Cover cursor boundary contracts and floating-point round trips

CHANGELOG.md

@@ -1,5 +1,6 @@
 ### 2.0.2 (Next)
 
+* [#53](https://github.com/mongoid/mongoid-scroll/pull/53): Cover float cursor round trips, serialization errors, abstract contracts and descending tiebreaker inclusion - [@dblock](https://github.com/dblock).
 * Your contribution here.
 
 ### 2.0.1 (2026/10/15)

spec/mongoid/scroll/base_cursor_spec.rb

@@ -0,0 +1,38 @@
+require 'spec_helper'
+
+describe Mongoid::Scroll::BaseCursor do
+  it 'requires subclasses to implement serialization' do
+    expect { described_class.new(nil).to_s }.to raise_error(NotImplementedError, /to_s/)
+  end
+
+  it 'requires subclasses to implement parsing' do
+    expect { described_class.new(nil).send(:parse, 'cursor') }.to raise_error(NotImplementedError, /parse/)
+  end
+
+  it 'round trips a floating-point cursor' do
+    id = BSON::ObjectId.new
+    cursor = Mongoid::Scroll::Cursor.from_record({ 'score' => 1.25, '_id' => id }, field_name: 'score', field_type: Float)
+
+    expect(cursor.to_s).to eq("1.25:#{id}")
+    expect(Mongoid::Scroll::Cursor.new(cursor.to_s, field_name: 'score', field_type: Float).value).to eq(1.25)
+  end
+
+  it 'rejects an unsupported field type during serialization' do
+    cursor = Mongoid::Scroll::Cursor.new(nil, field_name: 'values', field_type: Array)
+    cursor.value = [1]
+    cursor.tiebreak_id = BSON::ObjectId.new
+
+    expect { cursor.to_s }.to raise_error(Mongoid::Scroll::Errors::UnsupportedFieldTypeError, /Array/)
+  end
+
+  it 'includes the descending tiebreaker record when requested' do
+    id = BSON::ObjectId.new
+    cursor = described_class.new(3, field_name: 'score', field_type: Integer, direction: -1, include_current: true, tiebreak_id: id)
+
+    expected = [
+      { 'score' => { '$lt' => 3 } },
+      { 'score' => 3, '_id' => { '$lte' => id } }
+    ]
+    expect(cursor.criteria).to eq('$or' => expected)
+  end
+end

spec/mongoid/scroll_version_spec.rb

@@ -0,0 +1,7 @@
+require 'spec_helper'
+
+describe Mongoid::Scroll do
+  it 'defines a semantic version' do
+    expect(Mongoid::Scroll::VERSION).to match(/\A\d+\.\d+\.\d+\z/)
+  end
+end