added test to client

test/client_test.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require_relative "test_helper"
+
+class ClientTest < Minitest::Test
+  include HTTPX
+
+  def test_client_request
+    client1 = Client.new
+    client2 = Client.new(headers: {"accept" => "text/css"})
+
+    request1 = client1.request(:get, "http://google.com", headers: {"accept" => "text/html"})
+    assert request1.headers["accept"] == "text/html", "header hasn't been properly set"
+
+    request2 = client2.request(:get, "http://google.com")
+    assert request2.headers["accept"] == "text/css", "header hasn't been properly set"
+    
+    request3 = client2.request(:get, "http://google.com", headers: {"accept" => "text/javascript"})
+    assert request3.headers["accept"] == "text/javascript", "header hasn't been properly set"
+  end
+end