test auto instrumentation for minitest

Rakefile

@@ -58,6 +58,9 @@ TEST_METADATA = {
   "minitest" => {
     "minitest-5" => "✅ 2.7 / ✅ 3.0 / ✅ 3.1 / ✅ 3.2 / ✅ 3.3 / ✅ 3.4 / ✅ jruby"
   },
+  "minitest_auto_instrument" => {
+    "minitest-5" => "✅ 2.7 / ✅ 3.0 / ✅ 3.1 / ✅ 3.2 / ✅ 3.3 / ✅ 3.4 / ✅ jruby"
+  },
   "activesupport" => {
     "activesupport-4" => "✅ 2.7 / ✅ 3.0 / ✅ 3.1 / ✅ 3.2 / ✅ 3.3 / ✅ 3.4 / ✅ jruby",
     "activesupport-5" => "✅ 2.7 / ✅ 3.0 / ✅ 3.1 / ✅ 3.2 / ✅ 3.3 / ✅ 3.4 / ✅ jruby",
@@ -149,6 +152,7 @@ namespace :spec do
     rspec
     minitest
     minitest_shoulda_context
+    minitest_auto_instrument
     activesupport
     ci_queue_minitest
     ci_queue_rspec

spec/datadog/ci/contrib/minitest_auto_instrument/instrumentation_spec.rb

@@ -0,0 +1,38 @@
+RSpec.describe "Minitest auto instrumentation" do
+  include_context "CI mode activated" do
+    let(:integration_name) { :no_instrument }
+  end
+
+  before do
+    require_relative "../../../../../lib/datadog/ci/auto_instrument"
+
+    require "minitest"
+
+    class SomeTest < Minitest::Test
+      def test_pass
+        assert true
+      end
+
+      def test_pass_other
+        assert true
+      end
+    end
+
+    Minitest.run([])
+  end
+
+  it "instruments test session" do
+    expect(test_session_span).not_to be_nil
+    expect(test_module_span).not_to be_nil
+
+    expect(first_test_suite_span).not_to be_nil
+    expect(first_test_suite_span.name).to eq(
+      "SomeTest at spec/datadog/ci/contrib/minitest_auto_instrument/instrumentation_spec.rb"
+    )
+
+    expect(test_spans).to have(2).items
+    expect(test_spans).to have_unique_tag_values_count(:test_session_id, 1)
+    expect(test_spans).to have_unique_tag_values_count(:test_module_id, 1)
+    expect(test_spans).to have_unique_tag_values_count(:test_suite_id, 1)
+  end
+end