diff --git a/lib/cuprum/collections/rspec.rb b/lib/cuprum/collections/rspec.rb
index 838d592..4465f5a 100644
--- a/lib/cuprum/collections/rspec.rb
+++ b/lib/cuprum/collections/rspec.rb
@@ -6,5 +6,6 @@ module Cuprum::Collections
   # Namespace for RSpec contracts, which validate collection implementations.
   module RSpec
     autoload :Contracts, 'cuprum/collections/rspec/contracts'
+    autoload :Fixtures,  'cuprum/collections/rspec/fixtures'
   end
 end
diff --git a/lib/cuprum/collections/rspec/contracts/basic/command_contracts.rb b/lib/cuprum/collections/rspec/contracts/basic/command_contracts.rb
index de3f7d9..bb7f0ff 100644
--- a/lib/cuprum/collections/rspec/contracts/basic/command_contracts.rb
+++ b/lib/cuprum/collections/rspec/contracts/basic/command_contracts.rb
@@ -428,7 +428,7 @@ module WithBasicCommandContextsContract
             Stannum::Constraints::Types::HashWithStringKeys.new
           end
           let(:fixtures_data) do
-            Cuprum::Collections::RSpec::BOOKS_FIXTURES.dup
+            Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup
           end
           let(:query) do
             Cuprum::Collections::Basic::Query.new(mapped_data)
diff --git a/lib/cuprum/collections/rspec/contracts/query_contracts.rb b/lib/cuprum/collections/rspec/contracts/query_contracts.rb
index 4595d19..341de34 100644
--- a/lib/cuprum/collections/rspec/contracts/query_contracts.rb
+++ b/lib/cuprum/collections/rspec/contracts/query_contracts.rb
@@ -11,7 +11,7 @@ module QueryContracts
     module ShouldBeAQuery
       extend RSpec::SleepingKingStudios::Contract
 
-      BOOKS_FIXTURES = Cuprum::Collections::RSpec::BOOKS_FIXTURES
+      BOOKS_FIXTURES = Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES
       private_constant :BOOKS_FIXTURES
 
       OPERATORS = Cuprum::Collections::Queries::Operators
diff --git a/lib/cuprum/collections/rspec/fixtures.rb b/lib/cuprum/collections/rspec/fixtures.rb
index afeb9d8..7fc189b 100644
--- a/lib/cuprum/collections/rspec/fixtures.rb
+++ b/lib/cuprum/collections/rspec/fixtures.rb
@@ -4,86 +4,89 @@
 
 module Cuprum::Collections::RSpec
   # Sample data for validating collection implementations.
-  BOOKS_FIXTURES = [
-    {
-      'id'           => 0,
-      'title'        => 'The Hobbit',
-      'author'       => 'J.R.R. Tolkien',
-      'series'       => nil,
-      'category'     => 'Science Fiction and Fantasy',
-      'published_at' => '1937-09-21'
-    },
-    {
-      'id'           => 1,
-      'title'        => 'The Silmarillion',
-      'author'       => 'J.R.R. Tolkien',
-      'series'       => nil,
-      'category'     => 'Science Fiction and Fantasy',
-      'published_at' => '1977-09-15'
-    },
-    {
-      'id'           => 2,
-      'title'        => 'The Fellowship of the Ring',
-      'author'       => 'J.R.R. Tolkien',
-      'series'       => 'The Lord of the Rings',
-      'category'     => 'Science Fiction and Fantasy',
-      'published_at' => '1954-07-29'
-    },
-    {
-      'id'           => 3,
-      'title'        => 'The Two Towers',
-      'author'       => 'J.R.R. Tolkien',
-      'series'       => 'The Lord of the Rings',
-      'category'     => 'Science Fiction and Fantasy',
-      'published_at' => '1954-11-11'
-    },
-    {
-      'id'           => 4,
-      'title'        => 'The Return of the King',
-      'author'       => 'J.R.R. Tolkien',
-      'series'       => 'The Lord of the Rings',
-      'category'     => 'Science Fiction and Fantasy',
-      'published_at' => '1955-10-20'
-    },
-    {
-      'id'           => 5,
-      'title'        => 'The Word for World is Forest',
-      'author'       => 'Ursula K. LeGuin',
-      'series'       => nil,
-      'category'     => 'Science Fiction and Fantasy',
-      'published_at' => '1972-03-13'
-    },
-    {
-      'id'           => 6,
-      'title'        => 'The Ones Who Walk Away From Omelas',
-      'author'       => 'Ursula K. LeGuin',
-      'series'       => nil,
-      'category'     => 'Science Fiction and Fantasy',
-      'published_at' => '1973-10-01'
-    },
-    {
-      'id'           => 7,
-      'title'        => 'A Wizard of Earthsea',
-      'author'       => 'Ursula K. LeGuin',
-      'series'       => 'Earthsea',
-      'category'     => 'Science Fiction and Fantasy',
-      'published_at' => '1968-11-01'
-    },
-    {
-      'id'           => 8,
-      'title'        => 'The Tombs of Atuan',
-      'author'       => 'Ursula K. LeGuin',
-      'series'       => 'Earthsea',
-      'category'     => 'Science Fiction and Fantasy',
-      'published_at' => '1970-12-01'
-    },
-    {
-      'id'           => 9,
-      'title'        => 'The Farthest Shore',
-      'author'       => 'Ursula K. LeGuin',
-      'series'       => 'Earthsea',
-      'category'     => 'Science Fiction and Fantasy',
-      'published_at' => '1972-09-01'
-    }
-  ].map(&:freeze).freeze
+  module Fixtures
+    # Sample data for Book objects.
+    BOOKS_FIXTURES = [
+      {
+        'id'           => 0,
+        'title'        => 'The Hobbit',
+        'author'       => 'J.R.R. Tolkien',
+        'series'       => nil,
+        'category'     => 'Science Fiction and Fantasy',
+        'published_at' => '1937-09-21'
+      },
+      {
+        'id'           => 1,
+        'title'        => 'The Silmarillion',
+        'author'       => 'J.R.R. Tolkien',
+        'series'       => nil,
+        'category'     => 'Science Fiction and Fantasy',
+        'published_at' => '1977-09-15'
+      },
+      {
+        'id'           => 2,
+        'title'        => 'The Fellowship of the Ring',
+        'author'       => 'J.R.R. Tolkien',
+        'series'       => 'The Lord of the Rings',
+        'category'     => 'Science Fiction and Fantasy',
+        'published_at' => '1954-07-29'
+      },
+      {
+        'id'           => 3,
+        'title'        => 'The Two Towers',
+        'author'       => 'J.R.R. Tolkien',
+        'series'       => 'The Lord of the Rings',
+        'category'     => 'Science Fiction and Fantasy',
+        'published_at' => '1954-11-11'
+      },
+      {
+        'id'           => 4,
+        'title'        => 'The Return of the King',
+        'author'       => 'J.R.R. Tolkien',
+        'series'       => 'The Lord of the Rings',
+        'category'     => 'Science Fiction and Fantasy',
+        'published_at' => '1955-10-20'
+      },
+      {
+        'id'           => 5,
+        'title'        => 'The Word for World is Forest',
+        'author'       => 'Ursula K. LeGuin',
+        'series'       => nil,
+        'category'     => 'Science Fiction and Fantasy',
+        'published_at' => '1972-03-13'
+      },
+      {
+        'id'           => 6,
+        'title'        => 'The Ones Who Walk Away From Omelas',
+        'author'       => 'Ursula K. LeGuin',
+        'series'       => nil,
+        'category'     => 'Science Fiction and Fantasy',
+        'published_at' => '1973-10-01'
+      },
+      {
+        'id'           => 7,
+        'title'        => 'A Wizard of Earthsea',
+        'author'       => 'Ursula K. LeGuin',
+        'series'       => 'Earthsea',
+        'category'     => 'Science Fiction and Fantasy',
+        'published_at' => '1968-11-01'
+      },
+      {
+        'id'           => 8,
+        'title'        => 'The Tombs of Atuan',
+        'author'       => 'Ursula K. LeGuin',
+        'series'       => 'Earthsea',
+        'category'     => 'Science Fiction and Fantasy',
+        'published_at' => '1970-12-01'
+      },
+      {
+        'id'           => 9,
+        'title'        => 'The Farthest Shore',
+        'author'       => 'Ursula K. LeGuin',
+        'series'       => 'Earthsea',
+        'category'     => 'Science Fiction and Fantasy',
+        'published_at' => '1972-09-01'
+      }
+    ].map(&:freeze).freeze
+  end
 end
diff --git a/spec/cuprum/collections/basic/collection_spec.rb b/spec/cuprum/collections/basic/collection_spec.rb
index 78b1054..9d4368f 100644
--- a/spec/cuprum/collections/basic/collection_spec.rb
+++ b/spec/cuprum/collections/basic/collection_spec.rb
@@ -20,7 +20,7 @@
   end
 
   shared_context 'when the collection has many items' do
-    let(:data)  { Cuprum::Collections::RSpec::BOOKS_FIXTURES }
+    let(:data)  { Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup }
     let(:items) { data }
   end
 
diff --git a/spec/cuprum/collections/basic/command_spec.rb b/spec/cuprum/collections/basic/command_spec.rb
index ed8dcfe..b890e0d 100644
--- a/spec/cuprum/collections/basic/command_spec.rb
+++ b/spec/cuprum/collections/basic/command_spec.rb
@@ -15,8 +15,10 @@
     )
   end
 
+  let(:data) do
+    Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup
+  end
   let(:collection_name)     { 'books' }
-  let(:data)                { Cuprum::Collections::RSpec::BOOKS_FIXTURES }
   let(:constructor_options) { {} }
 
   describe '.new' do
diff --git a/spec/cuprum/collections/basic/repository_spec.rb b/spec/cuprum/collections/basic/repository_spec.rb
index 120d567..6852b4b 100644
--- a/spec/cuprum/collections/basic/repository_spec.rb
+++ b/spec/cuprum/collections/basic/repository_spec.rb
@@ -94,7 +94,7 @@
 
     describe 'with data: an Array' do
       let(:data) do
-        Cuprum::Collections::RSpec::BOOKS_FIXTURES
+        Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup
       end
       let(:collection_options) { super().merge(data: data) }
 
@@ -103,7 +103,7 @@
 
     context 'when initialized with data: value' do
       let(:data) do
-        { 'books' => Cuprum::Collections::RSpec::BOOKS_FIXTURES }
+        { 'books' => Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup }
       end
       let(:constructor_options) { super().merge(data: data) }
 
@@ -141,7 +141,7 @@
 
     describe 'with data: an Array' do
       let(:data) do
-        Cuprum::Collections::RSpec::BOOKS_FIXTURES
+        Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup
       end
       let(:collection_options) { super().merge(data: data) }
 
@@ -150,7 +150,7 @@
 
     context 'when initialized with data: value' do
       let(:data) do
-        { 'books' => Cuprum::Collections::RSpec::BOOKS_FIXTURES }
+        { 'books' => Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup }
       end
       let(:constructor_options) { super().merge(data: data) }
 
diff --git a/spec/cuprum/collections/commands/find_one_matching_spec.rb b/spec/cuprum/collections/commands/find_one_matching_spec.rb
index ba109c1..ccf8bb7 100644
--- a/spec/cuprum/collections/commands/find_one_matching_spec.rb
+++ b/spec/cuprum/collections/commands/find_one_matching_spec.rb
@@ -71,7 +71,7 @@
     end
 
     context 'when there are many entities' do
-      let(:data) { Cuprum::Collections::RSpec::BOOKS_FIXTURES }
+      let(:data) { Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup }
 
       describe 'with attributes: a Hash that does not match any entities' do
         let(:attributes) { { 'author' => 'Jules Verne' } }
diff --git a/spec/integration/commands/create_spec.rb b/spec/integration/commands/create_spec.rb
index 192085d..75bae2d 100644
--- a/spec/integration/commands/create_spec.rb
+++ b/spec/integration/commands/create_spec.rb
@@ -11,8 +11,10 @@
 RSpec.describe Spec::Support::Commands::Create do
   subject(:command) { described_class.new(collection) }
 
+  let(:data) do
+    Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup
+  end
   let(:collection_name) { 'books' }
-  let(:data)            { Cuprum::Collections::RSpec::BOOKS_FIXTURES.dup }
   let(:collection_options) do
     {
       name: collection_name,
diff --git a/spec/integration/commands/destroy_spec.rb b/spec/integration/commands/destroy_spec.rb
index 7c3f7a7..5736ee3 100644
--- a/spec/integration/commands/destroy_spec.rb
+++ b/spec/integration/commands/destroy_spec.rb
@@ -8,8 +8,10 @@
 RSpec.describe Spec::Support::Commands::Destroy do
   subject(:command) { described_class.new(collection) }
 
+  let(:data) do
+    Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup
+  end
   let(:collection_name) { 'books' }
-  let(:data)            { Cuprum::Collections::RSpec::BOOKS_FIXTURES.dup }
   let(:collection_options) do
     {
       name: collection_name,
diff --git a/spec/integration/commands/index_spec.rb b/spec/integration/commands/index_spec.rb
index 9a1b9c5..76f00d8 100644
--- a/spec/integration/commands/index_spec.rb
+++ b/spec/integration/commands/index_spec.rb
@@ -8,8 +8,10 @@
 RSpec.describe Spec::Support::Commands::Index do
   subject(:command) { described_class.new(collection) }
 
+  let(:data) do
+    Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup
+  end
   let(:collection_name) { 'books' }
-  let(:data)            { Cuprum::Collections::RSpec::BOOKS_FIXTURES.dup }
   let(:collection_options) do
     {
       name: collection_name,
diff --git a/spec/integration/commands/show_spec.rb b/spec/integration/commands/show_spec.rb
index a07e996..9fd723b 100644
--- a/spec/integration/commands/show_spec.rb
+++ b/spec/integration/commands/show_spec.rb
@@ -8,8 +8,10 @@
 RSpec.describe Spec::Support::Commands::Show do
   subject(:command) { described_class.new(collection) }
 
+  let(:data) do
+    Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup
+  end
   let(:collection_name) { 'books' }
-  let(:data)            { Cuprum::Collections::RSpec::BOOKS_FIXTURES.dup }
   let(:collection_options) do
     {
       name: collection_name,
diff --git a/spec/integration/commands/update_spec.rb b/spec/integration/commands/update_spec.rb
index e6e48bc..7ea5610 100644
--- a/spec/integration/commands/update_spec.rb
+++ b/spec/integration/commands/update_spec.rb
@@ -11,8 +11,10 @@
 RSpec.describe Spec::Support::Commands::Update do
   subject(:command) { described_class.new(collection) }
 
+  let(:data) do
+    Cuprum::Collections::RSpec::Fixtures::BOOKS_FIXTURES.dup
+  end
   let(:collection_name) { 'books' }
-  let(:data)            { Cuprum::Collections::RSpec::BOOKS_FIXTURES.dup }
   let(:collection_options) do
     {
       name: collection_name,