PHPUnit (truncated...) - SOLUTION
If you experienced the difficult task to debug the (truncated…) error message through PhpUnit see below global solution ! The exception caught is related to the guzzle version A try-catch around your phpunit test would get the GuzzleException $e Example $client = new GuzzleHttp\Client([‘base_uri’ => ‘ https://foo.com/api/ ']); try { $response = $client->request('GET','/v1/testYourEndpoint'); } catch (\GuzzleHttp\Exception\ClientErrorResponseException $e) { var_dump($e->getResponse()->getBody()->getContents()); } catch (\GuzzleHttp\Exception\RequestException $e) { var_dump($e->getResponse()->getBody()->getContents()); } catch (\GuzzleHttp\Exception\ClientException $e) { var_dump($e->getResponse()->getBody()->getContents()); } try { $response = $client -> request ( 'GET' , '/v1/testYourEndpoint' ); } catch ( \GuzzleHttp\Exception\ClientErrorResponseException $e ) { ...