add post test

spec/http_spec.cr

@@ -1,6 +1,9 @@
 require "./spec_helper"
 WebMock.stub(:get, "example.com")
 WebMock.stub(:get, "http://example.com/?foo=bar&foo1=bar2")
+WebMock.stub(:post, "http://example.com/post").
+         with(body: "email=foobar", headers: {"Content-Type" => "application/x-www-form-urlencoded"}).
+         to_return(body: "success")
 
 describe "Mechanize HTTP test" do
   it "simple GET" do
@@ -37,4 +40,12 @@ describe "Mechanize HTTP test" do
     agent.request_headers.empty?.should eq false
     agent.request_headers["Foo"].should eq "Bar"
   end
+
+  it "simple POST" do
+    agent = Mechanize.new
+    query = { "email" => "foobar" }
+    page = agent.post("http://example.com/post", query: query)
+    page.body.should eq "success"
+    page.code.should eq 200
+  end
 end

src/mechanize/form/field.cr

@@ -5,10 +5,10 @@ class MechanizeCr::FormContent::Field
   getter type      : String
   getter raw_value : String
 
-  def initialize(node : Node | Myhtml::Node)
+  def initialize(node : Node | Myhtml::Node, value = "")
     @node = node
     @name = node.fetch("name", "")
-    @value = node.fetch("value", "")
+    @value = value || node.fetch("value", "")
     @type = node.fetch("type", "")
     @raw_value = value
   end