunit_static_acceleration_get($key) {
+        return $this->static_acceleration_get($key);
+    }
+
+    /**
+     * Purges only the static acceleration while leaving the rest of the store in tack.
+     *
+     * Used for behaving like you have loaded 2 pages, and reset static while the backing store
+     * still contains all the same data.
+     *
+     */
+    public function phpunit_static_acceleration_purge() {
+        $this->static_acceleration_purge();
+    }
+}
+
+/**
+ * PHPUnit session cache loader.
+ *
+ * Used to expose things we could not otherwise see within an session cache.
+ *
+ * @copyright  2012 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cache_phpunit_session extends cache_session {
+
+    /** @var Static member used for emulating the behaviour of session_id() during the tests. */
+    protected static $sessionidmockup = 'phpunitmockupsessionid';
+
+    /**
+     * Returns the class of the store immediately associated with this cache.
+     * @return string
+     */
+    public function phpunit_get_store_class() {
+        return get_class($this->get_store());
+    }
+
+    /**
+     * Returns all the interfaces the cache store implements.
+     * @return array
+     */
+    public function phpunit_get_store_implements() {
+        return class_implements($this->get_store());
+    }
+
+    /**
+     * Provide access to the {@link cache_session::get_key_prefix()} method.
+     *
+     * @return string
+     */
+    public function phpunit_get_key_prefix() {
+        return $this->get_key_prefix();
+    }
+
+    /**
+     * Allows to inject the session identifier.
+     *
+     * @param string $sessionid
+     */
+    public static function phpunit_mockup_session_id($sessionid) {
+        static::$sessionidmockup = $sessionid;
+    }
+
+    /**
+     * Override the parent behaviour so that it does not need the actual session_id() call.
+     */
+    protected function set_session_id() {
+        $this->sessionid = static::$sessionidmockup;
+    }
+}
+
+/**
+ * PHPUnit request cache loader.
+ *
+ * Used to expose things we could not otherwise see within an request cache.
+ *
+ * @copyright  2012 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cache_phpunit_request extends cache_request {
+
+    /**
+     * Returns the class of the store immediately associated with this cache.
+     * @return string
+     */
+    public function phpunit_get_store_class() {
+        return get_class($this->get_store());
+    }
+
+    /**
+     * Returns all the interfaces the cache store implements.
+     * @return array
+     */
+    public function phpunit_get_store_implements() {
+        return class_implements($this->get_store());
+    }
+}
+
+/**
+ * Dummy overridden cache loader class that we can use to test overriding loader functionality.
+ *
+ * @copyright  2012 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cache_phpunit_dummy_overrideclass extends cache_application {
+    // Satisfying the code pre-checker is just part of my day job.
+}
+
+/**
+ * Cache PHPUnit specific factory.
+ *
+ * @copyright  2012 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cache_phpunit_factory extends cache_factory {
+    /**
+     * Exposes the cache_factory's disable method.
+     *
+     * Perhaps one day that method will be made public, for the time being it is protected.
+     */
+    public static function phpunit_disable() {
+        parent::disable();
+    }
+}
+
+/**
+ * Cache PHPUnit specific Cache helper.
+ *
+ * @copyright  2018 Andrew Nicols <andrew@nicols.co.uk>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class cache_phpunit_cache extends cache {
+    /**
+     * Make the changes which simulate a new request within the cache.
+     * This essentially resets currently held static values in the class, and increments the current timestamp.
+     */
+    public static function simulate_new_request() {
+        self::$now += 0.1;
+        self::$purgetoken = null;
+    }
+}

cache/tests/fixtures/stores.php

@@ -0,0 +1,193 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Cache store test fixtures.
+ *
+ * @package    core
+ * @category   cache
+ * @copyright  2013 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * An abstract class to make writing unit tests for cache stores very easy.
+ *
+ * @package    core
+ * @category   cache
+ * @copyright  2013 Sam Hemelryk
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+abstract class cachestore_tests extends advanced_testcase {
+
+    /**
+     * Returns the class name for the store.
+     *
+     * @return string
+     */
+    abstract protected function get_class_name();
+
+    /**
+     * Sets up the fixture, for example, open a network connection.
+     * This method is called before a test is executed.
+     */
+    public function setUp(): void {
+        $class = $this->get_class_name();
+        if (!class_exists($class) || !$class::are_requirements_met()) {
+            $this->markTestSkipped('Could not test '.$class.'. Requirements are not met.');
+        }
+        parent::setUp();
+    }
+    /**
+     * Run the unit tests for the store.
+     */
+    public function test_test_instance() {
+        $class = $this->get_class_name();
+
+        $modes = $class::get_supported_modes();
+        if ($modes & cache_store::MODE_APPLICATION) {
+            $definition = cache_definition::load_adhoc(cache_store::MODE_APPLICATION, $class, 'phpunit_test');
+            $instance = new $class($class.'_test', $class::unit_test_configuration());
+
+            if (!$instance->is_ready()) {
+                $this->markTestSkipped('Could not test '.$class.'. No test instance configured for application caches.');
+            } else {
+                $instance->initialise($definition);
+                $this->run_tests($instance);
+            }
+        }
+        if ($modes & cache_store::MODE_SESSION) {
+            $definition = cache_definition::load_adhoc(cache_store::MODE_SESSION, $class, 'phpunit_test');
+            $instance = new $class($class.'_test', $class::unit_test_configuration());
+
+            if (!$instance->is_ready()) {
+                $this->markTestSkipped('Could not test '.$class.'. No test instance configured for session caches.');
+            } else {
+                $instance->initialise($definition);
+                $this->run_tests($instance);
+            }
+        }
+        if ($modes & cache_store::MODE_REQUEST) {
+            $definition = cache_definition::load_adhoc(cache_store::MODE_REQUEST, $class, 'phpunit_test');
+            $instance = new $class($class.'_test', $class::unit_test_configuration());
+
+            if (!$instance->is_ready()) {
+                $this->markTestSkipped('Could not test '.$class.'. No test instance configured for request caches.');
+            } else {
+                $instance->initialise($definition);
+                $this->run_tests($instance);
+            }
+        }
+    }
+
+    /**
+     * Test the store for basic functionality.
+     */
+    public function run_tests(cache_store $instance) {
+        $object = new stdClass;
+        $object->data = 1;
+
+        // Test set with a string.
+        $this->assertTrue($instance->set('test1', 'test1'));
+        $this->assertTrue($instance->set('test2', 'test2'));
+        $this->assertTrue($instance->set('test3', '3'));
+        $this->assertTrue($instance->set('other3', '3'));
+
+        // Test get with a string.
+        $this->assertSame('test1', $instance->get('test1'));
+        $this->assertSame('test2', $instance->get('test2'));
+        $this->assertSame('3', $instance->get('test3'));
+
+        // Test find and find with prefix if this class implements the searchable interface.
+        if ($instance->is_searchable()) {
+            // Extra settings here ignore the return order of the array.
+            $this->assertEqualsCanonicalizing(['test3', 'test1', 'test2', 'other3'], $instance->find_all());
+
+            // Extra settings here ignore the return order of the array.
+            $this->assertEqualsCanonicalizing(['test2', 'test1', 'test3'], $instance->find_by_prefix('test'));
+            $this->assertEquals(['test2'], $instance->find_by_prefix('test2'));
+            $this->assertEquals(['other3'], $instance->find_by_prefix('other'));
+            $this->assertEquals([], $instance->find_by_prefix('nothere'));
+        }
+
+        // Test set with an int.
+        $this->assertTrue($instance->set('test1', 1));
+        $this->assertTrue($instance->set('test2', 2));
+
+        // Test get with an int.
+        $this->assertSame(1, $instance->get('test1'));
+        $this->assertIsInt($instance->get('test1'));
+        $this->assertSame(2, $instance->get('test2'));
+        $this->assertIsInt($instance->get('test2'));
+
+        // Test set with a bool.
+        $this->assertTrue($instance->set('test1', true));
+
+        // Test get with an bool.
+        $this->assertSame(true, $instance->get('test1'));
+        $this->assertIsBool($instance->get('test1'));
+
+        // Test with an object.
+        $this->assertTrue($instance->set('obj', $object));
+        if ($instance::get_supported_features() & cache_store::DEREFERENCES_OBJECTS) {
+            $this->assertNotSame($object, $instance->get('obj'), 'Objects must be dereferenced when returned.');
+        }
+        $this->assertEquals($object, $instance->get('obj'));
+
+        // Test delete.
+        $this->assertTrue($instance->delete('test1'));
+        $this->assertTrue($instance->delete('test3'));
+        $this->assertFalse($instance->delete('test3'));
+        $this->assertFalse($instance->get('test1'));
+        $this->assertSame(2, $instance->get('test2'));
+        $this->assertTrue($instance->set('test1', 'test1'));
+
+        // Test purge.
+        $this->assertTrue($instance->purge());
+        $this->assertFalse($instance->get('test1'));
+        $this->assertFalse($instance->get('test2'));
+
+        // Test set_many.
+        $outcome = $instance->set_many(array(
+            array('key' => 'many1', 'value' => 'many1'),
+            array('key' => 'many2', 'value' => 'many2'),
+            array('key' => 'many3', 'value' => 'many3'),
+            array('key' => 'many4', 'value' => 'many4'),
+            array('key' => 'many5', 'value' => 'many5')
+        ));
+        $this->assertSame(5, $outcome);
+        $this->assertSame('many1', $instance->get('many1'));
+        $this->assertSame('many5', $instance->get('many5'));
+        $this->assertFalse($instance->get('many6'));
+
+        // Test get_many.
+        $result = $instance->get_many(array('many1', 'many3', 'many5', 'many6'));
+        $this->assertIsArray($result);
+        $this->assertCount(4, $result);
+        $this->assertSame(array(
+            'many1' => 'many1',
+            'many3' => 'many3',
+            'many5' => 'many5',
+            'many6' => false,
+        ), $result);
+
+        // Test delete_many.
+        $this->assertSame(3, $instance->delete_many(array('many2', 'many3', 'many4')));
+        $this->assertSame(2, $instance->delete_many(array('many1', 'many5', 'many6')));
+    }
+}

cache/tests/store_test.php

@@ -0,0 +1,79 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace core_cache;
+
+/**
+ * Unit tests for cache_store functionality.
+ *
+ * @package core_cache
+ * @copyright 2021 The Open University
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class store_test extends \advanced_testcase {
+
+    /**
+     * Tests the default implementation of cache_size_details, which does some
+     * complicated statistics.
+     */
+    public function test_cache_size_details(): void {
+        // Fill a store with 100 entries of varying size.
+        $store = self::create_static_store();
+        for ($i = 0; $i < 100; $i++) {
+            $store->set('key' . $i, str_repeat('x', $i));
+        }
+
+        // Do the statistics for 10 random picks.
+        $details = $store->cache_size_details(10);
+        $this->assertTrue($details->supported);
+        $this->assertEquals(100, $details->items);
+
+        // Min/max possible means if it picks the smallest/largest 10.
+        $this->assertGreaterThan(22, $details->mean);
+        $this->assertLessThan(115, $details->mean);
+        // Min/max possible SD.
+        $this->assertLessThan(49, $details->sd);
+        $this->assertGreaterThan(2.8, $details->sd);
+        // Lowest possible confidence margin is about 1.74.
+        $this->assertGreaterThan(1.7, $details->margin);
+
+        // Repeat the statistics for a pick of all 100 entries (exact).
+        $details = $store->cache_size_details(100);
+        $this->assertTrue($details->supported);
+        $this->assertEquals(100, $details->items);
+        $this->assertEqualsWithDelta(69.3, $details->mean, 0.1);
+        $this->assertEqualsWithDelta(29.2, $details->sd, 0.1);
+        $this->assertEquals(0, $details->margin);
+    }
+
+    /**
+     * Creates a static store for testing.
+     *
+     * @return \cachestore_static Store
+     */
+    protected static function create_static_store(): \cachestore_static {
+        require_once(__DIR__ . '/../stores/static/lib.php');
+        $store = new \cachestore_static('frog');
+        $definition = \cache_definition::load('zombie', [
+                'mode' => \cache_store::MODE_REQUEST,
+                'component' => 'phpunit',
+                'area' => 'store_test',
+                'simplekeys' => true
+        ]);
+        $store->initialise($definition);
+        return $store;
+    }
+}