issue#58 implement Node#selected

Author: Mifrill

lib/ferrum/node.rb

@@ -127,6 +127,18 @@ def attribute(name)
       evaluate("this.getAttribute('#{name}')")
     end
 
+    def selected
+      function = <<~JS
+        function(element) {
+          if (element.nodeName.toLowerCase() !== 'select') {
+            throw new Error('Element is not a <select> element.');
+          }
+          return Array.from(element).filter(option => option.selected).map((option) => option.text);
+        }
+      JS
+      page.evaluate_func(function, self)
+    end
+
     def evaluate(expression)
       page.evaluate_on(node: self, expression: expression)
     end

spec/node_spec.rb

@@ -83,13 +83,33 @@ module Ferrum
       expect(links.first.text).to eq("Open for match")
     end
 
-    it "picks option in select" do
-      browser.goto("/ferrum/form")
-      input = browser.at_xpath("//*[@id='form_title']")
-      expect(input.value).to eq "Mrs"
-      input.click
-      input.type("Miss", :Enter)
-      expect(input.value).to eq "Miss"
+    describe "#selected" do
+      before do
+        browser.goto("/ferrum/form")
+      end
+
+      it "returns texts of selected options" do
+        expect(browser.at_xpath("//*[@id='form_region']").selected).to eq(["Norway"])
+      end
+
+      context "when options exists but no selected option" do
+        it "returns first option text as default value" do
+          expect(browser.at_xpath("//*[@id='form_title']").selected).to eq(["Mrs"])
+        end
+      end
+
+      context "when no selected options" do
+        it "returns empty array" do
+          expect(browser.at_xpath("//*[@id='form_tendency']").selected).to eq([])
+        end
+      end
+
+      context "when selector is not <select>" do
+        it "raises JavaScriptError with proper message" do
+          expect { browser.at_xpath("//*[@id='customer_name']").selected }.
+            to raise_exception(Ferrum::JavaScriptError, /Element is not a <select> element/)
+        end
+      end
     end
 
     context "when the element is not in the viewport" do