test: Write test for OpenfeatureAPI to return No-op client when OpenfeatureClient is unresolvable (#157)

### Overview

This pull request refactors the client creation logic in
`OpenFeatureAPI` to improve testability and resilience.

- Introduces a dedicated `resolveClient` method, which encapsulates
client instantiation logic.

- Ensures that failures during client resolution are handled gracefully
by returning a `NoOpClient`.

- Adds a testing dependency to allow mocking of final classes, enabling
comprehensive test coverage without altering production code.

---------

Signed-off-by: tmakinde <[email protected]>

Author: Tmakinde

composer.json

@@ -23,6 +23,7 @@
         "behat/behat": "^3.11",
         "captainhook/captainhook": "^5.10",
         "captainhook/plugin-composer": "^5.3",
+        "dg/bypass-finals": "^1.9",
         "ergebnis/composer-normalize": "^2.25",
         "hamcrest/hamcrest-php": "^2.0",
         "mdwheele/zalgo": "^0.3.1",

src/OpenFeatureAPI.php

@@ -66,6 +66,11 @@ public function getProvider(): Provider
         return $this->provider;
     }
 
+    protected function resolveClient(string $name, string $version): OpenFeatureClient
+    {
+        return new OpenFeatureClient($this, $name, $version);
+    }
+
     /**
      * -----------------
      * Requirement 1.1.2
@@ -103,7 +108,7 @@ public function getClient(?string $name = null, ?string $version = null): Client
         $version = $version ?? 'OpenFeature';
 
         try {
-            $client = new OpenFeatureClient($this, $name, $version);
+            $client = $this->resolveClient($name, $version);
             $client->setLogger($this->getLogger());
 
             return $client;

tests/unit/OpenFeatureAPITest.php

@@ -4,13 +4,16 @@
 
 namespace OpenFeature\Test\unit;
 
+use DG\BypassFinals;
+use Exception;
 use Mockery\MockInterface;
 use OpenFeature\OpenFeatureAPI;
 use OpenFeature\Test\APITestHelper;
 use OpenFeature\Test\TestCase;
 use OpenFeature\Test\TestHook;
 use OpenFeature\Test\TestProvider;
 use OpenFeature\implementation\flags\EvaluationContext;
+use OpenFeature\implementation\flags\NoOpClient;
 use OpenFeature\implementation\provider\NoOpProvider;
 use OpenFeature\interfaces\flags\API;
 use OpenFeature\interfaces\hooks\Hook;
@@ -220,4 +223,23 @@ public function testApiWillCreateClientWithProvider(): void
         $this->assertEquals($name, $client->getMetadata()->getName());
         $this->assertInstanceOf(TestProvider::class, $api->getProvider());
     }
+
+    /**
+     * @runInSeparateProcess
+     * @preserveGlobalState disabled
+     */
+    public function testReturnsNoOpClientWhenClientResolutionFails(): void
+    {
+        BypassFinals::enable();
+        $name = 'test-name';
+        $version = 'test-version';
+        /** @var (MockInterface&OpenFeatureAPI) $api @phpstan-ignore-line */
+        $api = $this->mockery(OpenFeatureAPI::class)->shouldAllowMockingProtectedMethods()->makePartial(); // @phpstan-ignore-line
+
+        $api->shouldReceive('resolveClient')->once()
+            ->with($name, $version)
+            ->andThrow(new Exception('Simulated client resolution failure'));
+        $client = $api->getClient($name, $version);
+        $this->assertInstanceOf(NoOpClient::class, $client);
+    }
 }