diff --git a/.gitignore b/.gitignore
index 7f25924..6e9aaca 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 /.crystal
 /.shards
+/shard.lock
 /lib
diff --git a/shard.lock b/shard.lock
index 4eab3f7..5f4ae93 100644
--- a/shard.lock
+++ b/shard.lock
@@ -2,5 +2,5 @@ version: 1.0
 shards:
   minitest:
     github: ysbaddaden/minitest.cr
-    version: 0.3.6
+    version: 0.4.0
 
diff --git a/src/webdriver.cr b/src/webdriver.cr
index 2436a4a..64e1ae4 100644
--- a/src/webdriver.cr
+++ b/src/webdriver.cr
@@ -16,7 +16,7 @@ module Selenium
     end
 
     def get(path)
-      headers = HTTP::Headers{ "Accept" => "application/json" }
+      headers = HTTP::Headers{"Accept" => "application/json"}
 
       {% if flag?(:DEBUG) %}
       puts "REQUEST: GET #{path}"
@@ -27,13 +27,13 @@ module Selenium
 
       {% if flag?(:DEBUG) %}
       puts "RESPONSE: #{response.status_code}"
-      p JSON.parse(response.body).raw
+      p JSON.parse(response.body)
       puts
       {% end %}
 
       case response.status_code
       when 200
-        JSON.parse(response.body).raw.as(Hash)
+        JSON.parse(response.body)
       else
         failure(response)
       end
@@ -46,7 +46,7 @@ module Selenium
       {% end %}
 
       if body
-        headers = HTTP::Headers{ "Content-Type" => "application/json; charset=UTF-8" }
+        headers = HTTP::Headers{"Content-Type" => "application/json; charset=UTF-8"}
         response = @client.post("#{@path}#{path}", headers, body.to_json)
       else
         response = @client.post("#{@path}#{path}")
@@ -54,13 +54,13 @@ module Selenium
 
       {% if flag?(:DEBUG) %}
       puts "RESPONSE: #{response.status_code}"
-      p JSON.parse(response.body).raw
+      p JSON.parse(response.body)
       puts
       {% end %}
 
       case response.status_code
       when 200
-        JSON.parse(response.body).raw.as(Hash)
+        JSON.parse(response.body)
       else
         failure(response)
       end
@@ -75,7 +75,7 @@ module Selenium
 
       {% if flag?(:DEBUG) %}
       puts "RESPONSE: #{response.status_code}"
-      p JSON.parse(response.body).raw
+      p JSON.parse(response.body)
       {% end %}
 
       raise Error.new(response.body) unless response.status_code == 200
@@ -84,10 +84,9 @@ module Selenium
 
     private def failure(response)
       if response.headers["Content-Type"].starts_with?("application/json")
-        body = JSON.parse(response.body).raw.as(Hash)
-        status = body["status"].as(Int)
-        value = body["value"].as(Hash)
-        raise Selenium.error_class(status).new(value["message"].as(String))
+        body = JSON.parse(response.body)
+        status = body["status"].as_i
+        raise Selenium.error_class(status).new(body["value"]["message"].as_s)
       end
       raise Error.new(response.body)
     end
diff --git a/src/webdriver/alert.cr b/src/webdriver/alert.cr
index b5bb73e..d0e53f7 100644
--- a/src/webdriver/alert.cr
+++ b/src/webdriver/alert.cr
@@ -10,7 +10,7 @@ module Selenium
     end
 
     def send_keys(sequence : String)
-      session.post("/alert_text", { value: sequence })
+      session.post("/alert_text", {value: sequence})
     end
 
     def accept
diff --git a/src/webdriver/errors.cr b/src/webdriver/errors.cr
index e975f46..4220f22 100644
--- a/src/webdriver/errors.cr
+++ b/src/webdriver/errors.cr
@@ -1,37 +1,61 @@
 module Selenium
   class Error < Exception; end
+
   class NoSuchDriver < Error; end
+
   class NoSuchElement < Error; end
+
   class NoSuchFrame < Error; end
+
   class UnknownCommand < Error; end
+
   class StaleElementReference < Error; end
+
   class ElementNotVisible < Error; end
+
   class InvalidElementState < Error; end
+
   class UnknownError < Error; end
+
   class ElementIsNotSelectable < Error; end
+
   class JavaScriptError < Error; end
+
   class XPathLookupError < Error; end
+
   class Timeout < Error; end
+
   class NoSuchWindow < Error; end
+
   class InvalidCookieDomain < Error; end
+
   class UnableToSetCookie < Error; end
+
   class UnexpectedAlertOpen < Error; end
+
   class NoAlertOpenError < Error; end
+
   class ScriptTimeout < Error; end
+
   class InvalidElementCoordinates < Error; end
+
   class IMENotAvailable < Error; end
+
   class IMEEngineActivationFailed < Error; end
+
   class InvalidSelector < Error; end
+
   class SessionNotCreatedException < Error; end
+
   class MoveTargetOutOfBounds < Error; end
 
   # :nodoc:
   protected def self.error_class(status)
     case status
-    when 6 then NoSuchDriver
-    when 7 then NoSuchElement
-    when 8 then NoSuchFrame
-    when 9 then UnknownCommand
+    when  6 then NoSuchDriver
+    when  7 then NoSuchElement
+    when  8 then NoSuchFrame
+    when  9 then UnknownCommand
     when 10 then StaleElementReference
     when 11 then ElementNotVisible
     when 12 then InvalidElementState
diff --git a/src/webdriver/session.cr b/src/webdriver/session.cr
index 6f7d344..e688acb 100644
--- a/src/webdriver/session.cr
+++ b/src/webdriver/session.cr
@@ -20,17 +20,17 @@ module Selenium
 
     getter driver : Webdriver
     getter! id : String
-    getter! capabilities : Hash(String, JSON::Type)
+    getter! capabilities : Hash(String, JSON::Any)
 
     def initialize(@driver, desired_capabilities = Webdriver::CAPABILITIES, required_capabilities = Webdriver::CAPABILITIES, url = "about:blank")
       body = {
-        "desiredCapabilities" => desired_capabilities,
+        "desiredCapabilities"  => desired_capabilities,
         "requiredCapabilities" => required_capabilities,
       }
       response = driver.post("/session", body)
 
-      @id = response["sessionId"].as(String)
-      @capabilities = response["value"].as(Hash)
+      @id = response["sessionId"].as_s
+      @capabilities = response["value"].as_h
 
       if url
         self.url = url
@@ -54,11 +54,11 @@ module Selenium
     end
 
     def url
-      get("/url").as(String)
+      get("/url").as_s
     end
 
     def url=(url)
-      post("/url", { url: url })
+      post("/url", {url: url})
     end
 
     def forward
@@ -82,15 +82,15 @@ module Selenium
     end
 
     def execute(script, *args)
-      post("/execute", { script: script, args: args })
+      post("/execute", {script: script, args: args})
     end
 
     def execute_async(script, *args)
-      post("/execute", { script: script, args: args })
+      post("/execute", {script: script, args: args})
     end
 
     def frame(identifier)
-      post("/frame", { id: identifier })
+      post("/frame", {id: identifier})
     end
 
     def parent_frame
@@ -103,31 +103,31 @@ module Selenium
     end
 
     def save_screenshot(path)
-      data = get("/screenshot").as(String)
+      data = get("/screenshot").as_s
       File.open(path, "w") { |file| Base64.decode(data, file) }
     end
 
     def find_element(by, selector, parent : WebElement? = nil)
-      url = parent ? "/element/#{ parent.id }/element" : "/element"
+      url = parent ? "/element/#{parent.id}/element" : "/element"
       value = post(url, {
         using: WebElement.locator_for(by),
-        value: selector
+        value: selector,
       })
-      WebElement.new(self, value.as(Hash))
+      WebElement.new(self, value.as_h)
     end
 
     def find_elements(by, selector, parent : WebElement? = nil)
-      url = parent ? "/element/#{ parent.id }/elements" : "/elements"
+      url = parent ? "/element/#{parent.id}/elements" : "/elements"
       value = post(url, {
         using: WebElement.locator_for(by),
-        value: selector
-      }).as(Array)
-      value.map { |item| WebElement.new(self, item.as(Hash)) }
+        value: selector,
+      }).as_a
+      value.map { |item| WebElement.new(self, item.as_h) }
     end
 
     def active_element
       value = post("/element/active")
-      WebElement.new(self, value.as(Hash))
+      WebElement.new(self, value.as_h)
     end
 
     def orientation
@@ -136,7 +136,7 @@ module Selenium
 
     def orientation=(value)
       raise ArgumentError.new unless %i(portrait landscape).includes?(value)
-      post("/orientation", { orientation: value.to_s.upcase })
+      post("/orientation", {orientation: value.to_s.upcase})
     end
 
     def alert
@@ -152,33 +152,33 @@ module Selenium
     end
 
     def click(button : MouseButton = MouseButton::LEFT)
-      post("/click", { button: button.value })
+      post("/click", {button: button.value})
     end
 
     def double_click(button : MouseButton = MouseButton::Left)
-      post("/doubleclick", { button: button.value })
+      post("/doubleclick", {button: button.value})
     end
 
     def button_down(button : MouseButton = MouseButton::Left)
-      post("/buttondown", { button: button.value })
+      post("/buttondown", {button: button.value})
     end
 
     def button_up(button : MouseButton = MouseButton::Left)
-      post("/buttonup", { button: button.value })
+      post("/buttonup", {button: button.value})
     end
 
     protected def get(path = "")
-      response = driver.get("/session/#{ id }#{ path }")
+      response = driver.get("/session/#{id}#{path}")
       response["value"]
     end
 
     protected def post(path, body = nil)
-      response = driver.post("/session/#{ id }#{ path }", body)
+      response = driver.post("/session/#{id}#{path}", body)
       response["value"]
     end
 
     protected def delete(path = "")
-      driver.delete("/session/#{ id }#{ path }")
+      driver.delete("/session/#{id}#{path}")
     end
   end
 end
diff --git a/src/webdriver/session/cookies.cr b/src/webdriver/session/cookies.cr
index c19d309..358a8d6 100644
--- a/src/webdriver/session/cookies.cr
+++ b/src/webdriver/session/cookies.cr
@@ -1,38 +1,40 @@
 module Selenium
   class Session
     struct Cookie
+      @json : JSON::Any
+
       def initialize(json)
-        @json = json.as(Hash(String, JSON::Type))
+        @json = json
       end
 
       def name
-        @json["name"].as(String)
+        @json["name"].as_s
       end
 
       def value
-        @json["value"].as(String)
+        @json["value"].as_s
       end
 
       def domain
-        @json["domain"].as(String)
+        @json["domain"].as_s
       end
 
       def path
-        @json["path"].as(String)
+        @json["path"].as_s
       end
 
       def expiry
         if timestamp = @json["expiry"]?
-          Time.epoch(timestamp.as(Int64))
+          Time.epoch(timestamp.as_i64)
         end
       end
 
       def http_only
-        @json["httpOnly"].as(Bool)
+        @json["httpOnly"].as_bool
       end
 
       def secure
-        @json["secure"].as(Bool)
+        @json["secure"].as_bool
       end
     end
 
@@ -50,7 +52,7 @@ module Selenium
 
       def each(&block)
         @session.get("/cookie")
-          .as(Array)
+          .as_a
           .each { |json| yield Cookie.new(json) }
       end
 
@@ -60,19 +62,19 @@ module Selenium
 
       def set(name, value, domain = nil, path = "/", http_only = false, secure = false)
         cookie = {
-          "name" => name,
-          "value" => value,
-          "path" => path,
+          "name"     => name,
+          "value"    => value,
+          "path"     => path,
           "httpOnly" => http_only,
-          "secure" => secure
+          "secure"   => secure,
         }
         cookie["domain"] = domain if domain
-        @session.post("/cookie", { cookie: cookie })
+        @session.post("/cookie", {cookie: cookie})
       end
 
       def to_a
         @session.get("/cookie")
-          .as(Array)
+          .as_a
           .map { |json| Cookie.new(json) }
       end
 
@@ -81,13 +83,13 @@ module Selenium
           expiry = Time.epoch(timestamp.as(Int64))
         end
         {
-          name: json["name"].as(String),
-          value: json["value"].as(String),
-          domain: json["domain"].as(String),
-          path: json["path"].as(String),
-          expiry: expiry,
+          name:      json["name"].as(String),
+          value:     json["value"].as(String),
+          domain:    json["domain"].as(String),
+          path:      json["path"].as(String),
+          expiry:    expiry,
           http_only: json["httpOnly"].as(Bool),
-          secure: json["secure"].as(Bool),
+          secure:    json["secure"].as(Bool),
         }
       end
     end
diff --git a/src/webdriver/web_element.cr b/src/webdriver/web_element.cr
index f26ba5e..9e2e9e7 100644
--- a/src/webdriver/web_element.cr
+++ b/src/webdriver/web_element.cr
@@ -1,24 +1,24 @@
 module Selenium
   class WebElement
     LOCATORS = {
-      id: "id",
-      name: "name",
-      tag_name: "tag name",
-      class_name: "class name",
-      css: "css selector",
-      link_text: "link text",
+      id:                "id",
+      name:              "name",
+      tag_name:          "tag name",
+      class_name:        "class name",
+      css:               "css selector",
+      link_text:         "link text",
       partial_link_test: "partial link text",
-      xpath: "xpath",
+      xpath:             "xpath",
     }
 
     def self.locator_for(by)
       locator = LOCATORS[by]
-      raise ArgumentError.new("Unsupported locator strategy: #{ by.inspect }") unless locator
+      raise ArgumentError.new("Unsupported locator strategy: #{by.inspect}") unless locator
       locator
     end
 
     # TODO: special keys
-    #KEYS = {
+    # KEYS = {
     #  NULL  U+E000
     #  Cancel  U+E001
     #  Help  U+E002
@@ -57,7 +57,7 @@ module Selenium
     #  Numpad 7  U+E021
     #  Numpad 8  U+E022
     #  Numpad 9  U+E023
-    #}
+    # }
 
     getter id : String
     private getter session : Session
@@ -65,11 +65,11 @@ module Selenium
     def initialize(@session, item)
       if id = item["ELEMENT"]?
         # JsonWireProtocol (obsolete)
-        @id = id.as(String)
+        @id = id.as_s
       else
         # W3C Webdriver
         identifier = item.keys.find(&.starts_with?("element-"))
-        @id = item[identifier].as(String)
+        @id = item[identifier].as_s
       end
     end
 
@@ -82,15 +82,15 @@ module Selenium
     end
 
     def text
-      get("/text").as(String)
+      get("/text").as_s
     end
 
     def name
-      get("/name").as(String)
+      get("/name").as_s
     end
 
     def attribute(name)
-      get("/attribute/#{ name }").as(String)
+      get("/attribute/#{name}").as_s
     end
 
     def click
@@ -106,7 +106,7 @@ module Selenium
     end
 
     def send_keys(sequence : Array)
-      post("/value", { value: sequence })
+      post("/value", {value: sequence})
     end
 
     def clear
@@ -114,39 +114,39 @@ module Selenium
     end
 
     def ==(other : WebElement)
-      get("/equals/#{ other.id }").as(Bool)
+      get("/equals/#{other.id}").as_bool
     end
 
     def displayed?
-      get("/displayed").as(Bool)
+      get("/displayed").as_bool
     end
 
     def location
-      get("/location").as(Hash)
+      get("/location")
     end
 
     def location_in_view
-      get("/location_in_view").as(Hash)
+      get("/location_in_view")
     end
 
     def size
-      get("/size").as(Hash)
+      get("/size")
     end
 
     def css(property)
-      get("/css/#{ property }").as(String)
+      get("/css/#{property}").as_s
     end
 
     def to_json(io)
-      { "ELEMENT" => id }.to_json(io)
+      {"ELEMENT" => id}.to_json(io)
     end
 
     protected def get(path)
-      session.get("/element/#{ id }#{ path }")
+      session.get("/element/#{id}#{path}")
     end
 
     protected def post(path, body = nil)
-      session.post("/element/#{ id }#{ path }", body)
+      session.post("/element/#{id}#{path}", body)
     end
   end
 end