diff --git a/lib/rbs/cli.rb b/lib/rbs/cli.rb
index bf3a3c22a..5f0413490 100644
--- a/lib/rbs/cli.rb
+++ b/lib/rbs/cli.rb
@@ -1061,7 +1061,7 @@ def run_test(args, options)
       env_hash = {
         'RUBYOPT' => "#{ENV['RUBYOPT']} -rrbs/test/setup",
         'RBS_TEST_OPT' => test_opt(options),
-        'RBS_TEST_LOGLEVEL' => %w(DEBUG INFO WARN ERROR FATAL)[RBS.logger_level || 5] || "UNKNOWN",
+        'RBS_TEST_LOGLEVEL' => RBS.logger_level || "UNKNOWN",
         'RBS_TEST_SAMPLE_SIZE' => sample_size,
         'RBS_TEST_DOUBLE_SUITE' => double_suite,
         'RBS_TEST_UNCHECKED_CLASSES' => (unchecked_classes.join(',') unless unchecked_classes.empty?),
diff --git a/lib/rbs/environment_loader.rb b/lib/rbs/environment_loader.rb
index de3cb8fa0..833a9c893 100644
--- a/lib/rbs/environment_loader.rb
+++ b/lib/rbs/environment_loader.rb
@@ -49,6 +49,14 @@ def add(path: nil, library: nil, version: nil, resolve_dependencies: true)
       case
       when path
         dirs << path
+
+        # search for manifest.yaml
+        if (manifest = path.each_entry.find { |s| s.basename.to_s == "manifest.yaml" })
+          local_lib = RBS::Collection::Sources::Local.new(path: path, base_directory: Pathname.pwd)
+          local_lib.dependencies_of("", "")&.each do |dep|
+            add(library: dep['name'], version: nil)
+          end
+        end
       when library
         if libs.add?(Library.new(name: library, version: version)) && resolve_dependencies
           resolve_dependencies(library: library, version: version)
diff --git a/test/rbs/cli_test.rb b/test/rbs/cli_test.rb
index a9becac11..2e8666398 100644
--- a/test/rbs/cli_test.rb
+++ b/test/rbs/cli_test.rb
@@ -1044,6 +1044,22 @@ def test_prototype__runtime__todo
   def test_test
     Dir.mktmpdir do |dir|
       dir = Pathname(dir)
+      dir.join('foo.rb').write(<<~RB)
+      class Foo
+        def foo(*)
+        end
+      end
+
+      module Bar
+        class Baz
+          def foo
+          end
+        end
+      end
+
+      # violates type definition
+      Foo.new.foo(1)
+      RB
       dir.join('foo.rbs').write(<<~RBS)
         class Foo
           def foo: () -> void
@@ -1059,10 +1075,12 @@ def foo: () -> void
       with_cli do |cli|
         # `exit` is a common shell built-in command.
         assert_rbs_test_no_errors(cli, dir, %w(--target ::Foo exit))
+        assert_rbs_test_no_errors(cli, dir, %w(--target ::Foo exit), %w(--log-level debug))
 
         refute_cli_success cli.run(%w(test))
         refute_cli_success cli.run(%W(-I #{dir} test))
         refute_cli_success cli.run(%W(-I #{dir} test --target ::Foo))
+        refute_cli_success cli.run(%W(-I #{dir} test --target ::Foo ruby #{dir}/foo.rb))
       end
     end
   end
@@ -1715,8 +1733,8 @@ def x: () -> untyped
     end
   end
 
-  def assert_rbs_test_no_errors cli, dir, arg_array
-    args = ['-I', dir.to_s, 'test', *arg_array]
+  def assert_rbs_test_no_errors cli, dir, arg_array, env_array = []
+    args = ['-I', dir.to_s, *env_array, 'test', *arg_array]
     exit_status = cli.run(args)
     assert_instance_of Integer, exit_status
     assert_predicate exit_status, :zero?
diff --git a/test/rbs/environment_loader_test.rb b/test/rbs/environment_loader_test.rb
index 893699000..27100f80a 100644
--- a/test/rbs/environment_loader_test.rb
+++ b/test/rbs/environment_loader_test.rb
@@ -82,6 +82,22 @@ def test_loading_stdlib
     end
   end
 
+    def test_loading_stdlib_via_manifest
+    mktmpdir do |path|
+      path.join("manifest.yaml").write(<<-RBS)
+dependencies:
+ - name: uri
+    RBS
+      loader = EnvironmentLoader.new
+      loader.add(path: path)
+
+      env = Environment.new
+      loader.load(env: env)
+
+      assert_operator env.class_decls, :key?, RBS::TypeName.parse("::URI")
+    end
+  end
+
   def test_loading_library_from_gem_repo
     mktmpdir do |path|
       (path + "gems").mkdir