diff --git a/lib/classes/oauth2/discovery/auth_server_config_reader.php b/lib/classes/oauth2/discovery/auth_server_config_reader.php
new file mode 100644
index 00000000000..ed7c58350ea
--- /dev/null
+++ b/lib/classes/oauth2/discovery/auth_server_config_reader.php
@@ -0,0 +1,109 @@
+<?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\oauth2\discovery;
+
+use core\http_client;
+use GuzzleHttp\Exception\ClientException;
+
+/**
+ * Simple reader class, allowing OAuth 2 Authorization Server Metadata to be read from an auth server's well-known.
+ *
+ * {@link https://www.rfc-editor.org/rfc/rfc8414}
+ *
+ * @package    core
+ * @copyright  2023 Jake Dallimore <jrhdallimore@gmail.com>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class auth_server_config_reader {
+
+    /** @var \stdClass the config object read from the discovery document. */
+    protected \stdClass $metadata;
+
+    /** @var \moodle_url the base URL for the auth server which was last used during a read.*/
+    protected \moodle_url $issuerurl;
+
+    /**
+     * Constructor.
+     *
+     * @param http_client $httpclient an http client instance.
+     * @param string $wellknownsuffix the well-known suffix, defaulting to 'oauth-authorization-server'.
+     */
+    public function __construct(protected http_client $httpclient,
+        protected string $wellknownsuffix = 'oauth-authorization-server') {
+    }
+
+    /**
+     * Read the metadata from the remote host.
+     *
+     * @param \moodle_url $issuerurl the auth server issuer URL.
+     * @return \stdClass the configuration data object.
+     * @throws ClientException|\GuzzleHttp\Exception\GuzzleException if the http client experiences any problems.
+     */
+    public function read_configuration(\moodle_url $issuerurl): \stdClass {
+        $this->issuerurl = $issuerurl;
+        $this->validate_uri();
+
+        $url = $this->get_configuration_url()->out(false);
+        $response = $this->httpclient->request('GET', $url);
+        $this->metadata = json_decode($response->getBody());
+        return $this->metadata;
+    }
+
+    /**
+     * Make sure the base URI is suitable for use in discovery.
+     *
+     * @return void
+     * @throws \moodle_exception if the URI fails validation.
+     */
+    protected function validate_uri() {
+        if (!empty($this->issuerurl->get_query_string())) {
+            throw new \moodle_exception('Error: '.__METHOD__.': Auth server base URL cannot contain a query component.');
+        }
+        if (strtolower($this->issuerurl->get_scheme()) !== 'https') {
+            throw new \moodle_exception('Error: '.__METHOD__.': Auth server base URL must use HTTPS scheme.');
+        }
+        // This catches URL fragments. Since a query string is ruled out above, out_omit_querystring(false) returns only fragments.
+        if ($this->issuerurl->out_omit_querystring() != $this->issuerurl->out(false)) {
+            throw new \moodle_exception('Error: '.__METHOD__.': Auth server base URL must not contain fragments.');
+        }
+    }
+
+    /**
+     * Get the Auth server metadata URL.
+     *
+     * Per {@link https://www.rfc-editor.org/rfc/rfc8414#section-3}, if the issuer URL contains a path component,
+     * the well known suffix is added between the host and path components.
+     *
+     * @return \moodle_url the full URL to the auth server metadata.
+     */
+    protected function get_configuration_url(): \moodle_url {
+        $path = $this->issuerurl->get_path();
+        if (!empty($path) && $path !== '/') {
+            // Insert the well known suffix between the host and path components.
+            $port = $this->issuerurl->get_port() ? ':'.$this->issuerurl->get_port() : '';
+            $uri = $this->issuerurl->get_scheme() . "://" . $this->issuerurl->get_host() . $port ."/".
+                ".well-known/" . $this->wellknownsuffix . $path;
+        } else {
+            // No path, just append the well known suffix.
+            $uri = $this->issuerurl->out(false);
+            $uri .= (substr($uri, -1) == '/' ? '' : '/');
+            $uri .= ".well-known/$this->wellknownsuffix";
+        }
+
+        return new \moodle_url($uri);
+    }
+}
diff --git a/lib/tests/oauth2/discovery/auth_server_config_reader_test.php b/lib/tests/oauth2/discovery/auth_server_config_reader_test.php
new file mode 100644
index 00000000000..fb5671b8870
--- /dev/null
+++ b/lib/tests/oauth2/discovery/auth_server_config_reader_test.php
@@ -0,0 +1,674 @@
+<?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\oauth2\discovery;
+
+use core\http_client;
+use GuzzleHttp\Exception\ClientException;
+use GuzzleHttp\Handler\MockHandler;
+use GuzzleHttp\HandlerStack;
+use GuzzleHttp\Middleware;
+use GuzzleHttp\Psr7\Response;
+use Psr\Http\Message\ResponseInterface;
+
+/**
+ * Unit tests for {@see auth_server_config_reader}.
+ *
+ * @coversDefaultClass \core\oauth2\discovery\auth_server_config_reader
+ * @package core
+ * @copyright 2023 Jake Dallimore <jrhdallimore@gmail.com>
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class auth_server_config_reader_test extends \advanced_testcase {
+
+    /**
+     * Test reading the config for an auth server.
+     *
+     * @covers ::read_configuration
+     * @dataProvider config_provider
+     * @param string $issuerurl the auth server issuer URL.
+     * @param ResponseInterface $httpresponse a stub HTTP response.
+     * @param null|string $altwellknownsuffix an alternate value for the well known suffix to use in the reader.
+     * @param array $expected test expectations.
+     * @return void
+     */
+    public function test_read_configuration(string $issuerurl, ResponseInterface $httpresponse, ?string $altwellknownsuffix = null,
+            array $expected = []) {
+
+        $mock = new MockHandler([$httpresponse]);
+        $handlerstack = HandlerStack::create($mock);
+        if (!empty($expected['request'])) {
+            // Request history tracking to allow asserting that request was sent as expected below (to the stub client).
+            $container = [];
+            $history = Middleware::history($container);
+            $handlerstack->push($history);
+        }
+
+        $args = [
+            new http_client(['handler' => $handlerstack]),
+        ];
+        if (!is_null($altwellknownsuffix)) {
+            $args[] = $altwellknownsuffix;
+        }
+
+        if (!empty($expected['exception'])) {
+            $this->expectException($expected['exception']);
+        }
+        $configreader = new auth_server_config_reader(...$args);
+        $config = $configreader->read_configuration(new \moodle_url($issuerurl));
+
+        if (!empty($expected['request'])) {
+            // Verify the request goes to the correct URL (i.e. the well known suffix is correctly positioned).
+            $this->assertEquals($expected['request']['url'], $container[0]['request']->getUri());
+        }
+
+        $this->assertEquals($expected['metadata'], (array) $config);
+    }
+
+    /**
+     * Provider for testing read_configuration().
+     *
+     * @return array test data.
+     */
+    public function config_provider(): array {
+        return [
+            'Valid, good issuer URL, good config' => [
+                'issuer_url' => 'https://app.example.com',
+                'http_response' => new Response(
+                    200,
+                    ['Content-Type' => 'application/json'],
+                    json_encode([
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ])
+                ),
+                'well_known_suffix' => null,
+                'expected' => [
+                    'request' => [
+                        'url' => 'https://app.example.com/.well-known/oauth-authorization-server'
+                    ],
+                    'metadata' => [
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ]
+                ]
+            ],
+            'Valid, issuer URL with path component confirming well known suffix placement' => [
+                'issuer_url' => 'https://app.example.com/some/path',
+                'http_response' => new Response(
+                    200,
+                    ['Content-Type' => 'application/json'],
+                    json_encode([
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ])
+                ),
+                'well_known_suffix' => null,
+                'expected' => [
+                    'request' => [
+                        'url' => 'https://app.example.com/.well-known/oauth-authorization-server/some/path'
+                    ],
+                    'metadata' => [
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ]
+                ]
+            ],
+            'Valid, single trailing / path only' => [
+                'issuer_url' => 'https://app.example.com/',
+                'http_response' => new Response(
+                    200,
+                    ['Content-Type' => 'application/json'],
+                    json_encode([
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ])
+                ),
+                'well_known_suffix' => null,
+                'expected' => [
+                    'request' => [
+                        'url' => 'https://app.example.com/.well-known/oauth-authorization-server'
+                    ],
+                    'metadata' => [
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ]
+                ]
+            ],
+            'Invalid, non HTTPS issuer URL' => [
+                'issuer_url' => 'http://app.example.com',
+                'http_response' => new Response(
+                    200,
+                    ['Content-Type' => 'application/json'],
+                    json_encode([
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ])
+                ),
+                'well_known_suffix' => null,
+                'expected' => [
+                    'exception' => \moodle_exception::class
+                ]
+            ],
+            'Invalid, query string in issuer URL' => [
+                'issuer_url' => 'https://app.example.com?test=cat',
+                'http_response' => new Response(
+                    200,
+                    ['Content-Type' => 'application/json'],
+                    json_encode([
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ])
+                ),
+                'well_known_suffix' => null,
+                'expected' => [
+                    'exception' => \moodle_exception::class
+                ]
+            ],
+            'Invalid, fragment in issuer URL' => [
+                'issuer_url' => 'https://app.example.com/#cat',
+                'http_response' => new Response(
+                    200,
+                    ['Content-Type' => 'application/json'],
+                    json_encode([
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ])
+                ),
+                'well_known_suffix' => null,
+                'expected' => [
+                    'exception' => \moodle_exception::class
+                ]
+            ],
+            'Valid, port in issuer URL' => [
+                'issuer_url' => 'https://app.example.com:8080/some/path',
+                'http_response' => new Response(
+                    200,
+                    ['Content-Type' => 'application/json'],
+                    json_encode([
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ])
+                ),
+                'well_known_suffix' => null,
+                'expected' => [
+                    'request' => [
+                        'url' => 'https://app.example.com:8080/.well-known/oauth-authorization-server/some/path'
+                    ],
+                    'metadata' => [
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ]
+                ]
+            ],
+            'Valid, alternate well known suffix, no path' => [
+                'issuer_url' => 'https://app.example.com',
+                'http_response' => new Response(
+                    200,
+                    ['Content-Type' => 'application/json'],
+                    json_encode([
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ])
+                ),
+                'well_known_suffix' => 'openid-configuration', // An application using the openid well known, which is valid.
+                'expected' => [
+                    'request' => [
+                        'url' => 'https://app.example.com/.well-known/openid-configuration'
+                    ],
+                    'metadata' => [
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ]
+                ]
+            ],
+            'Valid, alternate well known suffix, with path' => [
+                'issuer_url' => 'https://app.example.com/some/path/',
+                'http_response' => new Response(
+                    200,
+                    ['Content-Type' => 'application/json'],
+                    json_encode([
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ])
+                ),
+                'well_known_suffix' => 'openid-configuration', // An application using the openid well known, which is valid.
+                'expected' => [
+                    'request' => [
+                        'url' => 'https://app.example.com/.well-known/openid-configuration/some/path/'
+                    ],
+                    'metadata' => [
+                        "issuer" => "https://app.example.com",
+                        "authorization_endpoint" => "https://app.example.com/authorize",
+                        "token_endpoint" => "https://app.example.com/token",
+                        "token_endpoint_auth_methods_supported" => [
+                            "client_secret_basic",
+                            "private_key_jwt"
+                        ],
+                        "token_endpoint_auth_signing_alg_values_supported" => [
+                            "RS256",
+                            "ES256"
+                        ],
+                        "userinfo_endpoint" => "https://app.example.com/userinfo",
+                        "jwks_uri" => "https://app.example.com/jwks.json",
+                        "registration_endpoint" => "https://app.example.com/register",
+                        "scopes_supported" => [
+                            "openid",
+                            "profile",
+                            "email",
+                        ],
+                        "response_types_supported" => [
+                            "code",
+                            "code token"
+                        ],
+                        "service_documentation" => "http://app.example.com/service_documentation.html",
+                        "ui_locales_supported" => [
+                            "en-US",
+                            "en-GB",
+                            "fr-FR",
+                        ]
+                    ]
+                ]
+            ],
+            'Invalid, bad response' => [
+                'issuer_url' => 'https://app.example.com',
+                'http_response' => new Response(404),
+                'well_known_suffix' => null,
+                'expected' => [
+                    'exception' => ClientException::class
+                ]
+            ]
+        ];
+    }
+}