diff --git a/test/run_all.rb b/test/run_all.rb
new file mode 100644
index 0000000..fa1309c
--- /dev/null
+++ b/test/run_all.rb
@@ -0,0 +1,6 @@
+$LOAD_PATH.unshift(File.expand_path('../lib', __dir__))
+$LOAD_PATH.unshift(__dir__)
+
+require 'minitest/autorun'
+
+Dir[File.join(__dir__, 'test_*.rb')].sort.each { |file| require file }
diff --git a/test/support.rb b/test/support.rb
new file mode 100644
index 0000000..8b513ee
--- /dev/null
+++ b/test/support.rb
@@ -0,0 +1,24 @@
+require 'prism'
+require 'stringio'
+
+module TestSupport
+  def env_for(method, path, headers: {}, body: nil, cookies: nil)
+    path_part, query = path.split('?', 2)
+    env = {
+      'REQUEST_METHOD' => method.to_s.upcase,
+      'PATH_INFO' => path_part,
+      'QUERY_STRING' => query.to_s,
+      'rack.input' => StringIO.new(body || ''),
+      'CONTENT_LENGTH' => (body ? body.bytesize.to_s : '0')
+    }
+    headers.each do |name, value|
+      if name.downcase == 'content-type'
+        env['CONTENT_TYPE'] = value
+      else
+        env["HTTP_#{name.upcase.tr('-', '_')}"] = value
+      end
+    end
+    env['HTTP_COOKIE'] = cookies if cookies
+    env
+  end
+end
diff --git a/test/test_inflector.rb b/test/test_inflector.rb
new file mode 100644
index 0000000..155e102
--- /dev/null
+++ b/test/test_inflector.rb
@@ -0,0 +1,37 @@
+require 'minitest/autorun'
+require 'prism'
+
+class InflectorTest < Minitest::Test
+  include Prism::Inflector
+
+  def test_underscore
+    assert_equal 'posts_controller', underscore('PostsController')
+    assert_equal 'html_parser', underscore('HTMLParser')
+  end
+
+  def test_camelize
+    assert_equal 'PostsController', camelize('posts_controller')
+  end
+
+  def test_pluralize
+    assert_equal 'posts', pluralize('post')
+    assert_equal 'categories', pluralize('category')
+    assert_equal 'boxes', pluralize('box')
+    assert_equal 'leaves', pluralize('leaf')
+  end
+
+  def test_singularize
+    assert_equal 'category', singularize('categories')
+    assert_equal 'post', singularize('posts')
+    assert_equal 'box', singularize('boxes')
+  end
+
+  def test_tableize
+    assert_equal 'categories', tableize('Category')
+    assert_equal 'posts', tableize('Post')
+  end
+
+  def test_classify
+    assert_equal 'Category', classify('categories')
+  end
+end
diff --git a/test/test_request.rb b/test/test_request.rb
new file mode 100644
index 0000000..7ef944d
--- /dev/null
+++ b/test/test_request.rb
@@ -0,0 +1,46 @@
+require 'minitest/autorun'
+require 'prism'
+require 'support'
+
+class RequestTest < Minitest::Test
+  include TestSupport
+
+  def test_query_params
+    request = Prism::Request.new(env_for('GET', '/s?q=ruby&page=3'))
+    assert_equal 'ruby', request.params['q']
+    assert_equal '3', request.params['page']
+  end
+
+  def test_json_body
+    payload = JSON.generate(name: 'foksiu', role: 'admin')
+    request = Prism::Request.new(env_for('POST', '/u', headers: { 'Content-Type' => 'application/json' }, body: payload))
+    assert_equal 'foksiu', request.params['name']
+    assert_equal 'admin', request.params[:role]
+  end
+
+  def test_form_body
+    request = Prism::Request.new(env_for('POST', '/u', headers: { 'Content-Type' => 'application/x-www-form-urlencoded' }, body: 'a=1&b=two'))
+    assert_equal '1', request.params['a']
+    assert_equal 'two', request.params['b']
+  end
+
+  def test_cookies
+    request = Prism::Request.new(env_for('GET', '/', cookies: 'foo=bar; baz=qux'))
+    assert_equal 'bar', request.cookies['foo']
+    assert_equal 'qux', request.cookies['baz']
+  end
+
+  def test_headers
+    request = Prism::Request.new(env_for('GET', '/', headers: { 'X-Custom' => 'yes' }))
+    assert_equal 'yes', request.headers['X-Custom']
+  end
+
+  def test_params_precedence
+    env = env_for('POST', '/x?id=query',
+                  headers: { 'Content-Type' => 'application/x-www-form-urlencoded' },
+                  body: 'id=body')
+    request = Prism::Request.new(env)
+    request.path_params = { 'id' => 'path' }
+    assert_equal 'path', request.params['id']
+  end
+end
diff --git a/test/test_response.rb b/test/test_response.rb
new file mode 100644
index 0000000..4175760
--- /dev/null
+++ b/test/test_response.rb
@@ -0,0 +1,32 @@
+require 'minitest/autorun'
+require 'prism'
+
+class ResponseTest < Minitest::Test
+  def test_defaults
+    status, headers, body = Prism::Response.new.finish
+    assert_equal 200, status
+    assert_equal 'text/html;charset=utf-8', headers['Content-Type']
+    assert_equal [], body
+  end
+
+  def test_write
+    response = Prism::Response.new
+    response << 'a'
+    response.write('b')
+    assert_equal %w[a b], response.finish[2]
+  end
+
+  def test_set_cookie
+    response = Prism::Response.new
+    response.set_cookie('token', 'abc def')
+    assert_includes response.headers['Set-Cookie'], 'token=abc+def'
+    assert_includes response.headers['Set-Cookie'], 'HttpOnly'
+  end
+
+  def test_multiple_cookies
+    response = Prism::Response.new
+    response.set_cookie('a', '1')
+    response.set_cookie('b', '2')
+    assert_equal 2, response.headers['Set-Cookie'].split("\n").size
+  end
+end
diff --git a/test/test_router.rb b/test/test_router.rb
new file mode 100644
index 0000000..53686cf
--- /dev/null
+++ b/test/test_router.rb
@@ -0,0 +1,94 @@
+require 'minitest/autorun'
+require 'prism'
+
+class RouterTest < Minitest::Test
+  def setup
+    @router = Prism::Router.new
+  end
+
+  def test_static_match
+    @router.add('GET', '/health') {}
+    matches = @router.matches('GET', '/health')
+    assert_equal 1, matches.size
+    assert_equal({}, matches.first[1])
+  end
+
+  def test_named_param
+    @router.add('GET', '/users/:id') {}
+    _, params = @router.matches('GET', '/users/42').first
+    assert_equal '42', params['id']
+  end
+
+  def test_multiple_params
+    @router.add('GET', '/users/:uid/posts/:pid') {}
+    _, params = @router.matches('GET', '/users/7/posts/99').first
+    assert_equal '7', params['uid']
+    assert_equal '99', params['pid']
+  end
+
+  def test_wildcard
+    @router.add('GET', '/files/*') {}
+    _, params = @router.matches('GET', '/files/a/b/c.txt').first
+    assert_equal ['a/b/c.txt'], params['splat']
+  end
+
+  def test_method_mismatch
+    @router.add('POST', '/submit') {}
+    assert_empty @router.matches('GET', '/submit')
+  end
+
+  def test_no_match
+    @router.add('GET', '/x') {}
+    assert_empty @router.matches('GET', '/y')
+  end
+
+  def test_param_unescape
+    @router.add('GET', '/say/:word') {}
+    _, params = @router.matches('GET', '/say/hello%20world').first
+    assert_equal 'hello world', params['word']
+  end
+
+  def test_dot_is_literal
+    @router.add('GET', '/a.b') {}
+    assert_empty @router.matches('GET', '/axb')
+    assert_equal 1, @router.matches('GET', '/a.b').size
+  end
+
+  def test_all_http_verbs_supported
+    %w[GET POST PUT PATCH DELETE OPTIONS HEAD].each do |verb|
+      @router.add(verb, '/verb-check') {}
+      assert_equal 1, @router.matches(verb, '/verb-check').size, "#{verb} should match"
+    end
+  end
+
+  def test_named_route_path
+    @router.add('GET', '/posts/:id', name: :post) {}
+    assert_equal '/posts/7', @router.path_to(:post, id: 7)
+  end
+
+  def test_named_route_path_escapes_values
+    @router.add('GET', '/search/:term', name: :search) {}
+    assert_equal '/search/hello%20world', @router.path_to(:search, term: 'hello world')
+  end
+
+  def test_named_route_missing_param_raises
+    @router.add('GET', '/posts/:id', name: :post) {}
+    assert_raises(ArgumentError) { @router.path_to(:post, {}) }
+  end
+
+  def test_unknown_named_route_raises
+    assert_raises(ArgumentError) { @router.path_to(:nope) }
+  end
+
+  def test_controller_route_flag
+    route = @router.add('GET', '/posts/:id', to: 'posts#show')
+    assert route.controller_route?
+    assert_equal 'posts', route.controller_name
+    assert_equal 'show', route.action_name
+  end
+
+  def test_block_route_is_not_a_controller_route
+    route = @router.add('GET', '/health') {}
+    refute route.controller_route?
+  end
+end