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