Added specs and source documentation for Sherlock

lib/gitlab/sherlock/collection.rb

 module Gitlab
   module Sherlock
+    # A collection of transactions recorded by Sherlock.
+    #
+    # Method calls for this class are synchronized using a mutex to allow
+    # sharing of a single Collection instance between threads (e.g. when using
+    # Puma as a webserver).
     class Collection
       include Enumerable
 
@@ -34,6 +39,8 @@ module Gitlab
         sort { |a, b| b.finished_at <=> a.finished_at }
       end
 
+      private
+
       def synchronize(&block)
         @mutex.synchronize(&block)
       end

lib/gitlab/sherlock/file_sample.rb

@@ -3,6 +3,10 @@ module Gitlab
     class FileSample
       attr_reader :id, :file, :line_samples, :events, :duration
 
+      # file - The full path to the file this sample belongs to.
+      # line_samples - An array of LineSample objects.
+      # duration - The total execution time in milliseconds.
+      # events - The total amount of events.
       def initialize(file, line_samples, duration, events)
         @id = SecureRandom.uuid
         @file = file

lib/gitlab/sherlock/line_profiler.rb

 module Gitlab
   module Sherlock
+    # Class for profiling code on a per line basis.
+    #
+    # The LineProfiler class can be used to profile code on per line basis
+    # without littering your code with Ruby implementation specific profiling
+    # methods.
+    #
+    # This profiler only includes samples taking longer than a given threshold
+    # and those that occur in the actual application (e.g. files from Gems are
+    # ignored).
     class LineProfiler
       # The minimum amount of time that has to be spent in a file for it to be
       # included in a list of samples.
       MINIMUM_DURATION = 10.0
 
+      # Profiles the given block.
+      #
+      # Example:
+      #
+      #     profiler = LineProfiler.new
+      #
+      #     retval, samples = profiler.profile do
+      #       "cats are amazing"
+      #     end
+      #
+      #     retval  # => "cats are amazing"
+      #     samples # => [#<Gitlab::Sherlock::FileSample ...>, ...]
+      #
+      # Returns an Array containing the block's return value and an Array of
+      # FileSample objects.
       def profile(&block)
-        if RUBY_ENGINE == 'ruby'
+        if mri?
           profile_mri(&block)
         else
           raise NotImplementedError,
@@ -14,6 +38,7 @@ module Gitlab
         end
       end
 
+      # Profiles the given block using rblineprof (MRI only).
       def profile_mri
         retval  = nil
         samples = lineprof(/^#{Rails.root.to_s}/) { retval = yield }
@@ -24,6 +49,11 @@ module Gitlab
       end
 
       # Returns an Array of file samples based on the output of rblineprof.
+      #
+      # lineprof_stats - A Hash containing rblineprof statistics on a per file
+      #                  basis.
+      #
+      # Returns an Array of FileSample objects.
       def aggregate_rblineprof(lineprof_stats)
         samples = []
 
@@ -52,9 +82,15 @@ module Gitlab
         samples
       end
 
+      private
+
       def microsec_to_millisec(microsec)
         microsec / 1000.0
       end
+
+      def mri?
+        RUBY_ENGINE == 'ruby'
+      end
     end
   end
 end

lib/gitlab/sherlock/line_sample.rb

@@ -3,15 +3,31 @@ module Gitlab
     class LineSample
       attr_reader :duration, :events
 
+      # duration - The execution time in milliseconds.
+      # events - The amount of events.
       def initialize(duration, events)
         @duration = duration
         @events = events
       end
 
+      # Returns the sample duration percentage relative to the given duration.
+      #
+      # Example:
+      #
+      #     sample.duration            # => 150
+      #     sample.percentage_of(1500) # => 10.0
+      #
+      # total_duration - The total duration to compare with.
+      #
+      # Returns a float
       def percentage_of(total_duration)
         (duration.to_f / total_duration) * 100.0
       end
 
+      # Returns true if the current sample takes up the majority of the given
+      # duration.
+      #
+      # total_duration - The total duration to compare with.
       def majority_of?(total_duration)
         percentage_of(total_duration) >= 30
       end

lib/gitlab/sherlock/location.rb

@@ -5,15 +5,19 @@ module Gitlab
 
       SHERLOCK_DIR = File.dirname(__FILE__)
 
+      # Creates a new Location from a `Thread::Backtrace::Location`.
       def self.from_ruby_location(location)
         new(location.path, location.lineno)
       end
 
+      # path - The full path of the frame as a String.
+      # line - The line number of the frame as a Fixnum.
       def initialize(path, line)
         @path = path
         @line = line
       end
 
+      # Returns true if the current frame originated from the application.
       def application?
         @path.start_with?(Rails.root.to_s) && !path.start_with?(SHERLOCK_DIR)
       end

lib/gitlab/sherlock/middleware.rb

@@ -10,6 +10,7 @@ module Gitlab
         @app = app
       end
 
+      # env - A Hash containing Rack environment details.
       def call(env)
         if instrument?(env)
           call_with_instrumentation(env)
@@ -19,7 +20,7 @@ module Gitlab
       end
 
       def call_with_instrumentation(env)
-        trans = Transaction.new(env['REQUEST_METHOD'], env['REQUEST_URI'])
+        trans = transaction_from_env(env)
         retval = trans.run { @app.call(env) }
 
         Sherlock.collection.add(trans)
@@ -31,6 +32,10 @@ module Gitlab
         !!(env['HTTP_ACCEPT'] =~ CONTENT_TYPES &&
            env['REQUEST_URI'] !~ IGNORE_PATHS)
       end
+
+      def transaction_from_env(env)
+        Transaction.new(env['REQUEST_METHOD'], env['REQUEST_URI'])
+      end
     end
   end
 end

lib/gitlab/sherlock/query.rb

@@ -3,6 +3,7 @@ module Gitlab
     class Query
       attr_reader :id, :query, :started_at, :finished_at, :backtrace
 
+      # SQL identifiers that should be prefixed with newlines.
       PREFIX_NEWLINE = /
         \s+(FROM
           |(LEFT|RIGHT)?INNER\s+JOIN
@@ -12,11 +13,20 @@ module Gitlab
           |GROUP\s+BY
           |ORDER\s+BY
           |LIMIT
-          |OFFSET)\s+
-      /ix
-
+          |OFFSET)\s+/ix # Vim indent breaks when this is on a newline :<
+
+      # Creates a new Query using a String and a separate Array of bindings.
+      #
+      # query - A String containing a SQL query, optionally with numeric
+      #         placeholders (`$1`, `$2`, etc).
+      #
+      # bindings - An Array of ActiveRecord columns and their values.
+      # started_at - The start time of the query as a Time-like object.
+      # finished_at - The completion time of the query as a Time-like object.
+      #
+      # Returns a new Query object.
       def self.new_with_bindings(query, bindings, started_at, finished_at)
-        bindings.each_with_index do |(column, value), index|
+        bindings.each_with_index do |(_, value), index|
           quoted_value = ActiveRecord::Base.connection.quote(value)
 
           query = query.gsub("$#{index + 1}", quoted_value)
@@ -25,6 +35,9 @@ module Gitlab
         new(query, started_at, finished_at)
       end
 
+      # query - The SQL query as a String (without placeholders).
+      # started_at - The start time of the query as a Time-like object.
+      # finished_at - The completion time of the query as a Time-like object.
       def initialize(query, started_at, finished_at)
         @id = SecureRandom.uuid
         @query = query
@@ -39,6 +52,7 @@ module Gitlab
         end
       end
 
+      # Returns the query duration in milliseconds.
       def duration
         @duration ||= (@finished_at - @started_at) * 1000.0
       end
@@ -47,18 +61,22 @@ module Gitlab
         @id
       end
 
+      # Returns a human readable version of the query.
       def formatted_query
         @formatted_query ||= format_sql(@query)
       end
 
+      # Returns the last application frame of the backtrace.
       def last_application_frame
         @last_application_frame ||= @backtrace.find(&:application?)
       end
 
+      # Returns an Array of application frames (excluding Gems and the likes).
       def application_backtrace
         @application_backtrace ||= @backtrace.select(&:application?)
       end
 
+      # Returns the query plan as a String.
       def explain
         unless @explain
           ActiveRecord::Base.connection.transaction do

lib/gitlab/sherlock/transaction.rb

@@ -4,11 +4,12 @@ module Gitlab
       attr_reader :id, :type, :path, :queries, :file_samples, :started_at,
         :finished_at
 
+      # type - The type of transaction (e.g. "GET", "POST", etc)
+      # path - The path of the transaction (e.g. the HTTP request path)
       def initialize(type, path)
         @id = SecureRandom.uuid
         @type = type
         @path = path
-        @duration = 0
         @queries = []
         @file_samples = []
         @started_at = nil
@@ -16,6 +17,7 @@ module Gitlab
         @thread = Thread.current
       end
 
+      # Runs the transaction and returns the block's return value.
       def run
         @started_at = Time.now
 
@@ -30,34 +32,43 @@ module Gitlab
         retval
       end
 
+      # Returns the duration in seconds.
       def duration
-        @started_at && @finished_at ? @finished_at - @started_at : 0
+        @duration ||= started_at && finished_at ? finished_at - started_at : 0
       end
 
       def to_param
         @id
       end
 
+      # Returns the queries sorted in descending order by their durations.
       def sorted_queries
         @queries.sort { |a, b| b.duration <=> a.duration }
       end
 
+      # Returns the file samples sorted in descending order by their durations.
       def sorted_file_samples
         @file_samples.sort { |a, b| b.duration <=> a.duration }
       end
 
+      # Finds a query by the given ID.
+      #
+      # id - The query ID as a String.
+      #
+      # Returns a Query object if one could be found, nil otherwise.
       def find_query(id)
         @queries.find { |query| query.id == id }
       end
 
+      # Finds a file sample by the given ID.
+      #
+      # id - The query ID as a String.
+      #
+      # Returns a FileSample object if one could be found, nil otherwise.
       def find_file_sample(id)
         @file_samples.find { |sample| sample.id == id }
       end
 
-      def track_query(query, bindings, start, finish)
-        @queries << Query.new_with_bindings(query, bindings, start, finish)
-      end
-
       def profile_lines
         retval = nil
 
@@ -70,6 +81,12 @@ module Gitlab
         retval
       end
 
+      private
+
+      def track_query(query, bindings, start, finish)
+        @queries << Query.new_with_bindings(query, bindings, start, finish)
+      end
+
       def subscribe_to_active_record
         ActiveSupport::Notifications.subscribe('sql.active_record') do |_, start, finish, _, data|
           # In case somebody uses a multi-threaded server locally (e.g. Puma) we

spec/lib/gitlab/sherlock/collection_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Sherlock::Collection do
+  let(:collection) { described_class.new }
+
+  let(:transaction) do
+    Gitlab::Sherlock::Transaction.new('POST', '/cat_pictures')
+  end
+
+  describe '#add' do
+    it 'adds a new transaction' do
+      collection.add(transaction)
+
+      expect(collection).to_not be_empty
+    end
+
+    it 'is aliased as <<' do
+      collection << transaction
+
+      expect(collection).to_not be_empty
+    end
+  end
+
+  describe '#each' do
+    it 'iterates over every transaction' do
+      collection.add(transaction)
+
+      expect { |b| collection.each(&b) }.to yield_with_args(transaction)
+    end
+  end
+
+  describe '#clear' do
+    it 'removes all transactions' do
+      collection.add(transaction)
+
+      collection.clear
+
+      expect(collection).to be_empty
+    end
+  end
+
+  describe '#empty?' do
+    it 'returns true for an empty collection' do
+      expect(collection).to be_empty
+    end
+
+    it 'returns false for a collection with a transaction' do
+      collection.add(transaction)
+
+      expect(collection).to_not be_empty
+    end
+  end
+
+  describe '#find_transaction' do
+    it 'returns the transaction for the given ID' do
+      collection.add(transaction)
+
+      expect(collection.find_transaction(transaction.id)).to eq(transaction)
+    end
+
+    it 'returns nil when no transaction could be found' do
+      collection.add(transaction)
+
+      expect(collection.find_transaction('cats')).to be_nil
+    end
+  end
+
+  describe '#newest_first' do
+    it 'returns transactions sorted from new to old' do
+      trans1 = Gitlab::Sherlock::Transaction.new('POST', '/cat_pictures')
+      trans2 = Gitlab::Sherlock::Transaction.new('POST', '/more_cat_pictures')
+
+      allow(trans1).to receive(:finished_at).and_return(Time.utc(2015, 1, 1))
+      allow(trans2).to receive(:finished_at).and_return(Time.utc(2015, 1, 2))
+
+      collection.add(trans1)
+      collection.add(trans2)
+
+      expect(collection.newest_first).to eq([trans2, trans1])
+    end
+  end
+end

spec/lib/gitlab/sherlock/file_sample_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Sherlock::FileSample do
+  let(:sample) { described_class.new(__FILE__, [], 150.4, 2) }
+
+  describe '#id' do
+    it 'returns the ID' do
+      expect(sample.id).to be_an_instance_of(String)
+    end
+  end
+
+  describe '#file' do
+    it 'returns the file path' do
+      expect(sample.file).to eq(__FILE__)
+    end
+  end
+
+  describe '#line_samples' do
+    it 'returns the line samples' do
+      expect(sample.line_samples).to eq([])
+    end
+  end
+
+  describe '#events' do
+    it 'returns the total number of events' do
+      expect(sample.events).to eq(2)
+    end
+  end
+
+  describe '#duration' do
+    it 'returns the total execution time' do
+      expect(sample.duration).to eq(150.4)
+    end
+  end
+
+  describe '#relative_path' do
+    it 'returns the relative path' do
+      expect(sample.relative_path).
+        to eq('spec/lib/gitlab/sherlock/file_sample_spec.rb')
+    end
+  end
+
+  describe '#to_param' do
+    it 'returns the sample ID' do
+      expect(sample.to_param).to eq(sample.id)
+    end
+  end
+
+  describe '#source' do
+    it 'returns the contents of the file' do
+      expect(sample.source).to eq(File.read(__FILE__))
+    end
+  end
+end

spec/lib/gitlab/sherlock/line_profiler_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Sherlock::LineProfiler do
+  let(:profiler) { described_class.new }
+
+  describe '#profile' do
+    it 'runs the profiler when using MRI' do
+      allow(profiler).to receive(:mri?).and_return(true)
+      allow(profiler).to receive(:profile_mri)
+
+      profiler.profile { 'cats' }
+    end
+
+    it 'raises NotImplementedError when profiling an unsupported platform' do
+      allow(profiler).to receive(:mri?).and_return(false)
+
+      expect { profiler.profile { 'cats' } }.to raise_error(NotImplementedError)
+    end
+  end
+
+  describe '#profile_mri' do
+    it 'returns an Array containing the return value and profiling samples' do
+      allow(profiler).to receive(:lineprof).
+        and_yield.
+        and_return({ __FILE__ => [[0, 0, 0, 0]] })
+
+      retval, samples = profiler.profile_mri { 42 }
+
+      expect(retval).to eq(42)
+      expect(samples).to eq([])
+    end
+  end
+
+  describe '#aggregate_rblineprof' do
+    let(:raw_samples) do
+      { __FILE__ => [[30000, 30000, 5, 0], [15000, 15000, 4, 0]] }
+    end
+
+    it 'returns an Array of FileSample objects' do
+      samples = profiler.aggregate_rblineprof(raw_samples)
+
+      expect(samples).to be_an_instance_of(Array)
+      expect(samples[0]).to be_an_instance_of(Gitlab::Sherlock::FileSample)
+    end
+
+    describe 'the first FileSample object' do
+      let(:file_sample) do
+        profiler.aggregate_rblineprof(raw_samples)[0]
+      end
+
+      it 'uses the correct file path' do
+        expect(file_sample.file).to eq(__FILE__)
+      end
+
+      it 'contains a list of line samples' do
+        line_sample = file_sample.line_samples[0]
+
+        expect(line_sample).to be_an_instance_of(Gitlab::Sherlock::LineSample)
+
+        expect(line_sample.duration).to eq(15.0)
+        expect(line_sample.events).to eq(4)
+      end
+
+      it 'contains the total file execution time' do
+        expect(file_sample.duration).to eq(30.0)
+      end
+
+      it 'contains the total amount of file events' do
+        expect(file_sample.events).to eq(5)
+      end
+    end
+  end
+end

spec/lib/gitlab/sherlock/line_sample_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Sherlock::LineSample do
+  let(:sample) { described_class.new(150.0, 4) }
+
+  describe '#duration' do
+    it 'returns the duration' do
+      expect(sample.duration).to eq(150.0)
+    end
+  end
+
+  describe '#events' do
+    it 'returns the amount of events' do
+      expect(sample.events).to eq(4)
+    end
+  end
+
+  describe '#percentage_of' do
+    it 'returns the percentage of 1500.0' do
+      expect(sample.percentage_of(1500.0)).to be_within(0.1).of(10.0)
+    end
+  end
+
+  describe '#majority_of' do
+    it 'returns true if the sample takes up the majority of the given duration' do
+      expect(sample.majority_of?(500.0)).to eq(true)
+    end
+
+    it "returns false if the sample doesn't take up the majority of the given duration" do
+      expect(sample.majority_of?(1500.0)).to eq(false)
+    end
+  end
+end

spec/lib/gitlab/sherlock/location_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Sherlock::Location do
+  let(:location) { described_class.new(__FILE__, 1) }
+
+  describe 'from_ruby_location' do
+    it 'creates a Location from a Thread::Backtrace::Location' do
+      input  = caller_locations[0]
+      output = described_class.from_ruby_location(input)
+
+      expect(output).to be_an_instance_of(described_class)
+      expect(output.path).to eq(input.path)
+      expect(output.line).to eq(input.lineno)
+    end
+  end
+
+  describe '#path' do
+    it 'returns the file path' do
+      expect(location.path).to eq(__FILE__)
+    end
+  end
+
+  describe '#line' do
+    it 'returns the line number' do
+      expect(location.line).to eq(1)
+    end
+  end
+
+  describe '#application?' do
+    it 'returns true for an application frame' do
+      expect(location.application?).to eq(true)
+    end
+
+    it 'returns false for a non application frame' do
+      loc = described_class.new('/tmp/cats.rb', 1)
+
+      expect(loc.application?).to eq(false)
+    end
+  end
+end

spec/lib/gitlab/sherlock/middleware_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Sherlock::Middleware do
+  let(:app) { double(:app) }
+  let(:middleware) { described_class.new(app) }
+
+  describe '#call' do
+    describe 'when instrumentation is enabled' do
+      it 'instruments a request' do
+        allow(middleware).to receive(:instrument?).and_return(true)
+        allow(middleware).to receive(:call_with_instrumentation)
+
+        middleware.call({})
+      end
+    end
+
+    describe 'when instrumentation is disabled' do
+      it "doesn't instrument a request" do
+        allow(middleware).to receive(:instrument).and_return(false)
+        allow(app).to receive(:call)
+
+        middleware.call({})
+      end
+    end
+  end
+
+  describe '#call_with_instrumentation' do
+    it 'instruments a request' do
+      trans = double(:transaction)
+      retval = 'cats are amazing'
+      env = {}
+
+      allow(app).to receive(:call).with(env).and_return(retval)
+      allow(middleware).to receive(:transaction_from_env).and_return(trans)
+      allow(trans).to receive(:run).and_yield.and_return(retval)
+      allow(Gitlab::Sherlock.collection).to receive(:add).with(trans)
+
+      middleware.call_with_instrumentation(env)
+    end
+  end
+
+  describe '#instrument?' do
+    it 'returns false for a text/css request' do
+      env = { 'HTTP_ACCEPT' => 'text/css', 'REQUEST_URI' => '/' }
+
+      expect(middleware.instrument?(env)).to eq(false)
+    end
+
+    it 'returns false for a request to a Sherlock route' do
+      env = {
+        'HTTP_ACCEPT' => 'text/html',
+        'REQUEST_URI' => '/sherlock/transactions'
+      }
+
+      expect(middleware.instrument?(env)).to eq(false)
+    end
+
+    it 'returns true for a request that should be instrumented' do
+      env = {
+        'HTTP_ACCEPT' => 'text/html',
+        'REQUEST_URI' => '/cats'
+      }
+
+      expect(middleware.instrument?(env)).to eq(true)
+    end
+  end
+
+  describe '#transaction_from_env' do
+    it 'returns a Transaction' do
+      env = {
+        'HTTP_ACCEPT' => 'text/html',
+        'REQUEST_URI' => '/cats'
+      }
+
+      expect(middleware.transaction_from_env(env)).
+        to be_an_instance_of(Gitlab::Sherlock::Transaction)
+    end
+  end
+end

spec/lib/gitlab/sherlock/query_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Sherlock::Query do
+  let(:started_at)  { Time.utc(2015, 1, 1) }
+  let(:finished_at) { started_at + 5 }
+
+  let(:query) do
+    described_class.new('SELECT COUNT(*) FROM users', started_at, finished_at)
+  end
+
+  describe 'new_with_bindings' do
+    it 'returns a Query' do
+      sql = 'SELECT COUNT(*) FROM users WHERE id = $1'
+      bindings = [[double(:column), 10]]
+
+      query = described_class.
+        new_with_bindings(sql, bindings, started_at, finished_at)
+
+      expect(query.query).to eq('SELECT COUNT(*) FROM users WHERE id = 10;')
+    end
+  end
+
+  describe '#id' do
+    it 'returns a String' do
+      expect(query.id).to be_an_instance_of(String)
+    end
+  end
+
+  describe '#query' do
+    it 'returns the query with a trailing semi-colon' do
+      expect(query.query).to eq('SELECT COUNT(*) FROM users;')
+    end
+  end
+
+  describe '#started_at' do
+    it 'returns the start time' do
+      expect(query.started_at).to eq(started_at)
+    end
+  end
+
+  describe '#finished_at' do
+    it 'returns the completion time' do
+      expect(query.finished_at).to eq(finished_at)
+    end
+  end
+
+  describe '#backtrace' do
+    it 'returns the backtrace' do
+      expect(query.backtrace).to be_an_instance_of(Array)
+    end
+  end
+
+  describe '#duration' do
+    it 'returns the duration in milliseconds' do
+      expect(query.duration).to be_within(0.1).of(5000.0)
+    end
+  end
+
+  describe '#to_param' do
+    it 'returns the query ID' do
+      expect(query.to_param).to eq(query.id)
+    end
+  end
+
+  describe '#formatted_query' do
+    it 'returns a formatted version of the query' do
+      expect(query.formatted_query).to eq(<<-EOF.strip)
+SELECT COUNT(*)
+FROM users;
+      EOF
+    end
+  end
+
+  describe '#last_application_frame' do
+    it 'returns the last application frame' do
+      frame = query.last_application_frame
+
+      expect(frame).to be_an_instance_of(Gitlab::Sherlock::Location)
+      expect(frame.path).to eq(__FILE__)
+    end
+  end
+
+  describe '#application_backtrace' do
+    it 'returns an Array of application frames' do
+      frames = query.application_backtrace
+
+      expect(frames).to be_an_instance_of(Array)
+      expect(frames).to_not be_empty
+
+      frames.each do |frame|
+        expect(frame.path).to start_with(Rails.root.to_s)
+      end
+    end
+  end
+
+  describe '#explain' do
+    it 'returns the query plan as a String' do
+      lines = [
+        ['Aggregate (cost=123 rows=1)'],
+        ['  -> Index Only Scan using index_cats_are_amazing']
+      ]
+
+      result = double(:result, :values => lines)
+
+      allow(query).to receive(:raw_explain).and_return(result)
+
+      expect(query.explain).to eq(<<-EOF.strip)
+Aggregate (cost=123 rows=1)
+  -> Index Only Scan using index_cats_are_amazing
+      EOF
+    end
+  end
+end

spec/lib/gitlab/sherlock/transaction_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Sherlock::Transaction do
+  let(:transaction) { described_class.new('POST', '/cat_pictures') }
+
+  describe '#id' do
+    it 'returns the transaction ID' do
+      expect(transaction.id).to be_an_instance_of(String)
+    end
+  end
+
+  describe '#type' do
+    it 'returns the type' do
+      expect(transaction.type).to eq('POST')
+    end
+  end
+
+  describe '#path' do
+    it 'returns the path' do
+      expect(transaction.path).to eq('/cat_pictures')
+    end
+  end
+
+  describe '#queries' do
+    it 'returns an Array of queries' do
+      expect(transaction.queries).to be_an_instance_of(Array)
+    end
+  end
+
+  describe '#file_samples' do
+    it 'returns an Array of file samples' do
+      expect(transaction.file_samples).to be_an_instance_of(Array)
+    end
+  end
+
+  describe '#started_at' do
+    it 'returns the start time' do
+      allow(transaction).to receive(:profile_lines).and_yield
+
+      transaction.run { 'cats are amazing' }
+
+      expect(transaction.started_at).to be_an_instance_of(Time)
+    end
+  end
+
+  describe '#finished_at' do
+    it 'returns the completion time' do
+      allow(transaction).to receive(:profile_lines).and_yield
+
+      transaction.run { 'cats are amazing' }
+
+      expect(transaction.finished_at).to be_an_instance_of(Time)
+    end
+  end
+
+  describe '#run' do
+    it 'runs the transaction' do
+      allow(transaction).to receive(:profile_lines).and_yield
+
+      retval = transaction.run { 'cats are amazing' }
+
+      expect(retval).to eq('cats are amazing')
+    end
+  end
+
+  describe '#duration' do
+    it 'returns the duration in seconds' do
+      start_time = Time.now
+
+      allow(transaction).to receive(:started_at).and_return(start_time)
+      allow(transaction).to receive(:finished_at).and_return(start_time + 5)
+
+      expect(transaction.duration).to be_within(0.1).of(5.0)
+    end
+  end
+
+  describe '#to_param' do
+    it 'returns the transaction ID' do
+      expect(transaction.to_param).to eq(transaction.id)
+    end
+  end
+
+  describe '#sorted_queries' do
+    it 'returns the queries in descending order' do
+      start_time = Time.now
+
+      query1 = Gitlab::Sherlock::Query.new('SELECT 1', start_time, start_time)
+
+      query2 = Gitlab::Sherlock::Query.
+        new('SELECT 2', start_time, start_time + 5)
+
+      transaction.queries << query1
+      transaction.queries << query2
+
+      expect(transaction.sorted_queries).to eq([query2, query1])
+    end
+  end
+
+  describe '#sorted_file_samples' do
+    it 'returns the file samples in descending order' do
+      sample1 = Gitlab::Sherlock::FileSample.new(__FILE__, [], 10.0, 1)
+      sample2 = Gitlab::Sherlock::FileSample.new(__FILE__, [], 15.0, 1)
+
+      transaction.file_samples << sample1
+      transaction.file_samples << sample2
+
+      expect(transaction.sorted_file_samples).to eq([sample2, sample1])
+    end
+  end
+
+  describe '#find_query' do
+    it 'returns a Query when found' do
+      query = Gitlab::Sherlock::Query.new('SELECT 1', Time.now, Time.now)
+
+      transaction.queries << query
+
+      expect(transaction.find_query(query.id)).to eq(query)
+    end
+
+    it 'returns nil when no query could be found' do
+      expect(transaction.find_query('cats')).to be_nil
+    end
+  end
+
+  describe '#find_file_sample' do
+    it 'returns a FileSample when found' do
+      sample = Gitlab::Sherlock::FileSample.new(__FILE__, [], 10.0, 1)
+
+      transaction.file_samples << sample
+
+      expect(transaction.find_file_sample(sample.id)).to eq(sample)
+    end
+
+    it 'returns nil when no file sample could be found' do
+      expect(transaction.find_file_sample('cats')).to be_nil
+    end
+  end
+
+  describe '#profile_lines' do
+    describe 'when line profiling is enabled' do
+      it 'yields the block using the line profiler' do
+        allow(Gitlab::Sherlock).to receive(:enable_line_profiler?).
+          and_return(true)
+
+        allow_any_instance_of(Gitlab::Sherlock::LineProfiler).
+          to receive(:profile).and_return('cats are amazing', [])
+
+        retval = transaction.profile_lines { 'cats are amazing' }
+
+        expect(retval).to eq('cats are amazing')
+      end
+    end
+
+    describe 'when line profiling is disabled' do
+      it 'yields the block' do
+        allow(Gitlab::Sherlock).to receive(:enable_line_profiler?).
+          and_return(false)
+
+        retval = transaction.profile_lines { 'cats are amazing' }
+
+        expect(retval).to eq('cats are amazing')
+      end
+    end
+  end
+end