diff --git a/.gitea/workflows/demo.yaml b/.gitea/workflows/demo.yaml
index 8ccf895..a19a073 100644
--- a/.gitea/workflows/demo.yaml
+++ b/.gitea/workflows/demo.yaml
@@ -38,7 +38,7 @@ jobs:
           ruby-version: '3.3'
           bundler-cache: true
 
-      - run: ruby app_test.rb
+      - run: bundle exec rspec
 
 
   release-image:
diff --git a/Gemfile b/Gemfile
index acfb954..0c1240d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -18,6 +18,6 @@ group :development do
   gem "rubocop"
   gem "rbs"
   gem "rack-test"
-  gem "test-unit"
+  gem "rspec"
   gem "standard"
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index 56dc5f1..0596fa7 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -4,6 +4,7 @@ GEM
     anyflake (0.0.1)
     ast (2.4.2)
     base64 (0.2.0)
+    diff-lcs (1.5.1)
     json (2.7.2)
     jwt (2.8.2)
       base64
@@ -20,7 +21,6 @@ GEM
     parser (3.3.3.0)
       ast (~> 2.4.1)
       racc
-    power_assert (2.0.3)
     prism (0.30.0)
     puma (6.4.2)
       nio4r (~> 2.0)
@@ -42,6 +42,19 @@ GEM
     regexp_parser (2.9.2)
     rexml (3.3.0)
       strscan
+    rspec (3.13.0)
+      rspec-core (~> 3.13.0)
+      rspec-expectations (~> 3.13.0)
+      rspec-mocks (~> 3.13.0)
+    rspec-core (3.13.0)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-support (3.13.1)
     rubocop (1.64.1)
       json (~> 2.3)
       language_server-protocol (>= 3.17.0)
@@ -91,8 +104,6 @@ GEM
       lint_roller (~> 1.1)
       rubocop-performance (~> 1.21.0)
     strscan (3.1.0)
-    test-unit (3.6.2)
-      power_assert
     tilt (2.3.0)
     ulid (1.4.0)
     unicode-display_width (2.5.0)
@@ -114,12 +125,12 @@ DEPENDENCIES
   rack-test
   rackup
   rbs
+  rspec
   rubocop
   ruby-lsp
   sinatra
   sinatra-contrib
   standard
-  test-unit
   ulid
   uuid7
 
diff --git a/app_test.rb b/app_test.rb
deleted file mode 100644
index 1d355db..0000000
--- a/app_test.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-ENV["APP_ENV"] = "test"
-
-require "./app"
-require "test/unit"
-require "rack/test"
-
-class ToyTest < Test::Unit::TestCase
-  include Rack::Test::Methods
-
-  def app
-    Sinatra::Application
-  end
-
-  def test_root
-    get "/"
-    assert last_response.ok?
-    assert_equal "hello there!\n", last_response.body
-  end
-end
diff --git a/spec/app_spec.rb b/spec/app_spec.rb
new file mode 100644
index 0000000..8c48c29
--- /dev/null
+++ b/spec/app_spec.rb
@@ -0,0 +1,21 @@
+ENV["APP_ENV"] = "test"
+
+require "./app"
+require "rspec"
+require "rack/test"
+
+describe "Toy App" do
+  include Rack::Test::Methods
+
+  def app
+    Sinatra::Application
+  end
+
+  context "test /" do
+    it "test root route" do
+      get "/"
+      expect(last_response).to be_ok
+      expect(last_response.body).to eq("hello there!\n")
+    end
+  end
+end