github · cheshire137 · Oct 11, 2017 · Sep 28, 2017 · Sep 28, 2017 · Sep 28, 2017
diff --git a/Gemfile b/Gemfile
@@ -1,6 +1,7 @@
 source "https://rubygems.org"
 
 group :test do
+  gem "fastimage", "~> 2.1.0"
   gem "minitest", "~> 5.10.3"
   gem "rake"
   gem "rubocop", "~> 0.50.0"

diff --git a/Gemfile.lock b/Gemfile.lock
@@ -2,6 +2,7 @@ GEM
   remote: https://rubygems.org/
   specs:
     ast (2.3.0)
+    fastimage (2.1.0)
     minitest (5.10.3)
     parallel (1.12.0)
     parser (2.4.0.0)
@@ -25,10 +26,11 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  fastimage (~> 2.1.0)
   minitest (~> 5.10.3)
   rake
   rubocop (~> 0.50.0)
   safe_yaml (~> 1.0.4)
 
 BUNDLED WITH
-   1.15.3
+   1.15.4
diff --git a/README.md b/README.md
@@ -4,6 +4,16 @@
 
 <img src="https://user-images.githubusercontent.com/1840802/31236555-436777c4-a9a9-11e7-8377-c5c4c4c7722e.png" width="650" />
 
+There are some lint tests in place to ensure each topic is formatted in the way we expect. Travis
+CI will run the tests automatically. If you want to run the tests yourself locally, you will need
+Ruby and Bundler installed.
+
+You can run the tests using:
+
+```bash
+script/cibuild
+```
+
 Topic pages, curated by the community.
 
 [Topics](https://help.github.com/articles/about-topics/) help you explore repositories in a particular subject area, learn more about a subject area, and find projects to contribute to.

diff --git a/test/test_helper.rb b/test/test_helper.rb
@@ -1,11 +1,13 @@
 require "minitest/autorun"
+require "fastimage"
 require "yaml"
 
 IMAGE_EXTENSIONS = %w[.jpg .jpeg .png].freeze
-
+IMAGE_WIDTH = 288
+IMAGE_HEIGHT = 288
+MAX_IMAGE_FILESIZE_IN_BYTES = 65_000
 VALID_METADATA_KEYS = %w[aliases created_by display_name github_url logo related
                          released short_description topic url wikipedia_url].freeze
-
 REQUIRED_METADATA_KEYS = %w[topic short_description].freeze
 
 MAX_TOPIC_LENGTH = 35

diff --git a/test/topics_test.rb b/test/topics_test.rb
@@ -59,14 +59,26 @@
         assert File.file?(path), "expected #{path} to be a file"
       end
 
-      it "has only one image with the right name" do
+      it "has at most one image with the right name, type, and dimensions" do
         paths = image_paths_for(topic)
 
         assert paths.size <= 1, "expected at most one image, found #{paths.size}"
 
         if path = paths.first
           assert_equal topic, File.basename(path, File.extname(path)),
                        "expected image to be named [topic].[extension]"
+
+          width, height = FastImage.size(path)
+          assert_equal IMAGE_WIDTH, width, "topic images should be #{IMAGE_WIDTH}px wide"
+          assert_equal IMAGE_HEIGHT, height, "topic images should be #{IMAGE_HEIGHT}px tall"
+
+          assert_includes IMAGE_EXTENSIONS, ".#{FastImage.type(path)}",
+                          "topic images should be one of #{IMAGE_EXTENSIONS.join(', ')}"
+
+          file_size = FastImage.new(path).content_length
+          assert file_size <= MAX_IMAGE_FILESIZE_IN_BYTES,
+                 "topic images should not exceed #{MAX_IMAGE_FILESIZE_IN_BYTES} bytes, got " \
+                 "#{file_size} bytes"
         end
       end
 

diff --git a/topics/bitcoin/bitcoin.png b/topics/bitcoin/bitcoin.png
diff --git a/topics/elixir/elixir.png b/topics/elixir/elixir.png
diff --git a/topics/sketch/sketch.png b/topics/sketch/sketch.png