Add more next/previous tests

Author: jacwah

src/renderer/html_handlebars/helpers/navigation.rs

@@ -140,12 +140,11 @@ pub fn next(_h: &Helper, r: &Handlebars, rc: &mut RenderContext) -> Result<(), R
 mod tests {
    use super::*;
 
+   static TEMPLATE: &'static str =
+      "{{#previous}}{{title}}: {{link}}{{/previous}}|{{#next}}{{title}}: {{link}}{{/next}}";
+
    #[test]
    fn test_next_previous() {
-      let template = "
-         {{#previous}}{{title}}: {{link}}{{/previous}}
-         {{#next}}{{title}}: {{link}}{{/next}}";
-
       let data = json!({
          "name": "two",
          "path": "two.path",
@@ -169,8 +168,67 @@ mod tests {
       h.register_helper("previous", Box::new(previous));
       h.register_helper("next", Box::new(next));
 
-      assert_eq!(h.template_render(template, &data).unwrap(), "
-         one: one.html
-         three: three.html");
+      assert_eq!(
+         h.template_render(TEMPLATE, &data).unwrap(),
+         "one: one.html|three: three.html");
+   }
+
+   #[test]
+   fn test_first() {
+      let data = json!({
+         "name": "one",
+         "path": "one.path",
+         "chapters": [
+            {
+               "name": "one",
+               "path": "one.path"
+            },
+            {
+               "name": "two",
+               "path": "two.path",
+            },
+            {
+               "name": "three",
+               "path": "three.path"
+            }
+         ]
+      });
+
+      let mut h = Handlebars::new();
+      h.register_helper("previous", Box::new(previous));
+      h.register_helper("next", Box::new(next));
+
+      assert_eq!(
+         h.template_render(TEMPLATE, &data).unwrap(),
+         "|two: two.html");
+   }
+   #[test]
+   fn test_last() {
+      let data = json!({
+         "name": "three",
+         "path": "three.path",
+         "chapters": [
+            {
+               "name": "one",
+               "path": "one.path"
+            },
+            {
+               "name": "two",
+               "path": "two.path",
+            },
+            {
+               "name": "three",
+               "path": "three.path"
+            }
+         ]
+      });
+
+      let mut h = Handlebars::new();
+      h.register_helper("previous", Box::new(previous));
+      h.register_helper("next", Box::new(next));
+
+      assert_eq!(
+         h.template_render(TEMPLATE, &data).unwrap(),
+         "two: two.html|");
    }
 }