diff --git a/CHANGELOG.md b/CHANGELOG.md
index 50839e4..5af89d7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,17 @@
 # Changelog
 
+## 1.4.0
+
+The "Signs And Portents" Update
+
+### Results
+
+Added `Result.success` and `Result.failure`, which provide singleton results with respective `:success` and `:failure` statuses.
+
+### RSpec
+
+Updated `ParameterValidationExamples` to support lazy evaluation of the `message:` parameter, as well as any additional parameters passed along with `type:`. Parameters passed as a `Proc` will be evaluated in the context of the current example group.
+
 ## 1.3.1
 
 Added support for Ruby 4.0.
diff --git a/lib/cuprum/rspec/deferred/parameter_validation_examples.rb b/lib/cuprum/rspec/deferred/parameter_validation_examples.rb
index aeacea3..79e25ef 100644
--- a/lib/cuprum/rspec/deferred/parameter_validation_examples.rb
+++ b/lib/cuprum/rspec/deferred/parameter_validation_examples.rb
@@ -57,10 +57,19 @@ module ParameterValidationExamples
 
     deferred_examples 'should validate the parameter' \
     do |name, type = nil, message: nil, **options|
+      let(:expected_message) do
+        message.is_a?(Proc) ? instance_exec(&message) : message
+      end
+      let(:expected_options) do
+        options.transform_values do |value|
+          value.is_a?(Proc) ? instance_exec(&value) : value
+        end
+      end
+
       it 'should return a failing result with InvalidParameters error' do
         expected_failure =
-          message ||
-          tools.assertions.error_message_for(type, as: name, **options)
+          expected_message ||
+          tools.assertions.error_message_for(type, as: name, **expected_options)
         expected_error   = Cuprum::Errors::InvalidParameters.new(
           command_class: subject.class,
           failures:      [expected_failure]
@@ -71,11 +80,5 @@ module ParameterValidationExamples
           .with_error(expected_error)
       end
     end
-
-    private
-
-    def tools
-      SleepingKingStudios::Tools::Toolbelt.instance
-    end
   end
 end
diff --git a/spec/cuprum/rspec/deferred/parameter_validation_examples_spec.fixtures.rb b/spec/cuprum/rspec/deferred/parameter_validation_examples_spec.fixtures.rb
index d8803be..280b60b 100644
--- a/spec/cuprum/rspec/deferred/parameter_validation_examples_spec.fixtures.rb
+++ b/spec/cuprum/rspec/deferred/parameter_validation_examples_spec.fixtures.rb
@@ -27,11 +27,45 @@
     klass.validate :quantity, Integer
   end
 
-  def call_command
+  define_method :call_command do
     command.call(name, quantity)
   end
 
+  define_method :tools do
+    SleepingKingStudios::Tools::Toolbelt.instance
+  end
+
   describe '"should validate the parameter" examples' do
+    describe 'with message: a Proc' do
+      context 'when the parameters are valid' do
+        include_deferred 'should validate the parameter',
+          :quantity,
+          message: -> { 'quantity is invalid' }
+      end
+
+      context 'when the parameters are invalid with non-matching errors' do
+        let(:quantity) { nil }
+
+        include_deferred 'should validate the parameter',
+          :quantity,
+          message: -> { 'quantity is invalid' }
+      end
+
+      context 'when the parameters are invalid with matching error' do
+        let(:quantity) { nil }
+
+        include_deferred 'should validate the parameter',
+          :quantity,
+          message: lambda {
+            tools.assertions.error_message_for(
+              :instance_of,
+              as:       'quantity',
+              expected: Integer
+            )
+          }
+      end
+    end
+
     describe 'with message: value' do
       context 'when the parameters are valid' do
         include_deferred 'should validate the parameter',
@@ -73,6 +107,13 @@ def call_command
           :name,
           'sleeping_king_studios.tools.assertions.presence',
           as: 'item name'
+
+        describe 'with as: a Proc' do
+          include_deferred 'should validate the parameter',
+            :name,
+            'sleeping_king_studios.tools.assertions.presence',
+            as: -> { 'item name' }
+        end
       end
 
       context 'when the parameters are invalid with matching error' do
@@ -82,6 +123,13 @@ def call_command
           :name,
           'sleeping_king_studios.tools.assertions.presence',
           as: 'item name'
+
+        describe 'with as: a Proc' do
+          include_deferred 'should validate the parameter',
+            :name,
+            'sleeping_king_studios.tools.assertions.presence',
+            as: -> { 'item name' }
+        end
       end
     end
   end
diff --git a/spec/cuprum/rspec/deferred/parameter_validation_examples_spec.rb b/spec/cuprum/rspec/deferred/parameter_validation_examples_spec.rb
index 87a4cad..4413caf 100644
--- a/spec/cuprum/rspec/deferred/parameter_validation_examples_spec.rb
+++ b/spec/cuprum/rspec/deferred/parameter_validation_examples_spec.rb
@@ -15,22 +15,27 @@
   end
   let(:expected_failing) do
     <<~EXAMPLES.lines.map(&:strip)
+      Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with message: a Proc when the parameters are valid should return a failing result with InvalidParameters error
+      Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with message: a Proc when the parameters are invalid with non-matching errors should return a failing result with InvalidParameters error
       Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with message: value when the parameters are valid should return a failing result with InvalidParameters error
       Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with message: value when the parameters are invalid with non-matching errors should return a failing result with InvalidParameters error
       Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with type: value when the parameters are valid should return a failing result with InvalidParameters error
       Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with type: value when the parameters are invalid with non-matching errors should return a failing result with InvalidParameters error
+      Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with type: value when the parameters are invalid with non-matching errors with as: a Proc should return a failing result with InvalidParameters error
     EXAMPLES
   end
   let(:expected_passing) do
     <<~EXAMPLES.lines.map(&:strip)
+      Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with message: a Proc when the parameters are invalid with matching error should return a failing result with InvalidParameters error
       Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with message: value when the parameters are invalid with matching error should return a failing result with InvalidParameters error
       Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with type: value when the parameters are invalid with matching error should return a failing result with InvalidParameters error
+      Cuprum::RSpec::Deferred::ParameterValidationExamples "should validate the parameter" examples with type: value when the parameters are invalid with matching error with as: a Proc should return a failing result with InvalidParameters error
     EXAMPLES
   end
 
-  it { expect(result.summary).to be == '6 examples, 4 failures' }
+  it { expect(result.summary).to be == '11 examples, 7 failures' }
 
-  it { expect(result.failing_examples).to be == expected_failing }
+  it { expect(result.failing_examples).to deep_match(expected_failing) }
 
-  it { expect(result.passing_examples).to be == expected_passing }
+  it { expect(result.passing_examples).to deep_match(expected_passing) }
 end