Require psr/http-client-implementation

Author: bezin

composer.json

@@ -22,13 +22,15 @@
         "psr/log": "~1.0|~2.0|~3.0",
         "php-http/httplug": "^2.3",
         "nyholm/psr7": "^1.5",
-        "php-http/discovery": "^1.14"
+        "php-http/discovery": "^1.14",
+        "psr/http-client-implementation": "*"
     },
     "require-dev": {
         "phpunit/phpunit": "~9.3.0",
         "monolog/monolog": "1.*|2.*",
         "phpstan/phpstan": "^0.12.81",
-        "friendsofphp/php-cs-fixer": "^3.5"
+        "friendsofphp/php-cs-fixer": "^3.5",
+        "php-http/mock-client": "^1.5"
     },
     "suggest": {
         "monolog/monolog": "Allows to handle logs",