diff --git a/spec/shared_print/phase_updater_spec.rb b/spec/shared_print/phase_updater_spec.rb
new file mode 100644
index 00000000..6920aeab
--- /dev/null
+++ b/spec/shared_print/phase_updater_spec.rb
@@ -0,0 +1,42 @@
+require "cluster"
+require "shared_print/finder"
+require "shared_print/phase_updater"
+require "shared_print/phases"
+
+RSpec.describe SharedPrint::PhaseUpdater do
+  before(:each) do
+    Cluster.collection.find.delete_many
+  end
+  it "updates `phase` on commitments based on `committed_date`" do
+    # Make 5 commitments with a known committed_date
+    # and a phase that needs updating.
+    clusterables = []
+    1.upto(5) do |i|
+      clusterables << build(
+        :commitment,
+        ocn: i,
+        phase: SharedPrint::Phases::PHASE_0,
+        committed_date: SharedPrint::Phases::PHASE_1_DATE
+      )
+    end
+    cluster_tap_save(*clusterables)
+    # Verify that we loaded what we think we loaded:
+    # 5 commitments with the same phase and the same date.
+    original_commitments = SharedPrint::Finder.new(phase: [0]).commitments.to_a
+    expect(original_commitments.count).to eq 5
+    expect(original_commitments.map(&:phase).uniq).to eq [SharedPrint::Phases::PHASE_0]
+    expect(original_commitments.map(&:committed_date).uniq).to eq [SharedPrint::Phases::PHASE_1_DATE]
+
+    # Here we want to update to phase 1, to match the phase 1 date.
+    phase_updater = described_class.new(
+      SharedPrint::Phases::PHASE_1_DATE,
+      SharedPrint::Phases::PHASE_1
+    )
+    phase_updater.run
+    # Verify that the commitments now have phase 1.
+    updated_commitments = SharedPrint::Finder.new(phase: [1]).commitments.to_a
+    expect(updated_commitments.count).to eq 5
+    expect(updated_commitments.map(&:phase).uniq).to eq [SharedPrint::Phases::PHASE_1]
+    expect(updated_commitments.map(&:committed_date).uniq).to eq [SharedPrint::Phases::PHASE_1_DATE]
+  end
+end