1 files changed, 54 insertions, 0 deletions
diff --git a/spec/services/ci/prepare_build_service_spec.rb b/spec/services/ci/prepare_build_service_spec.rb
new file mode 100644
index 00000000000..1797f8f964f
--- /dev/null
+++ b/spec/services/ci/prepare_build_service_spec.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Ci::PrepareBuildService do
+  describe '#execute' do
+    let(:build) { create(:ci_build, :preparing) }
+
+    subject { described_class.new(build).execute }
+
+    before do
+      allow(build).to receive(:prerequisites).and_return(prerequisites)
+    end
+
+    shared_examples 'build enqueueing' do
+      it 'enqueues the build' do
+        expect(build).to receive(:enqueue).once
+
+        subject
+      end
+    end
+
+    context 'build has unmet prerequisites' do
+      let(:prerequisite) { double(complete!: true) }
+      let(:prerequisites) { [prerequisite] }
+
+      it 'completes each prerequisite' do
+        expect(prerequisites).to all(receive(:complete!))
+
+        subject
+      end
+
+      include_examples 'build enqueueing'
+
+      context 'prerequisites fail to complete' do
+        before do
+          allow(build).to receive(:enqueue).and_return(false)
+        end
+
+        it 'drops the build' do
+          expect(build).to receive(:drop!).with(:unmet_prerequisites).once
+
+          subject
+        end
+      end
+    end
+
+    context 'build has no prerequisites' do
+      let(:prerequisites) { [] }
+
+      include_examples 'build enqueueing'
+    end
+  end
+end