diff --git a/app/controllers/knowledge_explorer/knowledge_explorer_controller.rb b/app/controllers/knowledge_explorer/knowledge_explorer_controller.rb
index 0ac17c9..01632fb 100644
--- a/app/controllers/knowledge_explorer/knowledge_explorer_controller.rb
+++ b/app/controllers/knowledge_explorer/knowledge_explorer_controller.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module KnowledgeExplorer
   class KnowledgeExplorerController < ApplicationController
     requires_plugin 'knowledge-explorer'
diff --git a/assets/javascripts/discourse/components/knowledge-explorer-search.js.es6 b/assets/javascripts/discourse/components/knowledge-explorer-search.js.es6
index 55f442a..d4d9765 100644
--- a/assets/javascripts/discourse/components/knowledge-explorer-search.js.es6
+++ b/assets/javascripts/discourse/components/knowledge-explorer-search.js.es6
@@ -1,29 +1,10 @@
-import knowledgeExplorer from "discourse/plugins/discourse-knowledge-explorer/discourse/models/knowledge-explorer";
-
 export default Ember.Component.extend({
   classNames: "knowledge-explorer-search",
 
-  performSearch(term) {
-    if (term.length < this.siteSettings.min_search_term_length) {
-      this.set("searchResults", null);
-      return;
-    }
-
-    // query the search api
-    const tags = this.get("filterTags") || null;
-    if (tags && tags.includes(" ")) {
-      tags.join(" ");
-    }
-    knowledgeExplorer.search(tags, term).then(result => {
-      this.set("searchResults", result.topics || []);
-    });
-  },
-
   actions: {
-    onSearchTermChange(e) {
-      const term = e.target.value;
-      this.set("searchTerm", term);
-      Ember.run.debounce(this, this.performSearch, term, 250);
+    onSearchTermChange(event) {
+      const term = event.target.value;
+      Ember.run.debounce(this, this.onSearch, term, 250);
     }
   }
 });
diff --git a/assets/javascripts/discourse/components/knowledge-explorer-tag-list.js.es6 b/assets/javascripts/discourse/components/knowledge-explorer-tag-list.js.es6
deleted file mode 100644
index dd4e771..0000000
--- a/assets/javascripts/discourse/components/knowledge-explorer-tag-list.js.es6
+++ /dev/null
@@ -1,3 +0,0 @@
-export default Ember.Component.extend({
-  classNames: "knowledge-explorer-tags"
-});
diff --git a/assets/javascripts/discourse/components/knowledge-explorer-tag.js.es6 b/assets/javascripts/discourse/components/knowledge-explorer-tag.js.es6
index 4ca65d8..e741d64 100644
--- a/assets/javascripts/discourse/components/knowledge-explorer-tag.js.es6
+++ b/assets/javascripts/discourse/components/knowledge-explorer-tag.js.es6
@@ -1,17 +1,6 @@
 export default Ember.Component.extend({
   click() {
-    const tag = this.get("tag");
-    let filter = this.get("filterTags");
-    if (filter && filter.includes(tag.id)) {
-      filter = filter.replace(tag.id, "");
-      filter = filter.replace("  ", " ");
-      filter = filter.replace(/^\s+|\s+$/g, "");
-    } else if (filter) {
-      filter = `${filter} ${tag.id}`;
-    } else {
-      filter = tag.id;
-    }
-
-    this.set("filterTags", filter);
+    this.selectTag(this.tag);
+    return false;
   }
 });
diff --git a/assets/javascripts/discourse/components/knowledge-explorer-topic-link.js.es6 b/assets/javascripts/discourse/components/knowledge-explorer-topic-link.js.es6
index 13e489c..cc00a52 100644
--- a/assets/javascripts/discourse/components/knowledge-explorer-topic-link.js.es6
+++ b/assets/javascripts/discourse/components/knowledge-explorer-topic-link.js.es6
@@ -1,5 +1,6 @@
 export default Ember.Component.extend({
   click() {
-    this.set("selectedTopic", this.topic.id);
+    this.selectTopic(this.topic.id);
+    return false;
   }
 });
diff --git a/assets/javascripts/discourse/controllers/knowledge-explorer.js.es6 b/assets/javascripts/discourse/controllers/knowledge-explorer.js.es6
index 11eb492..dcfe8f9 100644
--- a/assets/javascripts/discourse/controllers/knowledge-explorer.js.es6
+++ b/assets/javascripts/discourse/controllers/knowledge-explorer.js.es6
@@ -2,6 +2,7 @@ import {
   default as computed,
   observes
 } from "ember-addons/ember-computed-decorators";
+import knowledgeExplorer from "discourse/plugins/discourse-knowledge-explorer/discourse/models/knowledge-explorer";
 
 export default Ember.Controller.extend({
   application: Ember.inject.controller(),
@@ -18,23 +19,48 @@ export default Ember.Controller.extend({
 
   selectedTopic: null,
 
+  searchCount: Ember.computed.readOnly("searchResults.length"),
+  emptySearchResults: Ember.computed.equal("searchCount", 0),
+
   @computed("searchResults")
   hasSearchResults(results) {
     return !!results;
   },
 
-  @computed("searchResults")
-  emptySearchResults(results) {
-    return results.length === 0;
-  },
-
-  @computed("searchResults")
-  searchCount(results) {
-    return results.length;
-  },
-
   @computed("filterTags")
   filtered(filterTags) {
     return !!filterTags;
+  },
+
+  actions: {
+    setSelectedTopic(topicID) {
+      this.set("selectedTopic", topicID);
+    },
+    updateSelectedTags(tag) {
+      let filter = this.filterTags;
+      if (filter && filter.includes(tag.id)) {
+        filter = filter.replace(tag.id, "");
+        filter = filter.replace("++", "+");
+        filter = filter.replace(/^\++|\++$/g, "");
+      } else if (filter) {
+        filter = `${filter}+${tag.id}`;
+      } else {
+        filter = tag.id;
+      }
+
+      this.set("filterTags", filter);
+    },
+    performSearch(term) {
+      if (term.length < this.siteSettings.min_search_term_length) {
+        this.set("searchResults", null);
+        return false;
+      }
+
+      const tags = this.get("filterTags") || null;
+
+      knowledgeExplorer.search(term, tags).then(result => {
+        this.set("searchResults", result.topics || []);
+      });
+    }
   }
 });
diff --git a/assets/javascripts/discourse/models/knowledge-explorer.js.es6 b/assets/javascripts/discourse/models/knowledge-explorer.js.es6
index 3f722b3..02178d7 100644
--- a/assets/javascripts/discourse/models/knowledge-explorer.js.es6
+++ b/assets/javascripts/discourse/models/knowledge-explorer.js.es6
@@ -1,13 +1,12 @@
 import { ajax } from "discourse/lib/ajax";
 
 export default {
-  search(tags, filter) {
-    if (tags) {
-      return ajax(
-        `/search.json?q=in:kb tags:${tags.replace(/ /g, "+")} ${filter}`
-      );
-    } else {
-      return ajax(`/search.json?q=in:kb ${filter}`);
-    }
+  //write as one liner
+  //use + instead of space for query param
+  search(filter, tags) {
+    let params = [filter];
+    if (tags) params.push(`tags:${tags}`);
+    const endpoint = `/search.json?q=in:kb ${params.join(" ")}`;
+    return ajax(endpoint);
   }
 };
diff --git a/assets/javascripts/discourse/templates/components/knowledge-explorer-tag-list.hbs b/assets/javascripts/discourse/templates/components/knowledge-explorer-tag-list.hbs
deleted file mode 100644
index bac6e6a..0000000
--- a/assets/javascripts/discourse/templates/components/knowledge-explorer-tag-list.hbs
+++ /dev/null
@@ -1,6 +0,0 @@
-{{#each tags as |tag|}}
-    {{knowledge-explorer-tag 
-      tag=tag
-      filterTags=filterTags
-    }}
-{{/each}}
diff --git a/assets/javascripts/discourse/templates/components/knowledge-explorer-topic-list.hbs b/assets/javascripts/discourse/templates/components/knowledge-explorer-topic-list.hbs
index 40cb789..f0b55fa 100644
--- a/assets/javascripts/discourse/templates/components/knowledge-explorer-topic-list.hbs
+++ b/assets/javascripts/discourse/templates/components/knowledge-explorer-topic-list.hbs
@@ -8,7 +8,7 @@
     <tr>
       <td class="main-link">
         <span class="link-top-line">
-          {{knowledge-explorer-topic-link topic=topic selectedTopic=selectedTopic}}
+          {{knowledge-explorer-topic-link topic=topic selectTopic=selectTopic}}
         </span>
         <span class="link-bottom-line">
           {{#each topic.tags as |tag|}}
diff --git a/assets/javascripts/discourse/templates/knowledge-explorer.hbs b/assets/javascripts/discourse/templates/knowledge-explorer.hbs
index 643ba74..c3ce7b2 100644
--- a/assets/javascripts/discourse/templates/knowledge-explorer.hbs
+++ b/assets/javascripts/discourse/templates/knowledge-explorer.hbs
@@ -4,16 +4,18 @@
   {{else}}
     <div class="knowledge-explorer-search">
       {{knowledge-explorer-search 
-        searchResults=searchResults 
-        searchTerm=searchTerm 
-        filterTags=filterTags
+        onSearch=(action "performSearch")
       }}
     </div>
     <div class="knowledge-explorer-browse">
-      {{knowledge-explorer-tag-list
-        tags=tags
-        filterTags=filterTags
-      }}
+      <div class="knowledge-explorer-tags">
+        {{#each tags as |tag|}}
+            {{knowledge-explorer-tag 
+              tag=tag
+              selectTag=(action "updateSelectedTags")
+            }}
+        {{/each}}
+      </div>
       <div class="knowledge-explorer-results">
       {{#if hasSearchResults}}
         {{#if emptySearchResults}}
@@ -22,13 +24,13 @@
           <div class="result-count">{{i18n 'knowledge_explorer.search.results' count=searchCount}}</div>
           {{knowledge-explorer-topic-list 
             topics=searchResults 
-            selectedTopic=selectedTopic
+            selectTopic=(action "setSelectedTopic")
           }}
         {{/if}}
       {{else}}
         {{knowledge-explorer-topic-list 
           topics=topics 
-          selectedTopic=selectedTopic
+          selectTopic=(action "setSelectedTopic")
         }}
       {{/if}}
       </div>
diff --git a/config/routes.rb b/config/routes.rb
index 9bd5161..60d6fdd 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_dependency "knowledge_explorer_constraint"
 
 KnowledgeExplorer::Engine.routes.draw do
diff --git a/lib/knowledge_explorer/engine.rb b/lib/knowledge_explorer/engine.rb
index f81ec2d..e31d9ce 100644
--- a/lib/knowledge_explorer/engine.rb
+++ b/lib/knowledge_explorer/engine.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ::KnowledgeExplorer
   class Engine < ::Rails::Engine
     isolate_namespace KnowledgeExplorer
diff --git a/lib/knowledge_explorer_constraint.rb b/lib/knowledge_explorer_constraint.rb
index 572d332..c954a35 100644
--- a/lib/knowledge_explorer_constraint.rb
+++ b/lib/knowledge_explorer_constraint.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class KnowledgeExplorerConstraint
   def matches?(request)
     SiteSetting.knowledge_explorer_enabled
diff --git a/plugin.rb b/plugin.rb
index 674f4e6..e66a959 100644
--- a/plugin.rb
+++ b/plugin.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # name: discourse-knowledge-explorer
 # about: A plugin to make it easy to explore and find knowledge base-type articles in Discourse
 # version: 0.1
diff --git a/spec/requests/knowledge_explorer_controller_spec.rb b/spec/requests/knowledge_explorer_controller_spec.rb
new file mode 100644
index 0000000..43cc39f
--- /dev/null
+++ b/spec/requests/knowledge_explorer_controller_spec.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe KnowledgeExplorer::KnowledgeExplorerController do
+  let!(:category) { Fabricate(:category) }
+  let!(:topic) { Fabricate(:topic, category: category) }
+  let!(:topic2) { Fabricate(:topic, category: category) }
+  let!(:tag) { Fabricate(:tag, topics: [topic], name: 'test') }
+
+  before do
+    SiteSetting.tagging_enabled = true
+    SiteSetting.knowledge_explorer_enabled = true
+    SiteSetting.knowledge_explorer_categories = category.id.to_s
+    SiteSetting.knowledge_explorer_tags = 'test'
+  end
+
+  describe 'knowledge explorer data' do
+    context 'when any user' do
+      it 'should return the right response' do
+        get '/knowledge-explorer.json'
+
+        expect(response.status).to eq(200)
+
+        json = JSON.parse(response.body)
+
+        expect(json['tags'].size).to eq(1)
+        expect(json['topics'].size).to eq(2)
+      end
+    end
+
+    context "when some knowledge explorer topics are private" do
+      let!(:group) { Fabricate(:group) }
+      let!(:private_category) { Fabricate(:private_category, group: group) }
+      let!(:private_topic) { Fabricate(:topic, category: private_category) }
+
+      before do
+        SiteSetting.knowledge_explorer_categories = "#{category.id}|#{private_category.id}"
+      end
+
+      it 'should not show topics in private categories without permissions' do
+        get '/knowledge-explorer.json'
+
+        json = JSON.parse(response.body)
+
+        expect(json['topics'].size).to eq(2)
+      end
+
+      it 'should show topics when users have permissions' do
+        admin = Fabricate(:admin)
+        sign_in(admin)
+
+        get '/knowledge-explorer.json'
+
+        json = JSON.parse(response.body)
+
+        expect(json['topics'].size).to eq(3)
+      end
+    end
+
+    context 'when filtering by tag' do
+      it 'should return a filtered list' do
+        get '/knowledge-explorer.json?tags=test'
+
+        expect(response.status).to eq(200)
+
+        json = JSON.parse(response.body)
+
+        expect(json['tags'].size).to eq(1)
+        expect(json['topics'].size).to eq(1)
+      end
+    end
+  end
+end