Use rspec-parameterized for table-based tests

Gemfile

@@ -324,6 +324,7 @@ group :development, :test do
   gem 'spinach-rerun-reporter', '~> 0.0.2'
   gem 'rspec_profiling', '~> 0.0.5'
   gem 'rspec-set', '~> 0.1.3'
+  gem 'rspec-parameterized'
 
   # Prevent occasions where minitest is not bundled in packaged versions of ruby (see #3826)
   gem 'minitest', '~> 5.7.0'

Gemfile.lock

@@ -2,6 +2,7 @@ GEM
   remote: https://rubygems.org/
   specs:
     RedCloth (4.3.2)
+    abstract_type (0.0.7)
     ace-rails-ap (4.1.2)
     actionmailer (4.2.8)
       actionpack (= 4.2.8)
@@ -41,6 +42,9 @@ GEM
       tzinfo (~> 1.1)
     acts-as-taggable-on (4.0.0)
       activerecord (>= 4.0)
+    adamantium (0.2.0)
+      ice_nine (~> 0.11.0)
+      memoizable (~> 0.4.0)
     addressable (2.3.8)
     after_commit_queue (1.3.0)
       activerecord (>= 3.0)
@@ -124,6 +128,9 @@ GEM
     coercible (1.0.0)
       descendants_tracker (~> 0.0.1)
     colorize (0.7.7)
+    concord (0.1.5)
+      adamantium (~> 0.2.0)
+      equalizer (~> 0.0.9)
     concurrent-ruby (1.0.5)
     concurrent-ruby-ext (1.0.5)
       concurrent-ruby (= 1.0.5)
@@ -461,6 +468,8 @@ GEM
       mime-types (>= 1.16, < 4)
     mail_room (0.9.1)
     memoist (0.15.0)
+    memoizable (0.4.2)
+      thread_safe (~> 0.3, >= 0.3.1)
     method_source (0.8.2)
     mime-types (2.99.3)
     mimemagic (0.3.0)
@@ -601,6 +610,11 @@ GEM
     premailer-rails (1.9.7)
       actionmailer (>= 3, < 6)
       premailer (~> 1.7, >= 1.7.9)
+    proc_to_ast (0.1.0)
+      coderay
+      parser
+      unparser
+    procto (0.0.3)
     prometheus-client-mmap (0.7.0.beta11)
       mmap2 (~> 2.2, >= 2.2.7)
     pry (0.10.4)
@@ -709,6 +723,10 @@ GEM
       chunky_png
     rqrcode-rails3 (0.1.7)
       rqrcode (>= 0.4.2)
+    rspec (3.6.0)
+      rspec-core (~> 3.6.0)
+      rspec-expectations (~> 3.6.0)
+      rspec-mocks (~> 3.6.0)
     rspec-core (3.6.0)
       rspec-support (~> 3.6.0)
     rspec-expectations (3.6.0)
@@ -717,6 +735,12 @@ GEM
     rspec-mocks (3.6.0)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.6.0)
+    rspec-parameterized (0.4.0)
+      binding_of_caller
+      parser
+      proc_to_ast
+      rspec (>= 2.13, < 4)
+      unparser
     rspec-rails (3.6.0)
       actionpack (>= 3.0)
       activesupport (>= 3.0)
@@ -883,6 +907,14 @@ GEM
       get_process_mem (~> 0)
       unicorn (>= 4, < 6)
     uniform_notifier (1.10.0)
+    unparser (0.2.6)
+      abstract_type (~> 0.0.7)
+      adamantium (~> 0.2.0)
+      concord (~> 0.1.5)
+      diff-lcs (~> 1.3)
+      equalizer (~> 0.0.9)
+      parser (>= 2.3.1.2, < 2.5)
+      procto (~> 0.0.2)
     url_safe_base64 (0.2.2)
     validates_hostname (1.0.6)
       activerecord (>= 3.0)
@@ -1085,6 +1117,7 @@ DEPENDENCIES
   responders (~> 2.0)
   rouge (~> 2.0)
   rqrcode-rails3 (~> 0.1.7)
+  rspec-parameterized
   rspec-rails (~> 3.6.0)
   rspec-retry (~> 0.4.5)
   rspec-set (~> 0.1.3)

doc/development/testing.md

@@ -268,6 +268,43 @@ end
 - Avoid scenario titles that add no information, such as "successfully".
 - Avoid scenario titles that repeat the feature title.
 
+### Table-based / Parameterized tests
+
+This style of testing is used to exercise one piece of code with a comprehensive
+range of inputs. By specifying the test case once, alongside a table of inputs
+and the expected output for each, your tests can be made easier to read and more
+compact.
+
+We use the [rspec-parameterized](https://github.com/tomykaira/rspec-parameterized)
+gem. A short example, using the table syntax and checking Ruby equality for a
+range of inputs, might look like this:
+
+```ruby
+describe "#==" do
+  using Rspec::Parameterized::TableSyntax
+
+  let(:project1) { create(:project) }
+  let(:project2) { create(:project) }
+  where(:a, :b, :result) do
+    1         | 1        | true
+    1         | 2        | false
+    true      | true     | true
+    true      | false    | false
+    project1  | project1 | true
+    project2  | project2 | true
+    project 1 | project2 | false
+  end
+
+  with_them do
+    it { expect(a == b).to eq(result) }
+
+    it 'is isomorphic' do
+      expect(b == a).to eq(result)
+    end
+  end
+end
+```
+
 ### Matchers
 
 Custom matchers should be created to clarify the intent and/or hide the

spec/spec_helper.rb

@@ -8,6 +8,7 @@ require File.expand_path("../../config/environment", __FILE__)
 require 'rspec/rails'
 require 'shoulda/matchers'
 require 'rspec/retry'
+require 'rspec-parameterized'
 
 rspec_profiling_is_configured =
   ENV['RSPEC_PROFILING_POSTGRES_URL'].present? ||