diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 94966ab..4d890d6 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -15,3 +15,4 @@ require 'rubella/weighting/per_count'
 require 'rubella/weighting/per_value'
 require 'rubella/weighting/exponential'
 require 'rubella/weighting/per_overall_load'
+require 'rubella/output/base'
diff --git a/spec/unit/rubella/output/base/field_size_eql_spec.rb b/spec/unit/rubella/output/base/field_size_eql_spec.rb
new file mode 100644
index 0000000..104aa7e
--- /dev/null
+++ b/spec/unit/rubella/output/base/field_size_eql_spec.rb
@@ -0,0 +1,13 @@
+require 'spec_helper'
+
+describe Rubella::Output::Base, '.field_size' do
+
+  it "returns the given field_sitze" do
+    output = Rubella::Output::Base.new nil, 0
+    expect(output.field_size).to eq(0)
+
+    output.field_size = 5
+    expect(output.field_size).to eq(5)
+  end
+
+end
diff --git a/spec/unit/rubella/output/base/field_size_spec.rb b/spec/unit/rubella/output/base/field_size_spec.rb
new file mode 100644
index 0000000..c3725ca
--- /dev/null
+++ b/spec/unit/rubella/output/base/field_size_spec.rb
@@ -0,0 +1,11 @@
+require 'spec_helper'
+
+describe Rubella::Output::Base, '.field_size' do
+
+  it "returns the given field_sitze" do
+    output = Rubella::Output::Base.new nil, 5
+
+    expect(output.field_size).to eq(5)
+  end
+
+end
diff --git a/spec/unit/rubella/output/base/new_spec.rb b/spec/unit/rubella/output/base/new_spec.rb
new file mode 100644
index 0000000..4038ed3
--- /dev/null
+++ b/spec/unit/rubella/output/base/new_spec.rb
@@ -0,0 +1,28 @@
+require 'spec_helper'
+
+describe Rubella::Output::Base, '.new' do
+
+  it "creates a new Rubella::Output" do
+    output = Rubella::Output::Base.new nil, nil
+
+    expect(output).to be_kind_of(Rubella::Output::Base)
+  end
+
+  it "uses the given data" do
+    output = Rubella::Output::Implementation.new Rubella::Storage.new([]), nil
+
+    expect(output.data).to be_kind_of(Rubella::Storage)
+    expect(output.data.data).to eq([])
+  end
+
+  it "uses the given field_size" do
+    output = Rubella::Output::Base.new nil, 5
+
+    expect(output.field_size).to eq(5)
+  end
+
+end
+
+class Rubella::Output::Implementation < Rubella::Output::Base
+  attr_reader :data
+end
diff --git a/spec/unit/rubella/output/base/render_spec.rb b/spec/unit/rubella/output/base/render_spec.rb
new file mode 100644
index 0000000..ddb5330
--- /dev/null
+++ b/spec/unit/rubella/output/base/render_spec.rb
@@ -0,0 +1,11 @@
+require 'spec_helper'
+
+describe Rubella::Output::Base, '.render' do
+  
+  it "raises NotImplementedError" do
+    output = Rubella::Output::Base.new nil, nil
+
+    expect{ output.render }.to raise_error(NotImplementedError)
+  end
+
+end