diff --git a/config/initializers/metrics.rb b/config/initializers/metrics.rb
index 3b8771543e4..e0702e06cc9 100644
--- a/config/initializers/metrics.rb
+++ b/config/initializers/metrics.rb
@@ -1,3 +1,117 @@
+# Autoload all classes that we want to instrument, and instrument the methods we
+# need. This takes the Gitlab::Metrics::Instrumentation module as an argument so
+# that we can stub it for testing, as it is only called when metrics are
+# enabled.
+#
+# rubocop:disable Metrics/AbcSize
+def instrument_classes(instrumentation)
+  instrumentation.instrument_instance_methods(Gitlab::Shell)
+
+  instrumentation.instrument_methods(Gitlab::Git)
+
+  Gitlab::Git.constants.each do |name|
+    const = Gitlab::Git.const_get(name)
+
+    next unless const.is_a?(Module)
+
+    instrumentation.instrument_methods(const)
+    instrumentation.instrument_instance_methods(const)
+  end
+
+  # Path to search => prefix to strip from constant
+  paths_to_instrument = {
+    ['app', 'finders']                    => ['app', 'finders'],
+    ['app', 'mailers', 'emails']          => ['app', 'mailers'],
+    ['app', 'services', '**']             => ['app', 'services'],
+    ['lib', 'gitlab', 'conflicts']        => ['lib'],
+    ['lib', 'gitlab', 'diff']             => ['lib'],
+    ['lib', 'gitlab', 'email', 'message'] => ['lib'],
+    ['lib', 'gitlab', 'checks']           => ['lib']
+  }
+
+  paths_to_instrument.each do |(path, prefix)|
+    prefix = Rails.root.join(*prefix)
+
+    Dir[Rails.root.join(*path + ['*.rb'])].each do |file_path|
+      path = Pathname.new(file_path).relative_path_from(prefix)
+      const = path.to_s.sub('.rb', '').camelize.constantize
+
+      instrumentation.instrument_methods(const)
+      instrumentation.instrument_instance_methods(const)
+    end
+  end
+
+  instrumentation.instrument_methods(Premailer::Adapter::Nokogiri)
+  instrumentation.instrument_instance_methods(Premailer::Adapter::Nokogiri)
+
+  [
+    :Blame, :Branch, :BranchCollection, :Blob, :Commit, :Diff, :Repository,
+    :Tag, :TagCollection, :Tree
+  ].each do |name|
+    const = Rugged.const_get(name)
+
+    instrumentation.instrument_methods(const)
+    instrumentation.instrument_instance_methods(const)
+  end
+
+  # Instruments all Banzai filters and reference parsers
+  {
+    Filter: Rails.root.join('lib', 'banzai', 'filter', '*.rb'),
+    ReferenceParser: Rails.root.join('lib', 'banzai', 'reference_parser', '*.rb')
+  }.each do |const_name, path|
+    Dir[path].each do |file|
+      klass = File.basename(file, File.extname(file)).camelize
+      const = Banzai.const_get(const_name).const_get(klass)
+
+      instrumentation.instrument_methods(const)
+      instrumentation.instrument_instance_methods(const)
+    end
+  end
+
+  instrumentation.instrument_methods(Banzai::Renderer)
+  instrumentation.instrument_methods(Banzai::Querying)
+
+  instrumentation.instrument_instance_methods(Banzai::ObjectRenderer)
+  instrumentation.instrument_instance_methods(Banzai::Redactor)
+  instrumentation.instrument_methods(Banzai::NoteRenderer)
+
+  [Issuable, Mentionable, Participable].each do |klass|
+    instrumentation.instrument_instance_methods(klass)
+    instrumentation.instrument_instance_methods(klass::ClassMethods)
+  end
+
+  instrumentation.instrument_methods(Gitlab::ReferenceExtractor)
+  instrumentation.instrument_instance_methods(Gitlab::ReferenceExtractor)
+
+  # Instrument the classes used for checking if somebody has push access.
+  instrumentation.instrument_instance_methods(Gitlab::GitAccess)
+  instrumentation.instrument_instance_methods(Gitlab::GitAccessWiki)
+
+  instrumentation.instrument_instance_methods(API::Helpers)
+
+  instrumentation.instrument_instance_methods(RepositoryCheck::SingleRepositoryWorker)
+
+  instrumentation.instrument_instance_methods(Rouge::Plugins::Redcarpet)
+  instrumentation.instrument_instance_methods(Rouge::Formatters::HTMLGitlab)
+
+  [:XML, :HTML].each do |namespace|
+    namespace_mod = Nokogiri.const_get(namespace)
+
+    instrumentation.instrument_methods(namespace_mod)
+    instrumentation.instrument_methods(namespace_mod::Document)
+  end
+
+  instrumentation.instrument_methods(Rinku)
+  instrumentation.instrument_instance_methods(Repository)
+
+  instrumentation.instrument_methods(Gitlab::Highlight)
+  instrumentation.instrument_instance_methods(Gitlab::Highlight)
+
+  # This is a Rails scope so we have to instrument it manually.
+  instrumentation.instrument_method(Project, :visible_to_user)
+end
+# rubocop:enable Metrics/AbcSize
+
 if Gitlab::Metrics.enabled?
   require 'pathname'
   require 'influxdb'
@@ -49,110 +163,7 @@ if Gitlab::Metrics.enabled?
   end
 
   Gitlab::Metrics::Instrumentation.configure do |config|
-    config.instrument_instance_methods(Gitlab::Shell)
-
-    config.instrument_methods(Gitlab::Git)
-
-    Gitlab::Git.constants.each do |name|
-      const = Gitlab::Git.const_get(name)
-
-      next unless const.is_a?(Module)
-
-      config.instrument_methods(const)
-      config.instrument_instance_methods(const)
-    end
-
-    # Path to search => prefix to strip from constant
-    paths_to_instrument = {
-      ['app', 'finders']                    => ['app', 'finders'],
-      ['app', 'mailers', 'emails']          => ['app', 'mailers'],
-      ['app', 'services', '**']             => ['app', 'services'],
-      ['lib', 'gitlab', 'conflicts']        => ['lib'],
-      ['lib', 'gitlab', 'diff']             => ['lib'],
-      ['lib', 'gitlab', 'email', 'message'] => ['lib'],
-      ['lib', 'gitlab', 'checks']           => ['lib']
-    }
-
-    paths_to_instrument.each do |(path, prefix)|
-      prefix = Rails.root.join(*prefix)
-
-      Dir[Rails.root.join(*path + ['*.rb'])].each do |file_path|
-        path = Pathname.new(file_path).relative_path_from(prefix)
-        const = path.to_s.sub('.rb', '').camelize.constantize
-
-        config.instrument_methods(const)
-        config.instrument_instance_methods(const)
-      end
-    end
-
-    config.instrument_methods(Premailer::Adapter::Nokogiri)
-    config.instrument_instance_methods(Premailer::Adapter::Nokogiri)
-
-    [
-      :Blame, :Branch, :BranchCollection, :Blob, :Commit, :Diff, :Repository,
-      :Tag, :TagCollection, :Tree
-    ].each do |name|
-      const = Rugged.const_get(name)
-
-      config.instrument_methods(const)
-      config.instrument_instance_methods(const)
-    end
-
-    # Instruments all Banzai filters and reference parsers
-    {
-      Filter: Rails.root.join('lib', 'banzai', 'filter', '*.rb'),
-      ReferenceParser: Rails.root.join('lib', 'banzai', 'reference_parser', '*.rb')
-    }.each do |const_name, path|
-      Dir[path].each do |file|
-        klass = File.basename(file, File.extname(file)).camelize
-        const = Banzai.const_get(const_name).const_get(klass)
-
-        config.instrument_methods(const)
-        config.instrument_instance_methods(const)
-      end
-    end
-
-    config.instrument_methods(Banzai::Renderer)
-    config.instrument_methods(Banzai::Querying)
-
-    config.instrument_instance_methods(Banzai::ObjectRenderer)
-    config.instrument_instance_methods(Banzai::Redactor)
-    config.instrument_methods(Banzai::NoteRenderer)
-
-    [Issuable, Mentionable, Participable].each do |klass|
-      config.instrument_instance_methods(klass)
-      config.instrument_instance_methods(klass::ClassMethods)
-    end
-
-    config.instrument_methods(Gitlab::ReferenceExtractor)
-    config.instrument_instance_methods(Gitlab::ReferenceExtractor)
-
-    # Instrument the classes used for checking if somebody has push access.
-    config.instrument_instance_methods(Gitlab::GitAccess)
-    config.instrument_instance_methods(Gitlab::GitAccessWiki)
-
-    config.instrument_instance_methods(API::Helpers)
-
-    config.instrument_instance_methods(RepositoryCheck::SingleRepositoryWorker)
-
-    config.instrument_instance_methods(Rouge::Plugins::Redcarpet)
-    config.instrument_instance_methods(Rouge::Formatters::HTMLGitlab)
-
-    [:XML, :HTML].each do |namespace|
-      namespace_mod = Nokogiri.const_get(namespace)
-
-      config.instrument_methods(namespace_mod)
-      config.instrument_methods(namespace_mod::Document)
-    end
-
-    config.instrument_methods(Rinku)
-    config.instrument_instance_methods(Repository)
-
-    config.instrument_methods(Gitlab::Highlight)
-    config.instrument_instance_methods(Gitlab::Highlight)
-
-    # This is a Rails scope so we have to instrument it manually.
-    config.instrument_method(Project, :visible_to_user)
+    instrument_classes(config)
   end
 
   GC::Profiler.enable
diff --git a/spec/initializers/metrics_spec.rb b/spec/initializers/metrics_spec.rb
new file mode 100644
index 00000000000..bb595162370
--- /dev/null
+++ b/spec/initializers/metrics_spec.rb
@@ -0,0 +1,16 @@
+require 'spec_helper'
+require_relative '../../config/initializers/metrics'
+
+describe 'instrument_classes', lib: true do
+  let(:config) { double(:config) }
+
+  before do
+    allow(config).to receive(:instrument_method)
+    allow(config).to receive(:instrument_methods)
+    allow(config).to receive(:instrument_instance_methods)
+  end
+
+  it 'can autoload and instrument all files' do
+    expect { instrument_classes(config) }.not_to raise_error
+  end
+end