1 files changed, 64 insertions, 0 deletions
diff --git a/spec/support/matchers/exceed_query_limit.rb b/spec/support/matchers/exceed_query_limit.rb
new file mode 100644
index 00000000000..88d22a3ddd9
--- /dev/null
+++ b/spec/support/matchers/exceed_query_limit.rb
@@ -0,0 +1,64 @@
+RSpec::Matchers.define :exceed_query_limit do |expected|
+  supports_block_expectations
+
+  match do |block|
+    @subject_block = block
+    actual_count > expected_count + threshold
+  end
+
+  failure_message_when_negated do |actual|
+    threshold_message = threshold > 0 ? " (+#{@threshold})" : ''
+    counts = "#{expected_count}#{threshold_message}"
+    "Expected a maximum of #{counts} queries, got #{actual_count}:\n\n#{log_message}"
+  end
+
+  def with_threshold(threshold)
+    @threshold = threshold
+    self
+  end
+
+  def for_query(query)
+    @query = query
+    self
+  end
+
+  def threshold
+    @threshold.to_i
+  end
+
+  def expected_count
+    if expected.is_a?(ActiveRecord::QueryRecorder)
+      expected.count
+    else
+      expected
+    end
+  end
+
+  def actual_count
+    @actual_count ||= if @query
+                        recorder.log.select { |recorded| recorded =~ @query }.size
+                      else
+                        recorder.count
+                      end
+  end
+
+  def recorder
+    @recorder ||= ActiveRecord::QueryRecorder.new(&@subject_block)
+  end
+
+  def count_queries(queries)
+    queries.each_with_object(Hash.new(0)) { |query, counts| counts[query] += 1 }
+  end
+
+  def log_message
+    if expected.is_a?(ActiveRecord::QueryRecorder)
+      counts = count_queries(expected.log)
+      extra_queries = @recorder.log.reject { |query| counts[query] -= 1 unless counts[query].zero? }
+      extra_queries_display = count_queries(extra_queries).map { |query, count| "[#{count}] #{query}" }
+
+      (['Extra queries:'] + extra_queries_display).join("\n\n")
+    else
+      @recorder.log_message
+    end
+  end
+end