diff --git a/exe/rbs b/exe/rbs
index 5bc440ec3e..3366f324fc 100755
--- a/exe/rbs
+++ b/exe/rbs
@@ -4,4 +4,4 @@ $LOAD_PATH << File.join(__dir__, "../lib")
 require "rbs"
 require "rbs/cli"
 
-RBS::CLI.new(stdout: STDOUT, stderr: STDERR).run(ARGV.dup)
+exit RBS::CLI.new(stdout: STDOUT, stderr: STDERR).run(ARGV.dup)
diff --git a/lib/rbs/cli.rb b/lib/rbs/cli.rb
index 2706d86792..c59fe35ea0 100644
--- a/lib/rbs/cli.rb
+++ b/lib/rbs/cli.rb
@@ -136,10 +136,12 @@ def run(args)
       case command
       when :version
         stdout.puts opts.ver
+        0
       when *COMMANDS
         __send__ :"run_#{command}", args, options
       else
         stdout.puts opts.help
+        0
       end
     end
 
@@ -191,6 +193,8 @@ def run_ast(args, options)
 
       stdout.print JSON.generate(decls)
       stdout.flush
+
+      0
     end
 
     def run_list(args, options)
@@ -254,6 +258,8 @@ def run_list(args, options)
           stdout.puts "#{name} (interface)"
         end
       end
+
+      0
     end
 
     def run_ancestors(args, options)
@@ -279,7 +285,7 @@ def run_ancestors(args, options)
 
       unless args.size == 1
         stdout.puts "Expected one argument."
-        return
+        return 1
       end
 
       loader = options.loader()
@@ -317,6 +323,8 @@ def run_ancestors(args, options)
       else
         stdout.puts "Cannot find class: #{type_name}"
       end
+
+      0
     end
 
     def run_methods(args, options)
@@ -344,7 +352,7 @@ def run_methods(args, options)
 
       unless args.size == 1
         stdout.puts "Expected one argument."
-        return
+        return 1
       end
 
       loader = options.loader()
@@ -373,6 +381,8 @@ def run_methods(args, options)
       else
         stdout.puts "Cannot find class: #{type_name}"
       end
+
+      0
     end
 
     def run_method(args, options)
@@ -398,7 +408,7 @@ def run_method(args, options)
 
       unless args.size == 2
         stdout.puts "Expected two arguments, but given #{args.size}."
-        return
+        return 1
       end
 
       loader = options.loader()
@@ -410,7 +420,7 @@ def run_method(args, options)
 
       unless env.module_name?(type_name)
         stdout.puts "Cannot find class: #{type_name}"
-        return
+        return 1
       end
 
       definition = case kind
@@ -426,7 +436,7 @@ def run_method(args, options)
 
       unless method
         stdout.puts "Cannot find method: #{method_name}"
-        return
+        return 1
       end
 
       stdout.puts "#{type_name}#{kind == :instance ? "#" : "."}#{method_name}"
@@ -440,6 +450,8 @@ def run_method(args, options)
         stdout.puts format("    %s %-#{length_max}s   at %s", separator, type, type.location)
         separator = "|"
       end
+
+      0
     end
 
     def run_validate(args, options)
@@ -469,7 +481,7 @@ def run_constant(args, options)
 
       unless args.size == 1
         stdout.puts "Expected one argument."
-        return
+        return 1
       end
 
       loader = options.loader()
@@ -502,6 +514,8 @@ def run_constant(args, options)
       else
         stdout.puts " => [no constant]"
       end
+
+      0
     end
 
     def run_paths(args, options)
@@ -544,6 +558,8 @@ def run_paths(args, options)
           stdout.puts "#{dir} (#{kind_of[dir]}, library, name=#{source.name})"
         end
       end
+
+      0
     end
 
     def run_prototype(args, options)
@@ -647,6 +663,8 @@ def autoload(name, path)
 
         writer = Writer.new(out: stdout)
         writer.write decls
+
+        0
       else
         stdout.puts <<EOU
 Usage: rbs prototype [generator...] [args...]
@@ -660,7 +678,7 @@ def autoload(name, path)
   $ rbs prototype rbi foo.rbi
   $ rbs prototype runtime String
 EOU
-        exit 1
+        1
       end
     end
 
@@ -712,12 +730,12 @@ def run_prototype_file(format, args)
 
       unless has_parser?
         stdout.puts "Not supported on this interpreter (#{RUBY_ENGINE})."
-        exit 1
+        return 1
       end
 
       if args.empty?
         stdout.puts opts
-        return nil
+        return 1
       end
 
       new_parser = -> do
@@ -827,6 +845,8 @@ def run_prototype_file(format, args)
         writer = Writer.new(out: stdout)
         writer.write parser.decls
       end
+
+      0
     end
 
     def run_vendor(args, options)
@@ -880,6 +900,8 @@ def run_vendor(args, options)
 
       stdout.puts "  Copying RBS files..."
       vendorer.copy!
+
+      0
     end
 
     def run_parse(args, options)
@@ -927,7 +949,11 @@ def run_parse(args, options)
         syntax_error = true
       end
 
-      exit 1 if syntax_error
+      if syntax_error
+        1
+      else
+        0
+      end
     end
 
     def run_annotate(args, options)
@@ -975,6 +1001,8 @@ def run_annotate(args, options)
           annotator.annotate_file(path, preserve: preserve)
         end
       end
+
+      0
     end
 
     def test_opt options
@@ -1028,7 +1056,7 @@ def run_test(args, options)
 
       if args.length.zero?
         stdout.puts opts.help
-        exit 1
+        return 1
       end
 
       # @type var env_hash: Hash[String, String?]
@@ -1044,11 +1072,12 @@ def run_test(args, options)
 
       # @type var out: String
       # @type var err: String
+      # @type var status: Process::Status
       out, err, status = __skip__ = Open3.capture3(env_hash, *args)
       stdout.print(out)
       stderr.print(err)
 
-      status
+      status.to_i
     end
 
     def run_collection(args, options)
@@ -1073,7 +1102,7 @@ def run_collection(args, options)
       when 'init'
         if config_path.exist?
           puts "#{config_path} already exists"
-          exit 1
+          return 1
         end
 
         config_path.write(<<~'YAML')
@@ -1101,15 +1130,17 @@ def run_collection(args, options)
       when 'clean'
         unless lock_path.exist?
           puts "#{lock_path} should exist to clean"
-          exit 1
+          return 1
         end
         Collection::Cleaner.new(lockfile_path: lock_path)
       when 'help', 'hel', 'he', 'h'
         puts opts.help
       else
         puts opts.help
-        exit 1
+        return 1
       end
+
+      0
     end
 
     def collection_options(args)
@@ -1171,7 +1202,7 @@ def run_subtract(args, _)
         *minuend_paths, subtrahend_path = args
         unless subtrahend_path
           stdout.puts opts.help
-          exit 1
+          return 1
         end
         subtrahend_paths << subtrahend_path
       else
@@ -1180,7 +1211,7 @@ def run_subtract(args, _)
 
       if minuend_paths.empty?
         stdout.puts opts.help
-        exit 1
+        return 1
       end
 
       subtrahend = Environment.new.tap do |env|
@@ -1213,10 +1244,12 @@ def run_subtract(args, _)
           end
         end
       end
+
+      0
     end
 
     def run_diff(argv, library_options)
-      Diff.new(argv: argv, library_options: library_options, stdout: stdout, stderr: stderr).run
+      Diff.new(stdout: stdout, stderr: stderr).run(argv: argv, library_options: library_options)
     end
   end
 end
diff --git a/lib/rbs/cli/diff.rb b/lib/rbs/cli/diff.rb
index 43c8d4ba6c..f60954b763 100644
--- a/lib/rbs/cli/diff.rb
+++ b/lib/rbs/cli/diff.rb
@@ -3,13 +3,14 @@
 module RBS
   class CLI
     class Diff
-      def initialize(argv:, library_options:, stdout: $stdout, stderr: $stderr)
-        @format = nil
+      def initialize(stdout: $stdout, stderr: $stderr)
         @stdout = stdout
         @stderr = stderr
+      end
 
-        # @type var type_name: String?
-        type_name = nil
+      def run(argv:, library_options:)
+        format = nil #: String?
+        type_name = nil #: String?
         library_options = library_options
         before_path = [] #: Array[String]
         after_path = [] #: Array[String]
@@ -32,7 +33,7 @@ def initialize(argv:, library_options:, stdout: $stdout, stderr: $stderr)
               # Confirmation of methods related to Time class added by including stdlib/time
               $ rbs diff --format diff --type-name Time --after stdlib/time
           HELP
-          o.on("--format NAME")    { |arg| @format = arg }
+          o.on("--format NAME")    { |arg| format = arg }
           o.on("--type-name NAME") { |arg| type_name = arg }
           o.on("--before DIR")     { |arg| before_path << arg }
           o.on("--after DIR")      { |arg| after_path << arg }
@@ -40,28 +41,28 @@ def initialize(argv:, library_options:, stdout: $stdout, stderr: $stderr)
         end
         opt.parse!(argv)
 
-        unless @format && type_name && ["markdown", "diff"].include?(@format)
+        unless format && type_name && ["markdown", "diff"].include?(format)
           @stderr.puts opt.banner
-          exit 1
+          return 1
         end
 
-        @diff = RBS::Diff.new(
+        diff = RBS::Diff.new(
           type_name: TypeName.parse(type_name).absolute!,
           library_options: library_options,
           after_path: after_path,
           before_path: before_path,
           detail: detail,
         )
-      end
 
-      def run
-        public_send("run_#{@format}")
+        public_send("run_#{format}", diff)
+
+        0
       end
 
-      def run_diff
+      def run_diff(diff)
         first = true
         io = RBS::CLI::ColoredIO.new(stdout: @stdout)
-        @diff.each_diff do |before, after|
+        diff.each_diff do |before, after|
           io.puts if !first
           io.puts_red   "- #{before}"
           io.puts_green "+ #{after}"
@@ -69,10 +70,10 @@ def run_diff
         end
       end
 
-      def run_markdown
+      def run_markdown(diff)
         @stdout.puts "| before | after |"
         @stdout.puts "| --- | --- |"
-        @diff.each_diff do |before, after|
+        diff.each_diff do |before, after|
           before.gsub!("|", "\\|")
           after.gsub!("|", "\\|")
           @stdout.puts "| `#{before}` | `#{after}` |"
diff --git a/lib/rbs/cli/validate.rb b/lib/rbs/cli/validate.rb
index d7feb02f8a..7ba52665a9 100644
--- a/lib/rbs/cli/validate.rb
+++ b/lib/rbs/cli/validate.rb
@@ -21,10 +21,18 @@ def add(error)
           finish if @limit == 1
         end
 
+        def try(&block)
+          catch(:finish) do |tag|
+            @tag = tag
+            yield
+            finish()
+          end
+        end
+
         def finish
           if @errors.empty?
             if @exit_error && @has_syntax_error
-              exit 1
+              throw @tag, 1
             else
               # success
             end
@@ -32,8 +40,10 @@ def finish
             @errors.each do |error|
               RBS.logger.error(build_message(error))
             end
-            exit 1
+            throw @tag, 1
           end
+
+          0
         end
 
         private
@@ -81,14 +91,14 @@ def initialize(args:, options:)
       end
 
       def run
-        validate_class_module_definition
-        validate_class_module_alias_definition
-        validate_interface
-        validate_constant
-        validate_global
-        validate_type_alias
-
-        @errors.finish
+        @errors.try do
+          validate_class_module_definition
+          validate_class_module_alias_definition
+          validate_interface
+          validate_constant
+          validate_global
+          validate_type_alias
+        end
       end
 
       private
diff --git a/sig/cli.rbs b/sig/cli.rbs
index d6ce90e2f8..6dcd5bfdfd 100644
--- a/sig/cli.rbs
+++ b/sig/cli.rbs
@@ -46,41 +46,41 @@ module RBS
 
     def has_parser?: () -> bool
 
-    def run: (Array[String] args) -> void
+    def run: (Array[String] args) -> Integer
 
-    def run_ast: (Array[String], LibraryOptions) -> void
+    def run_ast: (Array[String], LibraryOptions) -> Integer
 
-    def run_list: (Array[String], LibraryOptions) -> void
+    def run_list: (Array[String], LibraryOptions) -> Integer
 
-    def run_ancestors: (Array[String], LibraryOptions) -> void
+    def run_ancestors: (Array[String], LibraryOptions) -> Integer
 
-    def run_methods: (Array[String], LibraryOptions) -> void
+    def run_methods: (Array[String], LibraryOptions) -> Integer
 
-    def run_method: (Array[String], LibraryOptions) -> void
+    def run_method: (Array[String], LibraryOptions) -> Integer
 
-    def run_validate: (Array[String], LibraryOptions) -> void
+    def run_validate: (Array[String], LibraryOptions) -> Integer
 
-    def run_constant: (Array[String], LibraryOptions) -> void
+    def run_constant: (Array[String], LibraryOptions) -> Integer
 
-    def run_paths: (Array[String], LibraryOptions) -> void
+    def run_paths: (Array[String], LibraryOptions) -> Integer
 
-    def run_prototype: (Array[String], LibraryOptions) -> void
+    def run_prototype: (Array[String], LibraryOptions) -> Integer
 
-    def run_prototype_file: (String format, Array[String]) -> void
+    def run_prototype_file: (String format, Array[String]) -> Integer
 
-    def run_vendor: (Array[String], LibraryOptions) -> void
+    def run_vendor: (Array[String], LibraryOptions) -> Integer
 
-    def run_parse: (Array[String], LibraryOptions) -> void
+    def run_parse: (Array[String], LibraryOptions) -> Integer
 
-    def run_test: (Array[String], LibraryOptions) -> void
+    def run_test: (Array[String], LibraryOptions) -> Integer
 
-    def run_collection: (Array[String], LibraryOptions) -> void
+    def run_collection: (Array[String], LibraryOptions) -> Integer
 
-    def run_annotate: (Array[String], top) -> void
+    def run_annotate: (Array[String], top) -> Integer
 
-    def run_subtract: (Array[String], top) -> void
+    def run_subtract: (Array[String], top) -> Integer
 
-    def run_diff: (Array[String], LibraryOptions) -> void
+    def run_diff: (Array[String], LibraryOptions) -> Integer
 
     def test_opt: (LibraryOptions) -> String?
 
diff --git a/sig/cli/diff.rbs b/sig/cli/diff.rbs
index a01edbd150..b5a8bb7727 100644
--- a/sig/cli/diff.rbs
+++ b/sig/cli/diff.rbs
@@ -1,21 +1,15 @@
 module RBS
   class CLI
     class Diff
-      @format: String
       @stdout: _IO
       @stderr: _IO
-      @diff: RBS::Diff
 
-      def initialize: (
-        argv: Array[String],
-        library_options: RBS::CLI::LibraryOptions,
-        ?stdout: _IO,
-        ?stderr: _IO,
-      ) -> void
+      def initialize: (?stdout: _IO, ?stderr: _IO) -> void
 
-      def run: () -> void
-      def run_diff: () -> void
-      def run_markdown: () -> void
+      def run: (library_options: RBS::CLI::LibraryOptions, argv: Array[String]) -> Integer
+
+      def run_diff: (RBS::Diff) -> void
+      def run_markdown: (RBS::Diff) -> void
     end
   end
 end
diff --git a/sig/cli/validate.rbs b/sig/cli/validate.rbs
index 65909e73da..790a97c8c9 100644
--- a/sig/cli/validate.rbs
+++ b/sig/cli/validate.rbs
@@ -7,11 +7,20 @@ module RBS
         @has_syntax_error: bool
         @errors: Array[BaseError]
 
+        # The tag that will be thrown in #finish method
+        @tag: top
+
         def initialize: (limit: Integer?, exit_error: boolish) -> void
 
         def add: (BaseError) -> void
 
-        def finish: () -> void
+        # Throws the `@tag` with 0 or 1
+        #
+        # Must be called from the block passed to `#try` method.
+        #
+        def finish: () -> Integer
+
+        def try: () { () -> void } -> Integer
 
         private
 
@@ -25,7 +34,7 @@ module RBS
 
       def initialize: (args: Array[String], options: LibraryOptions) -> void
 
-      def run: () -> void
+      def run: () -> Integer
 
       private
 
diff --git a/test/rbs/cli_test.rb b/test/rbs/cli_test.rb
index 04b5830c06..69cea0a285 100644
--- a/test/rbs/cli_test.rb
+++ b/test/rbs/cli_test.rb
@@ -15,6 +15,18 @@ def stderr
     @stderr ||= StringIO.new
   end
 
+  def assert_cli_success(exit_status = nil, &)
+    exit_status ||= yield
+    assert_instance_of Integer, exit_status
+    assert_predicate exit_status, :zero?, "Expected CLI to succeed, but it failed with status: #{exit_status.inspect}"
+  end
+
+  def refute_cli_success(exit_status = nil, &)
+    exit_status ||= yield
+    assert_instance_of Integer, exit_status
+    assert_predicate exit_status, :nonzero?, "Expected CLI to succeed, but it failed with status: #{exit_status.inspect}"
+  end
+
   # Run `rbs collection` with fresh bundler environment
   #
   # You need this method to test `rbs collection` features.
@@ -52,7 +64,7 @@ def bundle_install(*gems)
     stdout, stderr, status =
       Bundler.with_unbundled_env do
         gems << 'prism' unless gems.include?('prism')
-        
+
         gems = gems.map do |gem|
           if gem == :gemspec
             "gemspec"
@@ -91,7 +103,9 @@ def with_cli
 
   def test_ast
     with_cli do |cli|
-      cli.run(%w(ast))
+      assert_cli_success do
+        cli.run(%w(ast))
+      end
 
       # Outputs a JSON
       JSON.parse stdout.string
@@ -100,7 +114,9 @@ def test_ast
 
   def test_no_stdlib_option
     with_cli do |cli|
-      cli.run(%w(--no-stdlib ast))
+      assert_cli_success do
+        cli.run(%w(--no-stdlib ast))
+      end
 
       assert_equal '[]', stdout.string
     end
@@ -108,28 +124,34 @@ def test_no_stdlib_option
 
   def test_list
     with_cli do |cli|
-      cli.run(%w(-r pathname list))
+      assert_cli_success { cli.run(%w(-r pathname list)) }
       assert_match %r{^::Pathname \(class\)$}, stdout.string
       assert_match %r{^::Kernel \(module\)$}, stdout.string
       assert_match %r{^::_Each \(interface\)$}, stdout.string
     end
 
     with_cli do |cli|
-      cli.run(%w(-r pathname list --class))
+      assert_cli_success do
+        cli.run(%w(-r pathname list --class))
+      end
       assert_match %r{^::Pathname \(class\)$}, stdout.string
       refute_match %r{^::Kernel \(module\)$}, stdout.string
       refute_match %r{^::_Each \(interface\)$}, stdout.string
     end
 
     with_cli do |cli|
-      cli.run(%w(-r pathname list --module))
+      assert_cli_success do
+        cli.run(%w(-r pathname list --module))
+      end
       refute_match %r{^::Pathname \(class\)$}, stdout.string
       assert_match %r{^::Kernel \(module\)$}, stdout.string
       refute_match %r{^::_Each \(interface\)$}, stdout.string
     end
 
     with_cli do |cli|
-      cli.run(%w(-r pathname list --interface))
+      assert_cli_success do
+        cli.run(%w(-r pathname list --interface))
+      end
       refute_match %r{^::Pathname \(class\)$}, stdout.string
       refute_match %r{^::Kernel \(module\)$}, stdout.string
       assert_match %r{^::_Each \(interface\)$}, stdout.string
@@ -145,7 +167,9 @@ module Bar = Kernel
 
       Dir.chdir(dir) do
         with_cli do |cli|
-          cli.run(%w(-I. list))
+          assert_cli_success do
+            cli.run(%w(-I. list))
+          end
 
           assert_match %r{^::Foo \(class alias\)$}, stdout.string
           assert_match %r{^::Bar \(module alias\)$}, stdout.string
@@ -156,7 +180,9 @@ module Bar = Kernel
 
   def test_ancestors
     with_cli do |cli|
-      cli.run(%w(ancestors ::Set))
+      assert_cli_success do
+        cli.run(%w(ancestors ::Set))
+      end
       assert_equal <<-EOF, stdout.string
 ::Set[A]
 ::Enumerable[A]
@@ -167,7 +193,9 @@ def test_ancestors
     end
 
     with_cli do |cli|
-      cli.run(%w(ancestors --instance ::Set))
+      assert_cli_success do
+        cli.run(%w(ancestors --instance ::Set))
+      end
       assert_equal <<-EOF, stdout.string
 ::Set[A]
 ::Enumerable[A]
@@ -178,7 +206,10 @@ def test_ancestors
     end
 
     with_cli do |cli|
-      cli.run(%w(ancestors --singleton ::Set))
+      assert_cli_success do
+        cli.run(%w(ancestors --singleton ::Set))
+      end
+
       assert_equal <<-EOF, stdout.string
 singleton(::Set)
 singleton(::Object)
@@ -202,7 +233,9 @@ class Bar
 
       Dir.chdir(dir) do
         with_cli do |cli|
-          cli.run(%w(-I. ancestors ::Foo))
+          assert_cli_success do
+            cli.run(%w(-I. ancestors ::Foo))
+          end
 
           assert_equal <<~EOF, stdout.string
             ::String
@@ -218,9 +251,9 @@ class Bar
 
   def test_methods
     with_cli do |cli|
-      cli.run(%w(methods ::Set))
-      cli.run(%w(methods --instance ::Set))
-      cli.run(%w(methods --singleton ::Set))
+      assert_cli_success { cli.run(%w(methods ::Set)) }
+      assert_cli_success { cli.run(%w(methods --instance ::Set)) }
+      assert_cli_success { cli.run(%w(methods --singleton ::Set)) }
     end
 
     Dir.mktmpdir do |dir|
@@ -233,12 +266,16 @@ module Bar = Kernel
 
       Dir.chdir(dir) do
         with_cli do |cli|
-          cli.run(%w(-I. methods ::Foo))
+          assert_cli_success do
+            cli.run(%w(-I. methods ::Foo))
+          end
           assert_match %r{^puts \(private\)$}, stdout.string
         end
 
         with_cli do |cli|
-          cli.run(%w(-I. methods --singleton ::Bar))
+          assert_cli_success do
+            cli.run(%w(-I. methods --singleton ::Bar))
+          end
           assert_match %r{^puts \(public\)$}, stdout.string
         end
       end
@@ -247,7 +284,7 @@ module Bar = Kernel
 
   def test_method
     with_cli do |cli|
-      cli.run(%w(method ::Object yield_self))
+      assert_cli_success { cli.run(%w(method ::Object yield_self)) }
       assert_includes stdout.string, '::Object#yield_self'
       assert_includes stdout.string, 'defined_in: ::Kernel'
       assert_includes stdout.string, 'implementation: ::Kernel'
@@ -269,12 +306,12 @@ module Bar = Kernel
 
       Dir.chdir(dir) do
         with_cli do |cli|
-          cli.run(%w(-I. method ::Foo puts))
+          assert_cli_success { cli.run(%w(-I. method ::Foo puts)) }
           assert_match %r{^::Foo#puts$}, stdout.string
         end
 
         with_cli do |cli|
-          cli.run(%w(-I. method --singleton ::Bar puts))
+          assert_cli_success { cli.run(%w(-I. method --singleton ::Bar puts)) }
           assert_match %r{^::Bar\.puts$}, stdout.string
         end
       end
@@ -284,12 +321,12 @@ module Bar = Kernel
 
   def test_validate
     with_cli do |cli|
-      cli.run(%w(--log-level=info validate))
+      assert_cli_success cli.run(%w(--log-level=info validate))
       assert_match(/Validating/, stdout.string)
     end
 
     with_cli do |cli|
-      cli.run(%w(--log-level=warn validate --silent))
+      assert_cli_success cli.run(%w(--log-level=warn validate --silent))
       assert_match(/`--silent` option is deprecated because it's silent by default\. You can use --log-level option of rbs command to display more information\.$/, stdout.string)
     end
   end
@@ -302,7 +339,7 @@ class Hello::World
         end
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
 
@@ -318,7 +355,7 @@ def test_validate_no_type_found_error_2
         Hello::World: Integer
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
 
@@ -334,7 +371,7 @@ def test_validate_no_type_found_error_3
         type Hello::t = Integer
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
 
@@ -355,7 +392,7 @@ module Bar[B]
         end
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
 
@@ -372,7 +409,7 @@ class Foo[A < _Each[B], B < _Foo[A]]
         end
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
 
@@ -395,7 +432,7 @@ class B
           end
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
 
@@ -412,7 +449,7 @@ def test_validate_with_cyclic_type_parameter_bound_3
         end
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
 
@@ -432,7 +469,7 @@ def bar: [X < _Foo[Y], Y < _Bar[Z], Z < _Baz[X]] () -> void
         end
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
 
@@ -473,7 +510,9 @@ module Baz : A, _C
           end
         RBS
 
-        cli.run(["-I", dir, "validate"])
+        assert_cli_success do
+          cli.run(["-I", dir, "validate"])
+        end
       end
     end
   end
@@ -539,8 +578,7 @@ module X7 : A[String, untyped]
           end
         RBS
 
-
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir.to_s, "validate"])
         end
 
@@ -572,7 +610,9 @@ class B[S = self]
           type t[T = self] = untyped
         RBS
 
-        cli.run(["-I", dir, "validate"])
+        assert_cli_success do
+          cli.run(["-I", dir, "validate"])
+        end
 
         assert_include stdout.string, "/a.rbs:1:13...1:17: `self` type is not allowed in this context (RBS::WillSyntaxError)\n"
         assert_include stdout.string, "/a.rbs:4:12...4:16: `self` type is not allowed in this context (RBS::WillSyntaxError)\n"
@@ -598,7 +638,7 @@ class B[A, B = A, C = B?]
           type t[A, B = A, C = B?] = untyped
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
 
@@ -620,7 +660,9 @@ def bar: (void) -> void
           end
         RBS
 
-        cli.run(["-I", dir, "--log-level=warn", "validate"])
+        assert_cli_success do
+          cli.run(["-I", dir, "--log-level=warn", "validate"])
+        end
 
         assert_include stdout.string, "a.rbs:2:11...2:25: `void` type is only allowed in return type or generics parameter (RBS::WillSyntaxError)"
         assert_include stdout.string, "a.rbs:3:11...3:25: `void` type is only allowed in return type or generics parameter (RBS::WillSyntaxError)"
@@ -638,7 +680,9 @@ def bar: (void) -> void
           end
         RBS
 
-        cli.run(["-I", dir, "--log-level=warn", "validate", "--fail-fast"])
+        assert_cli_success do
+          cli.run(["-I", dir, "--log-level=warn", "validate", "--fail-fast"])
+        end
         assert_include stdout.string, "a.rbs:2:11...2:25: `void` type is only allowed in return type or generics parameter (RBS::WillSyntaxError)"
         assert_include stdout.string, "a.rbs:3:11...3:25: `void` type is only allowed in return type or generics parameter (RBS::WillSyntaxError)"
       end
@@ -655,7 +699,7 @@ def bar: (void) -> void
           end
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "--log-level=warn", "validate", "--exit-error-on-syntax-error"])
         end
         assert_include stdout.string, "a.rbs:2:11...2:25: `void` type is only allowed in return type or generics parameter (RBS::WillSyntaxError)"
@@ -674,7 +718,7 @@ def bar: (void) -> void
           end
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "--log-level=warn", "validate", "--fail-fast", "--exit-error-on-syntax-error"])
         end
         assert_include stdout.string, "a.rbs:2:11...2:25: `void` type is only allowed in return type or generics parameter (RBS::WillSyntaxError)"
@@ -685,7 +729,7 @@ def bar: (void) -> void
 
   def test_validate_multiple_with_many_errors
     with_cli do |cli|
-      assert_raise SystemExit do
+      refute_cli_success do
         cli.run(%w(--log-level=warn -I test/multiple_error.rbs validate))
       end
       assert_include(stdout.string, "`void` type is only allowed in return type or generics parameter")
@@ -715,7 +759,7 @@ def test_validate_multiple_with_many_errors
 
   def test_validate_multiple_fail_fast
     with_cli do |cli|
-      assert_raise SystemExit do
+      refute_cli_success do
         cli.run(%w(--log-level=warn -I test/multiple_error.rbs validate --fail-fast))
       end
       assert_include(stdout.string, "test/multiple_error.rbs:2:11...2:25: `void` type is only allowed in return type or generics parameter (RBS::WillSyntaxError)")
@@ -726,7 +770,7 @@ def test_validate_multiple_fail_fast
 
   def test_validate_multiple_fail_fast_and_exit_error_on_syntax_error
     with_cli do |cli|
-      assert_raise SystemExit do
+      refute_cli_success do
         cli.run(%w(--log-level=warn -I test/multiple_error.rbs validate --fail-fast --exit-error-on-syntax-error))
       end
       assert_include(stdout.string, "test/multiple_error.rbs:2:11...2:25: `void` type is only allowed in return type or generics parameter (RBS::WillSyntaxError)")
@@ -780,12 +824,16 @@ class Foo
         Dir.mktmpdir do |dir|
           (Pathname(dir) + 'a.rbs').write(rbs)
 
-          cli.run(["-I", dir, "validate"])
+          assert_cli_success do
+            cli.run(["-I", dir, "validate"])
+          end
 
           assert_match(/void|self|instance|class/, stdout.string)
 
-          cli.run(["-I", dir, "validate", "--no-exit-error-on-syntax-error"])
-          assert_raises SystemExit do
+          assert_cli_success do
+            cli.run(["-I", dir, "validate", "--no-exit-error-on-syntax-error"])
+          end
+          refute_cli_success do
             cli.run(["-I", dir, "validate", "--exit-error-on-syntax-error"])
           end
         end
@@ -802,7 +850,7 @@ def voice: [X] { () -> X } -> String
         end
         RBS
 
-        cli.run(["-I", dir, "validate"])
+        assert_cli_success cli.run(["-I", dir, "validate"])
       end
     end
   end
@@ -816,7 +864,7 @@ def void: () -> _Void
         end
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
         assert_match %r{a.rbs:2:18...2:23: Could not find _Void \(.*RBS::NoTypeFoundError.*\)}, stdout.string
@@ -833,7 +881,7 @@ def void: () -> voida
         end
         RBS
 
-        assert_raises SystemExit do
+        refute_cli_success do
           cli.run(["-I", dir, "validate"])
         end
         assert_match %r{a.rbs:2:18...2:23: Could not find voida \(.*RBS::NoTypeFoundError.*\)}, stdout.string
@@ -843,20 +891,20 @@ def void: () -> voida
 
   def test_constant
     with_cli do |cli|
-      cli.run(%w(constant Pathname))
-      cli.run(%w(constant --context File IO))
+      assert_cli_success cli.run(%w(constant Pathname))
+      assert_cli_success cli.run(%w(constant --context File IO))
     end
   end
 
   def test_version
     with_cli do |cli|
-      cli.run(%w(version))
+      assert_cli_success cli.run(%w(version))
     end
   end
 
   def test_paths
     with_cli do |cli|
-      cli.run(%w(-r pathname -I no-such-dir paths))
+      assert_cli_success cli.run(%w(-r pathname -I no-such-dir paths))
       assert_match %r{/core \(dir, core\)$}, stdout.string
       assert_match %r{/stdlib/pathname/0 \(dir, library, name=pathname\)$}, stdout.string
       assert_match %r{^no-such-dir \(absent\)$}, stdout.string
@@ -867,7 +915,7 @@ def test_paths_with_gem
     omit unless has_gem?("rbs-amber")
 
     with_cli do |cli|
-      cli.run(%w(-r rbs-amber paths))
+      assert_cli_success cli.run(%w(-r rbs-amber paths))
       assert_match %r{/core \(dir, core\)$}, stdout.string
       assert_match %r{/sig \(dir, library, name=rbs-amber\)$}, stdout.string
     end
@@ -877,7 +925,7 @@ def test_vendor
     Dir.mktmpdir do |d|
       Dir.chdir(d) do
         with_cli do |cli|
-          cli.run(%w(vendor --vendor-dir=dir1))
+          assert_cli_success cli.run(%w(vendor --vendor-dir=dir1))
 
           assert_predicate Pathname(d) + "dir1/core", :directory?
         end
@@ -891,7 +939,7 @@ def test_vendor_gem
     Dir.mktmpdir do |d|
       Dir.chdir(d) do
         with_cli do |cli|
-          cli.run(%w(-r rbs-amber vendor --vendor-dir=dir1))
+          assert_cli_success cli.run(%w(-r rbs-amber vendor --vendor-dir=dir1))
 
           assert_predicate Pathname(d) + "dir1/rbs-amber-1.0.0", :directory?
         end
@@ -919,7 +967,7 @@ def foo: () -> void
       RBS
 
       with_cli do |cli|
-        assert_raises(SystemExit) { cli.run(%W(parse #{dir})) }
+        refute_cli_success { cli.run(%W(parse #{dir})) }
 
         assert_equal [
           "#{dir}/semantics_error.rbs:2:10...2:11: Syntax error: expected a token `pCOLON`, token=`.` (pDOT) (RBS::ParsingError)",
@@ -937,10 +985,10 @@ def foo: () -> void
 
   def test_parse_e
     with_cli do |cli|
-      cli.run(['parse', '-e', 'class C end'])
+      assert_cli_success cli.run(['parse', '-e', 'class C end'])
       assert_empty stdout.string
 
-      assert_raises(SystemExit) { cli.run(['parse', '-e', 'class C en']) }
+      refute_cli_success { cli.run(['parse', '-e', 'class C en']) }
       assert_equal [
         "-e:1:8...1:10: Syntax error: unexpected token for class/module declaration member, token=`en` (tLIDENT) (RBS::ParsingError)",
         "",
@@ -952,10 +1000,10 @@ def test_parse_e
 
   def test_parse_type
     with_cli do |cli|
-      cli.run(['parse', '--type', '-e', 'bool'])
+      assert_cli_success cli.run(['parse', '--type', '-e', 'bool'])
       assert_empty stdout.string
 
-      assert_raises(SystemExit) { cli.run(['parse', '--type', '-e', '?']) }
+      refute_cli_success { cli.run(['parse', '--type', '-e', '?']) }
       assert_equal [
         "-e:1:0...1:1: Syntax error: unexpected token for simple type, token=`?` (pQUESTION) (RBS::ParsingError)",
         "",
@@ -967,10 +1015,10 @@ def test_parse_type
 
   def test_parse_method_type
     with_cli do |cli|
-      cli.run(['parse', '--method-type', '-e', '() -> void'])
+      assert_cli_success cli.run(['parse', '--method-type', '-e', '() -> void'])
       assert_empty stdout.string
 
-      assert_raises(SystemExit) { cli.run(['parse', '--method-type', '-e', '()']) }
+      refute_cli_success cli.run(['parse', '--method-type', '-e', '()'])
       assert_equal [
         "-e:1:2...1:2: Syntax error: expected a token `pARROW`, token=`` (pEOF) (RBS::ParsingError)",
         "",
@@ -987,13 +1035,8 @@ def cli.has_parser?
           false
         end
 
-        assert_raises SystemExit do
-          cli.run(%w(prototype rb))
-        end
-
-        assert_raises SystemExit do
-          cli.run(%w(prototype rbi))
-        end
+        refute_cli_success cli.run(%w(prototype rb))
+        refute_cli_success cli.run(%w(prototype rbi))
 
         assert_equal "Not supported on this interpreter (ruby).\n", stdout.string.lines[0]
         assert_equal "Not supported on this interpreter (ruby).\n", stdout.string.lines[1]
@@ -1035,7 +1078,7 @@ module C
 
       Dir.chdir(dir) do
         with_cli do |cli|
-          cli.run(%w(prototype rb --out_dir=sig lib Gemfile))
+          assert_cli_success cli.run(%w(prototype rb --out_dir=sig lib Gemfile))
 
           assert_equal <<-EOM, cli.stdout.string
 Processing `lib`...
@@ -1074,7 +1117,7 @@ module A
 
       Dir.chdir(dir) do
         with_cli do |cli|
-          cli.run(%w(prototype rb --out_dir=sig --base_dir=lib test/a_test.rb))
+          assert_cli_success cli.run(%w(prototype rb --out_dir=sig --base_dir=lib test/a_test.rb))
 
           assert_equal <<-EOM, cli.stdout.string
 Processing `test/a_test.rb`...
@@ -1094,13 +1137,13 @@ def test_prototype_batch_syntax_error
 
       (dir + "lib").mkdir
       (dir + "lib/a.rb").write(<<-RUBY)
-class A < <%= @superclass %>
+class A < {{SUPER_CLASS}}
 end
       RUBY
 
       Dir.chdir(dir) do
         with_cli do |cli|
-          cli.run(%w(prototype rb --out_dir=sig lib))
+          assert_cli_success cli.run(%w(prototype rb --out_dir=sig lib))
 
           assert_equal <<-EOM, cli.stdout.string
 Processing `lib`...
@@ -1121,7 +1164,7 @@ def test_prototype__runtime__todo
           begin
             old = $stderr
             $stderr = cli.stderr
-            cli.run(%w(prototype runtime --todo ::Object))
+            assert_cli_success cli.run(%w(prototype runtime --todo ::Object))
           ensure
             $stderr = old
           end
@@ -1155,9 +1198,9 @@ def foo: () -> void
         # `exit` is a common shell built-in command.
         assert_rbs_test_no_errors(cli, dir, %w(--target ::Foo exit))
 
-        assert_raises(SystemExit) { cli.run(%w(test)) }
-        assert_raises(SystemExit) { cli.run(%W(-I #{dir} test)) }
-        assert_raises(SystemExit) { cli.run(%W(-I #{dir} test --target ::Foo)) }
+        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))
       end
     end
   end
@@ -1568,7 +1611,7 @@ def x: () -> untyped
       RBS
 
       with_cli do |cli|
-        cli.run(['subtract', minuend.to_s, subtrahend.to_s])
+        assert_cli_success cli.run(['subtract', minuend.to_s, subtrahend.to_s])
         assert_empty stderr.string
         assert_equal <<~RBS, stdout.string
           use A::B
@@ -1608,7 +1651,9 @@ def y: () -> untyped
       RBS
 
       with_cli do |cli|
-        cli.run(['subtract', minuend.to_s, '--subtrahend', subtrahend_1.to_s, '--subtrahend', subtrahend_2.to_s])
+        assert_cli_success {
+          cli.run(['subtract', minuend.to_s, '--subtrahend', subtrahend_1.to_s, '--subtrahend', subtrahend_2.to_s])
+        }
         assert_empty stderr.string
         assert_equal <<~RBS, stdout.string
           use A::B
@@ -1641,7 +1686,7 @@ def x: () -> untyped
       RBS
 
       with_cli do |cli|
-        cli.run(['subtract', '--write', minuend.to_s, subtrahend.to_s])
+        assert_cli_success cli.run(['subtract', '--write', minuend.to_s, subtrahend.to_s])
         assert_empty stderr.string
         assert_empty stdout.string
         assert_equal minuend.read, <<~RBS
@@ -1674,7 +1719,7 @@ def x: () -> untyped
       RBS
 
       with_cli do |cli|
-        cli.run(['subtract', '--write', minuend.to_s, subtrahend.to_s])
+        assert_cli_success cli.run(['subtract', '--write', minuend.to_s, subtrahend.to_s])
         assert_empty stderr.string
         assert_empty stdout.string
         refute_predicate minuend, :exist?
@@ -1684,7 +1729,9 @@ def x: () -> untyped
 
   def assert_rbs_test_no_errors cli, dir, arg_array
     args = ['-I', dir.to_s, 'test', *arg_array]
-    assert_instance_of Process::Status, cli.run(args)
+    exit_status = cli.run(args)
+    assert_instance_of Integer, exit_status
+    assert_predicate exit_status, :zero?
   end
 
   def mktmp_diff_case
@@ -1730,7 +1777,9 @@ class Foo
   def test_diff_markdown
     mktmp_diff_case do |dir1, dir2|
       with_cli do |cli|
-        cli.run(['diff', '--format', 'markdown', '--type-name', 'Foo', '--before', dir1.to_s, '--after', dir2.to_s])
+        assert_cli_success {
+          cli.run(['diff', '--format', 'markdown', '--type-name', 'Foo', '--before', dir1.to_s, '--after', dir2.to_s])
+        }
 
         assert_equal <<~MARKDOWN, stdout.string
           | before | after |
@@ -1747,7 +1796,9 @@ def test_diff_markdown
   def test_diff_diff
     mktmp_diff_case do |dir1, dir2|
       with_cli do |cli|
-        cli.run(['diff', '--format', 'diff', '--type-name', 'Foo', '--before', dir1.to_s, '--after', dir2.to_s])
+        assert_cli_success do
+          cli.run(['diff', '--format', 'diff', '--type-name', 'Foo', '--before', dir1.to_s, '--after', dir2.to_s])
+        end
 
         assert_equal <<~DIFF, stdout.string
           - def qux: (untyped) -> untyped