Implement a new matcher, only_load_at_most_models (#28)

* Add a .ruby-version file

* Start implementation of a only_load_at_most_models expectation

* Test and implement LTE behavior

* Add gitignore record for .byebug_history

* Add a test to catch the case where we do not load any users at all

* Improve our error message a little bit, write a failing test

* Update VERSION and CHANGELOG

Author: kellysutton

.gitignore

@@ -11,4 +11,5 @@
 # rspec failure tracking
 .rspec_status
 Gemfile.lock
-/gemfiles
+/gemfiles
+.byebug_history

.ruby-version

@@ -0,0 +1,2 @@
+2.7.5
+

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.7.0] - 2022-01-27
+### Added
+- A new matcher, `only_load_at_most_models`, will do a less-than-or-equal-to (<=) check on model counts. This is a method that makes tests less noisy as performance gets better.
+
 ## [0.6.0] - 2022-01-05
 ### Changed
 - Support Rails 7

VERSION

@@ -1 +1 @@
-0.6.0
+0.7.0

lib/ar_query_matchers.rb

@@ -97,6 +97,49 @@ def failure_text
         end
       end
 
+      # The following will fail because the call to `User` is not expected, even
+      # though the Payroll count is correct:
+      #
+      #    expect {
+      #       Payroll.count
+      #       Payroll.count
+      #       User.count
+      #    }.to only_load_at_most_models(
+      #       'Payroll' => 2,
+      #    )
+      #
+      # The following will succeed because the counts are exact:
+      #
+      #    expect {
+      #       Payroll.count
+      #       Payroll.count
+      #       User.count
+      #    }.to only_load_at_most_models(
+      #       'Payroll' => 2,
+      #       'User' => 1,
+      #    )
+      #
+      RSpec::Matchers.define(:only_load_at_most_models) do |expected = {}|
+        include MatcherConfiguration
+        include MatcherErrors
+
+        match do |block|
+          @query_stats = Queries::LoadCounter.instrument(&block)
+          expected_queries = Utility.remove_superfluous_expectations(expected)
+          actual_queries = @query_stats.query_counts
+
+          all_models = expected_queries.keys | actual_queries.keys
+
+          all_models.each do |model|
+            expect(actual_queries[model] || 0).to be <= expected_queries[model]
+          end
+        end
+
+        def failure_text
+          expectation_failed_message('load at most')
+        end
+      end
+
       RSpec::Matchers.define(:not_load_any_models) do
         include MatcherConfiguration
         include MatcherErrors

query-matchers.gemspec

@@ -32,6 +32,7 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency 'appraisal'
   spec.add_development_dependency 'bundler'
+  spec.add_development_dependency 'byebug'
   spec.add_development_dependency 'rake'
   spec.add_development_dependency 'rspec'
   spec.add_development_dependency 'rubocop'

spec/ar_query_matchers/query_matchers_spec.rb

@@ -167,4 +167,48 @@ def updates(amount)
       )
     end
   end
+
+  describe 'only_load_at_most_models' do
+    it 'succeeds' do
+      expect do
+        updates(1)
+        loads(5)
+        creates(1)
+      end.to only_load_at_most_models({ 'MockUser' => 5 })
+    end
+
+    context 'there are fewer requests for models' do
+      it 'succeeds' do
+        expect do
+          updates(1)
+          loads(4)
+          creates(1)
+        end.to only_load_at_most_models({ 'MockUser' => 5 })
+      end
+    end
+
+    context 'there is no request for something specified' do
+      it 'succeeds' do
+        expect do
+          updates(1)
+          creates(1)
+        end.to only_load_at_most_models({ 'MockUser' => 5 })
+      end
+    end
+
+    context 'there are more requests made' do
+      it 'fails' do
+        expect do
+          expect do
+            updates(1)
+            loads(6)
+            creates(1)
+          end.to only_load_at_most_models({ 'MockUser' => 5 })
+        end.to raise_error(
+          RSpec::Expectations::ExpectationNotMetError,
+          /Expected ActiveRecord to load at most {"MockUser"=>5}, got {"MockUser"=>6}.*Where unexpected queries came from:/m
+        )
+      end
+    end
+  end
 end