net/url: add testable examples for Values funcs

Change-Id: Id71f3d8d7c1ef7910d5d9497167dc677f2f0a2ef
Reviewed-on: https://go-review.googlesource.com/c/go/+/356535
Trust: Damien Neil <dneil@google.com>
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>

src/net/url/example_test.go

@@ -68,6 +68,84 @@ func ExampleValues() {
 	// [Jess Sarah Zoe]
 }
 
+func ExampleValues_Add() {
+	v := url.Values{}
+	v.Add("cat sounds", "meow")
+	v.Add("cat sounds", "mew")
+	v.Add("cat sounds", "mau")
+	fmt.Println(v["cat sounds"])
+
+	// Output:
+	// [meow mew mau]
+}
+
+func ExampleValues_Del() {
+	v := url.Values{}
+	v.Add("cat sounds", "meow")
+	v.Add("cat sounds", "mew")
+	v.Add("cat sounds", "mau")
+	fmt.Println(v["cat sounds"])
+
+	v.Del("cat sounds")
+	fmt.Println(v["cat sounds"])
+
+	// Output:
+	// [meow mew mau]
+	// []
+}
+
+func ExampleValues_Encode() {
+	v := url.Values{}
+	v.Add("cat sounds", "meow")
+	v.Add("cat sounds", "mew/")
+	v.Add("cat sounds", "mau$")
+	fmt.Println(v.Encode())
+
+	// Output:
+	// cat+sounds=meow&cat+sounds=mew%2F&cat+sounds=mau%24
+}
+
+func ExampleValues_Get() {
+	v := url.Values{}
+	v.Add("cat sounds", "meow")
+	v.Add("cat sounds", "mew")
+	v.Add("cat sounds", "mau")
+	fmt.Printf("%q\n", v.Get("cat sounds"))
+	fmt.Printf("%q\n", v.Get("dog sounds"))
+
+	// Output:
+	// "meow"
+	// ""
+}
+
+func ExampleValues_Has() {
+	v := url.Values{}
+	v.Add("cat sounds", "meow")
+	v.Add("cat sounds", "mew")
+	v.Add("cat sounds", "mau")
+	fmt.Println(v.Has("cat sounds"))
+	fmt.Println(v.Has("dog sounds"))
+
+	// Output:
+	// true
+	// false
+}
+
+func ExampleValues_Set() {
+	v := url.Values{}
+	v.Add("cat sounds", "meow")
+	v.Add("cat sounds", "mew")
+	v.Add("cat sounds", "mau")
+	fmt.Println(v["cat sounds"])
+
+	v.Set("cat sounds", "meow")
+	fmt.Println(v["cat sounds"])
+
+	// Output:
+	// [meow mew mau]
+	// [meow]
+}
+
 func ExampleURL() {
 	u, err := url.Parse("http://bing.com/search?q=dotnet")
 	if err != nil {