Use library DSL in RBS tests

Replace custom NetHTTPTestSigHelper/NetHTTPRBSTestCase with the
standard RBS::UnitTest library DSL, which validates that manifest.yaml
declares all required dependencies.

Author: sferik

test_sig/test_helper.rb

@@ -1,48 +1,4 @@
-require "pathname"
 require "test/unit"
 require "rbs"
 require "rbs/test"
 require "rbs/unit_test"
-
-module NetHTTPTestSigHelper
-  extend self
-
-  LOCAL_SIG_DIR = Pathname(__dir__).join("..", "sig").expand_path
-  SUPPORT_LIBRARIES = %w[
-    cgi
-    net-protocol
-    open-uri
-    openssl
-    resolv
-    securerandom
-    socket
-    strscan
-    tempfile
-    timeout
-    uri
-    zlib
-  ].freeze
-
-  def env
-    @env ||= begin
-      loader = RBS::EnvironmentLoader.new
-      loader.add(path: LOCAL_SIG_DIR)
-      SUPPORT_LIBRARIES.each do |library|
-        loader.add(library: library, version: nil)
-      end
-      RBS::Environment.from_loader(loader).resolve_type_names
-    end
-  end
-end
-
-class NetHTTPRBSTestCase < Test::Unit::TestCase
-  include RBS::UnitTest::TypeAssertions
-
-  def self.env
-    NetHTTPTestSigHelper.env
-  end
-
-  def self.builder
-    @builder ||= RBS::DefinitionBuilder.new(env: env)
-  end
-end

test_sig/test_net_http.rb

@@ -55,9 +55,11 @@ def with_server(host)
   end
 end
 
-class NetSingletonTest < NetHTTPRBSTestCase
+class NetSingletonTest < Test::Unit::TestCase
+  include RBS::UnitTest::TypeAssertions
   include WithServer
 
+  library "net-http"
   testing "singleton(::Net::HTTP)"
 
   def test_get
@@ -125,9 +127,11 @@ def test_start
    end
 end
 
-class NetInstanceTest < NetHTTPRBSTestCase
+class NetInstanceTest < Test::Unit::TestCase
+  include RBS::UnitTest::TypeAssertions
   include WithServer
 
+  library "net-http"
   testing "::Net::HTTP"
 
   class TestNet < Net::HTTP
@@ -397,9 +401,11 @@ def test_request
   end
 end
 
-class TestHTTPRequest < NetHTTPRBSTestCase
+class TestHTTPRequest < Test::Unit::TestCase
+  include RBS::UnitTest::TypeAssertions
   include WithServer
 
+  library "net-http"
   testing "::Net::HTTPRequest"
 
   def test_inspect
@@ -544,7 +550,10 @@ def test_iteration_on_headers
   end
 end
 
-class TestSingletonNetHTTPResponse < NetHTTPRBSTestCase
+class TestSingletonNetHTTPResponse < Test::Unit::TestCase
+  include RBS::UnitTest::TypeAssertions
+
+  library "net-http"
   testing "singleton(::Net::HTTPResponse)"
 
   def test_body_permitted_?
@@ -553,9 +562,11 @@ def test_body_permitted_?
   end
 end
 
-class TestInstanceNetHTTPResponse < NetHTTPRBSTestCase
+class TestInstanceNetHTTPResponse < Test::Unit::TestCase
+  include RBS::UnitTest::TypeAssertions
   include WithServer
 
+  library "net-http"
   testing "::Net::HTTPResponse"
 
   class Foo