diff --git a/privacy/classes/tests/request/content_writer.php b/privacy/classes/tests/request/content_writer.php
index 5ae8a2868cd..78c1c62624a 100644
--- a/privacy/classes/tests/request/content_writer.php
+++ b/privacy/classes/tests/request/content_writer.php
@@ -141,13 +141,17 @@ class content_writer implements \core_privacy\local\request\content_writer {
      * @param   \stdClass       $data       The data to be exported
      */
     public function export_data(array $subcontext, \stdClass $data) : \core_privacy\local\request\content_writer {
-        array_push($subcontext, 'data');
-
-        $finalcontent = $data;
+        $finalcontent = [
+            'children' => [],
+            'data' => $data,
+        ];
 
         while ($pathtail = array_pop($subcontext)) {
             $finalcontent = [
-                $pathtail => $finalcontent,
+                'children' => [
+                    $pathtail => $finalcontent,
+                ],
+                'data' => [],
             ];
         }
 
@@ -165,10 +169,8 @@ class content_writer implements \core_privacy\local\request\content_writer {
     public function get_data(array $subcontext = []) {
         $basepath = $this->data[$this->context->id];
         while ($subpath = array_shift($subcontext)) {
-            if (isset($basepath[$subpath])) {
-                $basepath = $basepath[$subpath];
-            } else {
-                return [];
+            if (isset($basepath['children']) && isset($basepath['children'][$subpath])) {
+                $basepath = $basepath['children'][$subpath];
             }
         }
 
@@ -195,18 +197,22 @@ class content_writer implements \core_privacy\local\request\content_writer {
         $value,
         string $description
     ) : \core_privacy\local\request\content_writer {
-        array_push($subcontext, 'metadata');
-
         $finalcontent = [
-            $key => (object) [
-                'value' => $value,
-                'description' => $description,
+            'children' => [],
+            'metadata' => [
+                $key => (object) [
+                    'value' => $value,
+                    'description' => $description,
+                ],
             ],
         ];
 
         while ($pathtail = array_pop($subcontext)) {
             $finalcontent = [
-                $pathtail => $finalcontent,
+                'children' => [
+                    $pathtail => $finalcontent,
+                ],
+                'metadata' => [],
             ];
         }
 
@@ -224,8 +230,8 @@ class content_writer implements \core_privacy\local\request\content_writer {
     public function get_all_metadata(array $subcontext = []) {
         $basepath = $this->metadata[$this->context->id];
         while ($subpath = array_shift($subcontext)) {
-            if (isset($basepath[$subpath])) {
-                $basepath = $basepath[$subpath];
+            if (isset($basepath['children']) && isset($basepath['children'][$subpath])) {
+                $basepath = $basepath['children'][$subpath];
             }
         }
 
@@ -245,13 +251,14 @@ class content_writer implements \core_privacy\local\request\content_writer {
      * @return  array                       The metadata as a series of keys to value + descrition objects.
      */
     public function get_metadata(array $subcontext = [], $key, $valueonly = true) {
-        $data = $this->get_all_metadata($subcontext);
+        $keys = $this->get_all_metadata($subcontext);
 
-        if (!isset($data[$key])) {
+        if (isset($keys[$key])) {
+            $metadata = $keys[$key];
+        } else {
             return null;
         }
 
-        $metadata = $data[$key];
         if ($valueonly) {
             return $metadata->value;
         } else {
@@ -267,14 +274,19 @@ class content_writer implements \core_privacy\local\request\content_writer {
      * @param   \stdClass       $data       The related data to export.
      */
     public function export_related_data(array $subcontext, $name, $data) : \core_privacy\local\request\content_writer {
-        array_push($subcontext, $name);
-        array_push($subcontext, 'data');
-
-        $finalcontent = $data;
+        $finalcontent = [
+            'children' => [],
+            'data' => [
+                $name => $data,
+            ],
+        ];
 
         while ($pathtail = array_pop($subcontext)) {
             $finalcontent = [
-                $pathtail => $finalcontent,
+                'children' => [
+                    $pathtail => $finalcontent,
+                ],
+                'data' => [],
             ];
         }
 
@@ -290,22 +302,27 @@ class content_writer implements \core_privacy\local\request\content_writer {
      * @param   string          $filename   The name of the intended filename.
      * @return  array                       The metadata as a series of keys to value + descrition objects.
      */
-    public function get_related_data(array $subcontext = [], $filename) {
+    public function get_related_data(array $subcontext = [], $filename = null) {
         $basepath = $this->relateddata[$this->context->id];
-        $subcontext[] = $filename;
         while ($subpath = array_shift($subcontext)) {
-            if (isset($basepath[$subpath])) {
-                $basepath = $basepath[$subpath];
-            } else {
-                return [];
+            if (isset($basepath['children']) && isset($basepath['children'][$subpath])) {
+                $basepath = $basepath['children'][$subpath];
             }
         }
 
         if (isset($basepath['data'])) {
-            return $basepath['data'];
-        } else {
-            return [];
+            $data = $basepath['data'];
+            if (null !== $filename) {
+                if (isset($data[$filename])) {
+                    return $data[$filename];
+                }
+                return null;
+            }
+
+            return $data;
         }
+
+        return null;
     }
 
     /**
@@ -319,11 +336,17 @@ class content_writer implements \core_privacy\local\request\content_writer {
         $filename = clean_param($filename, PARAM_FILE);
 
         $finalcontent = [
-            $filename => $filecontent,
+            'children' => [],
+            'files' => [
+                $filename => $filecontent,
+            ],
         ];
         while ($pathtail = array_pop($subcontext)) {
             $finalcontent = [
-                $pathtail => $finalcontent,
+                'children' => [
+                    $pathtail => $finalcontent,
+                ],
+                'files' => [],
             ];
         }
 
@@ -340,18 +363,23 @@ class content_writer implements \core_privacy\local\request\content_writer {
      * @return  string                      The content of the file.
      */
     public function get_custom_file(array $subcontext = [], $filename = null) {
-        if (!empty($filename)) {
-            array_push($subcontext, $filename);
-        }
-
         $basepath = $this->customfiles[$this->context->id];
         while ($subpath = array_shift($subcontext)) {
-            if (isset($basepath[$subpath])) {
-                $basepath = $basepath[$subpath];
+            if (isset($basepath['children']) && isset($basepath['children'][$subpath])) {
+                $basepath = $basepath['children'][$subpath];
             }
         }
 
-        return $basepath;
+        if (isset($basepath['files'])) {
+            if (null !== $filename) {
+                if (isset($basepath['files'][$filename])) {
+                    return $basepath['files'][$filename];
+                }
+                return null;
+            }
+            return $basepath['files'];
+        }
+        return null;
     }
 
     /**
@@ -394,18 +422,24 @@ class content_writer implements \core_privacy\local\request\content_writer {
      */
     public function export_file(array $subcontext, \stored_file $file) : \core_privacy\local\request\content_writer  {
         if (!$file->is_directory()) {
-            $subcontextextra = [
-                'files',
-                $file->get_filepath(),
-            ];
-            $newsubcontext = array_merge($subcontext, $subcontextextra);
+            $filepath = explode(DIRECTORY_SEPARATOR, $file->get_filepath());
+            $filepath[] = $file->get_filename();
+            $filepath = array_filter($filepath);
+            $filepath = implode('/', $filepath);
 
             $finalcontent = [
-                $file,
+                'children' => [],
+                'files' => [
+                    $filepath => $file,
+                ],
             ];
+
             while ($pathtail = array_pop($subcontext)) {
                 $finalcontent = [
-                    $pathtail => $finalcontent,
+                    'children' => [
+                        $pathtail => $finalcontent,
+                    ],
+                    'files' => [],
                 ];
             }
 
@@ -424,12 +458,16 @@ class content_writer implements \core_privacy\local\request\content_writer {
     public function get_files(array $subcontext = []) {
         $basepath = $this->files[$this->context->id];
         while ($subpath = array_shift($subcontext)) {
-            if (isset($basepath[$subpath])) {
-                $basepath = $basepath[$subpath];
+            if (isset($basepath['children']) && isset($basepath['children'][$subpath])) {
+                $basepath = $basepath['children'][$subpath];
             }
         }
 
-        return $basepath;
+        if (isset($basepath['files'])) {
+            return $basepath['files'];
+        }
+
+        return [];
     }
 
     /**
diff --git a/privacy/tests/tests_content_writer_test.php b/privacy/tests/tests_content_writer_test.php
new file mode 100644
index 00000000000..1f815c11434
--- /dev/null
+++ b/privacy/tests/tests_content_writer_test.php
@@ -0,0 +1,361 @@
+<?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/>.
+
+/**
+ * Unit Tests for the Content Writer used for unit testing.
+ *
+ * @package     core_privacy
+ * @category    test
+ * @copyright   2018 Andrew Nicols <andrew@nicols.co.uk>
+ * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+global $CFG;
+
+use \core_privacy\local\request\writer;
+use \core_privacy\tests\request\content_writer;
+
+/**
+ * Unit Tests for the Content Writer used for unit testing.
+ *
+ * @copyright   2018 Andrew Nicols <andrew@nicols.co.uk>
+ * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class tests_content_writer_test extends advanced_testcase {
+
+    /**
+     * It should be possible to store and retrieve data.
+     */
+    public function test_export_data() {
+        $context = \context_system::instance();
+        $writer = $this->get_writer_instance();
+
+        $dataa = (object) [
+            'example' => 'a',
+        ];
+        $datab = (object) [
+            'example' => 'b',
+        ];
+
+        $writer->set_context($context)
+            ->export_data(['data'], $dataa)
+            ->export_data([], $datab);
+
+        $data = $writer->get_data([]);
+        $this->assertSame($datab, $data);
+
+        $data = $writer->get_data(['data']);
+        $this->assertSame($dataa, $data);
+    }
+
+    /**
+     * It should be possible to store and retrieve data at the same point in different contexts.
+     */
+    public function test_export_data_no_context_clash() {
+        $writer = $this->get_writer_instance();
+
+        $context = \context_system::instance();
+        $dataa = (object) [
+            'example' => 'a',
+        ];
+        $writer->set_context($context)
+            ->export_data(['data'], $dataa);
+
+        $adminuser = \core_user::get_user_by_username('admin');
+        $usercontext = \context_user::instance($adminuser->id);
+        $datab = (object) [
+            'example' => 'b',
+        ];
+        $writer->set_context($usercontext)
+            ->export_data(['data'], $datab);
+
+        $writer->set_context($context);
+        $data = $writer->get_data(['data']);
+        $this->assertSame($dataa, $data);
+
+        $writer->set_context($usercontext);
+        $data = $writer->get_data(['data']);
+        $this->assertSame($datab, $data);
+    }
+
+    /**
+     * It should be possible to store and retrieve metadata.
+     */
+    public function test_export_metadata() {
+        $context = \context_system::instance();
+        $writer = $this->get_writer_instance();
+
+        $writer->set_context($context)
+            ->export_metadata(['metadata'], 'somekey', 'value1', 'description1')
+            ->export_metadata([], 'somekey', 'value2', 'description2');
+
+        $allmetadata = $writer->get_all_metadata([]);
+        $this->assertCount(1, $allmetadata);
+        $this->assertArrayHasKey('somekey', $allmetadata);
+        $this->assertEquals('value2', $allmetadata['somekey']->value);
+        $this->assertEquals('description2', $allmetadata['somekey']->description);
+
+        $metadata = $writer->get_metadata([], 'somekey', false);
+        $this->assertEquals('value2', $metadata->value);
+        $this->assertEquals('description2', $metadata->description);
+        $this->assertEquals('value2', $writer->get_metadata([], 'somekey', true));
+
+        $allmetadata = $writer->get_all_metadata(['metadata']);
+        $this->assertCount(1, $allmetadata);
+        $this->assertArrayHasKey('somekey', $allmetadata);
+        $this->assertEquals('value1', $allmetadata['somekey']->value);
+        $this->assertEquals('description1', $allmetadata['somekey']->description);
+
+        $metadata = $writer->get_metadata(['metadata'], 'somekey', false);
+        $this->assertEquals('value1', $metadata->value);
+        $this->assertEquals('description1', $metadata->description);
+        $this->assertEquals('value1', $writer->get_metadata(['metadata'], 'somekey', true));
+    }
+
+    /**
+     * It should be possible to store and retrieve metadata at the same point in different contexts.
+     */
+    public function test_export_metadata_no_context_clash() {
+        $writer = $this->get_writer_instance();
+
+        $context = \context_system::instance();
+        $writer->set_context($context)
+            ->export_metadata(['metadata'], 'somekey', 'value1', 'description1');
+
+        $adminuser = \core_user::get_user_by_username('admin');
+        $usercontext = \context_user::instance($adminuser->id);
+        $writer->set_context($usercontext)
+            ->export_metadata(['metadata'], 'somekey', 'value2', 'description2');
+
+        $writer->set_context($context);
+        $allmetadata = $writer->get_all_metadata(['metadata']);
+        $this->assertCount(1, $allmetadata);
+        $this->assertArrayHasKey('somekey', $allmetadata);
+        $this->assertEquals('value1', $allmetadata['somekey']->value);
+        $this->assertEquals('description1', $allmetadata['somekey']->description);
+
+        $metadata = $writer->get_metadata(['metadata'], 'somekey', false);
+        $this->assertEquals('value1', $metadata->value);
+        $this->assertEquals('description1', $metadata->description);
+        $this->assertEquals('value1', $writer->get_metadata(['metadata'], 'somekey', true));
+
+        $writer->set_context($usercontext);
+        $allmetadata = $writer->get_all_metadata(['metadata']);
+        $this->assertCount(1, $allmetadata);
+        $this->assertArrayHasKey('somekey', $allmetadata);
+        $this->assertEquals('value2', $allmetadata['somekey']->value);
+        $this->assertEquals('description2', $allmetadata['somekey']->description);
+
+        $metadata = $writer->get_metadata(['metadata'], 'somekey', false);
+        $this->assertEquals('value2', $metadata->value);
+        $this->assertEquals('description2', $metadata->description);
+        $this->assertEquals('value2', $writer->get_metadata(['metadata'], 'somekey', true));
+    }
+
+    /**
+     * It should be possible to export files in the files and children contexts.
+     */
+    public function test_export_file_special_folders() {
+        $context = \context_system::instance();
+
+        $filea = $this->get_stored_file('/', 'files');
+        $fileb = $this->get_stored_file('/children/', 'foo.zip');
+
+        $writer = $this->get_writer_instance()
+            ->set_context($context)
+            ->export_file([], $filea)
+            ->export_file([], $fileb);
+
+        $files = $writer->get_files([]);
+
+        $this->assertCount(2, $files);
+        $this->assertEquals($filea, $files['files']);
+        $this->assertEquals($fileb, $files['children/foo.zip']);
+    }
+
+    /**
+     * It should be possible to export mutliple files in the same subcontext/path space but different context and not
+     * have them clash.
+     */
+    public function test_export_file_no_context_clash() {
+        $writer = $this->get_writer_instance();
+        $context = \context_system::instance();
+        $filea = $this->get_stored_file('/foo/', 'foo.txt');
+        $writer = $this->get_writer_instance()
+            ->set_context($context)
+            ->export_file([], $filea);
+
+        $adminuser = \core_user::get_user_by_username('admin');
+        $usercontext = \context_user::instance($adminuser->id);
+        $fileb = $this->get_stored_file('/foo/', 'foo.txt');
+        $writer->set_context($usercontext)
+            ->export_file([], $fileb);
+
+        $writer->set_context($context);
+        $files = $writer->get_files([]);
+        $this->assertCount(1, $files);
+        $this->assertEquals($filea, $files['foo/foo.txt']);
+
+        $writer->set_context($usercontext);
+        $files = $writer->get_files([]);
+        $this->assertCount(1, $files);
+        $this->assertEquals($fileb, $files['foo/foo.txt']);
+    }
+
+    /**
+     * It should be possible to export related data in the files and children contexts.
+     */
+    public function test_export_related_data() {
+        $context = \context_system::instance();
+
+        $writer = $this->get_writer_instance()
+            ->set_context($context)
+            ->export_related_data(['file', 'data'], 'file', 'data1')
+            ->export_related_data([], 'file', 'data2');
+
+        $data = $writer->get_related_data([]);
+        $this->assertCount(1, $data);
+        $this->assertEquals('data2', $data['file']);
+
+        $data = $writer->get_related_data([], 'file');
+        $this->assertEquals('data2', $data);
+
+        $data = $writer->get_related_data(['file', 'data']);
+        $this->assertCount(1, $data);
+        $this->assertEquals('data1', $data['file']);
+
+        $data = $writer->get_related_data(['file', 'data'], 'file');
+        $this->assertEquals('data1', $data);
+    }
+
+    /**
+     * It should be possible to export related data in the same location,but in a different context.
+     */
+    public function test_export_related_data_no_context_clash() {
+        $writer = $this->get_writer_instance();
+
+        $context = \context_system::instance();
+        $writer->set_context($context)
+            ->export_related_data(['file', 'data'], 'file', 'data1');
+
+        $adminuser = \core_user::get_user_by_username('admin');
+        $usercontext = \context_user::instance($adminuser->id);
+        $writer->set_context($usercontext)
+            ->export_related_data(['file', 'data'], 'file', 'data2');
+
+        $writer->set_context($context);
+        $data = $writer->get_related_data(['file', 'data']);
+        $this->assertCount(1, $data);
+        $this->assertEquals('data1', $data['file']);
+
+        $writer->set_context($usercontext);
+        $data = $writer->get_related_data(['file', 'data']);
+        $this->assertCount(1, $data);
+        $this->assertEquals('data2', $data['file']);
+    }
+
+    /**
+     * It should be possible to export related files in the files and children contexts.
+     */
+    public function test_export_custom_file() {
+        $context = \context_system::instance();
+
+        $writer = $this->get_writer_instance()
+            ->set_context($context)
+            ->export_custom_file(['file.txt'], 'file.txt', 'Content 1')
+            ->export_custom_file([], 'file.txt', 'Content 2');
+
+        $files = $writer->get_custom_file([]);
+        $this->assertCount(1, $files);
+        $this->assertEquals('Content 2', $files['file.txt']);
+        $file = $writer->get_custom_file([], 'file.txt');
+        $this->assertEquals('Content 2', $file);
+
+        $files = $writer->get_custom_file(['file.txt']);
+        $this->assertCount(1, $files);
+        $this->assertEquals('Content 1', $files['file.txt']);
+        $file = $writer->get_custom_file(['file.txt'], 'file.txt');
+        $this->assertEquals('Content 1', $file);
+    }
+
+    /**
+     * It should be possible to export related files in the same location
+     * in different contexts.
+     */
+    public function test_export_custom_file_no_context_clash() {
+        $writer = $this->get_writer_instance();
+        $context = \context_system::instance();
+
+        $writer->set_context($context)
+            ->export_custom_file(['file.txt'], 'file.txt', 'Content 1');
+
+        $adminuser = \core_user::get_user_by_username('admin');
+        $usercontext = \context_user::instance($adminuser->id);
+        $writer->set_context($usercontext)
+            ->export_custom_file(['file.txt'], 'file.txt', 'Content 2');
+
+        $writer->set_context($context);
+        $files = $writer->get_custom_file(['file.txt']);
+        $this->assertCount(1, $files);
+        $this->assertEquals('Content 1', $files['file.txt']);
+
+        $writer->set_context($usercontext);
+        $files = $writer->get_custom_file(['file.txt']);
+        $this->assertCount(1, $files);
+        $this->assertEquals('Content 2', $files['file.txt']);
+    }
+
+    /**
+     * Get a fresh content writer.
+     *
+     * @return  moodle_content_writer
+     */
+    public function get_writer_instance() {
+        $factory = $this->createMock(writer::class);
+        return new content_writer($factory);
+    }
+
+    /**
+     * Helper to create a stored file objectw with the given supplied content.
+     *
+     * @param   string  $filepath The file path to use in the stored_file
+     * @param   string  $filename The file name to use in the stored_file
+     * @return  stored_file
+     */
+    protected function get_stored_file($filepath, $filename) {
+        static $counter = 0;
+        $counter++;
+        $filecontent = "Example content {$counter}";
+        $contenthash = file_storage::hash_from_string($filecontent);
+
+        $file = $this->getMockBuilder(stored_file::class)
+            ->setMethods(null)
+            ->setConstructorArgs([
+                get_file_storage(),
+                (object) [
+                    'contenthash' => $contenthash,
+                    'filesize' => strlen($filecontent),
+                    'filepath' => $filepath,
+                    'filename' => $filename,
+                ]
+            ])
+            ->getMock();
+
+        return $file;
+    }
+}