document and test Hyrax::LeaseManager

`LeaseManager` is substantially similar to `EmbargoManager`, and got in without
tests, with the idea that a refactor might quickly take place. it didn't and at
this point it needs a test harness if that's ever going to happen.

in the meanwhile. there are features we want to add to cover the remainder of
the lifecycle.

app/services/hyrax/lease_manager.rb

@@ -1,6 +1,9 @@
 # frozen_string_literal: true
 
 module Hyrax
+  ##
+  # Provides utilities for managing the lifecycle of an `Hyrax::Lease` on a
+  # `Hyrax::Resource`.
   class LeaseManager
     ##
     # @!attribute [rw] resource
@@ -31,6 +34,12 @@ def lease_for(resource:, query_service: Hyrax.query_service)
       end
     end
 
+    ##
+    # Copies and applies the lease to a new (target) resource.
+    #
+    # @param target [Hyrax::Resource]
+    #
+    # @return [Boolean]
     def copy_lease_to(target:)
       return false unless under_lease?
 
@@ -47,7 +56,14 @@ def apply
     end
 
     ##
-    # @return [Valkyrie::Resource]
+    # @return [void]
+    # @raise [NotEnforcableError] when trying to apply an lease that isn't active
+    def apply!
+      apply || raise(NotEnforcableError)
+    end
+
+    ##
+    # @return [Hyrax::Lease]
     def lease
       resource.lease || Lease.new
     end
@@ -58,6 +74,9 @@ def under_lease?
       lease.active?
     end
 
+    class NotEnforcableError < RuntimeError; end
+    class NotReleasableError < RuntimeError; end
+
     private
 
       def clone_attributes

spec/services/hyrax/lease_manager_spec.rb

@@ -0,0 +1,84 @@
+# frozen_string_literal: true
+
+RSpec.describe Hyrax::LeaseManager do
+  subject(:manager) { described_class.new(resource: resource) }
+  let(:resource)    { Hyrax::Resource.new }
+
+  shared_context 'when under lease' do
+    let(:resource) { FactoryBot.build(:hyrax_resource, :under_lease) }
+  end
+
+  shared_context 'with expired lease' do
+    let(:resource) { FactoryBot.build(:hyrax_resource, lease: lease) }
+    let(:lease)  { FactoryBot.build(:hyrax_lease, :expired) }
+  end
+
+  describe '#apply' do
+    context 'with no lease' do
+      it 'is a no-op' do
+        expect { manager.apply }
+          .not_to change { resource.visibility }
+      end
+    end
+
+    context 'with expired lease' do
+      include_context 'with expired lease'
+
+      it 'is a no-op' do
+        expect { manager.apply }
+          .not_to change { resource.visibility }
+      end
+    end
+
+    context 'when under lease' do
+      include_context 'when under lease'
+
+      before { resource.visibility = 'restricted' }
+
+      it 'applies the active lease visibility' do
+        expect { manager.apply }
+          .to change { resource.visibility }
+          .from('restricted')
+          .to 'open'
+      end
+    end
+  end
+
+  describe '#lease' do
+    it 'gives an inactive lease' do
+      expect(manager.lease).not_to be_active
+    end
+
+    context 'when under lease' do
+      include_context 'when under lease'
+
+      it 'gives an active lease' do
+        expect(manager.lease).to be_active
+      end
+
+      it 'has lease attributes' do
+        expect(manager.lease)
+          .to have_attributes visibility_after_lease: 'authenticated',
+                              visibility_during_lease: 'open',
+                              lease_expiration_date: an_instance_of(Date),
+                              lease_history: be_empty
+      end
+    end
+  end
+
+  describe '#under_lease?' do
+    it { is_expected.not_to be_under_lease }
+
+    context 'when under lease' do
+      include_context 'when under lease'
+
+      it { is_expected.to be_under_lease }
+    end
+
+    context 'with expired lease' do
+      include_context 'with expired lease'
+
+      it { is_expected.not_to be_under_lease }
+    end
+  end
+end