Improve some context descriptions in specs

spec/producer/core/cli_spec.rb

@@ -77,7 +77,7 @@ module Producer::Core
         cli.evaluate_recipe_file
       end
 
-      context 'error during recipe evaluation' do
+      context 'when recipe evaluation fails' do
         let(:recipe_file) { fixture_path_for('recipes/invalid.rb') }
         let(:stdout)      { StringIO.new }
         subject(:cli)     { CLI.new(arguments, stdout) }

spec/producer/core/recipe/dsl_spec.rb

@@ -36,7 +36,7 @@ module Producer::Core
         expect(dsl.evaluate(env)).to eq dsl
       end
 
-      context 'invalid recipe' do
+      context 'when recipe is invalid' do
         let(:filepath)  { fixture_path_for 'recipes/error.rb' }
         let(:recipe)    { Recipe.from_file(filepath) }
         subject(:dsl)   { Recipe::DSL.new File.read(filepath) }
@@ -67,8 +67,8 @@ module Producer::Core
           expect { dsl.evaluate(env) }.to raise_error(RuntimeError, 'error from recipe')
         end
 
-        context 'invalid sourced recipe' do
-          it 'reports the sourced recipe file path in the error' do
+        context 'when sourced recipe is invalid' do
+          it 'reports its file path in the error' do
             expect { dsl.evaluate(env) }.to raise_error(RuntimeError) { |e|
               expect(e.backtrace.first).to match /\A#{filepath}/
             }

spec/producer/core/task/dsl_spec.rb

@@ -13,7 +13,7 @@ module Producer::Core
     end
 
     describe '#condition' do
-      context 'condition is met (block evals to true)' do
+      context 'when met (block evals to true)' do
         let(:block) { Proc.new {
           condition { true }
           raise 'error after condition'
@@ -24,7 +24,7 @@ module Producer::Core
         end
       end
 
-      context 'condition is not met (block evals to false)' do
+      context 'when not met (block evals to false)' do
         let(:block) { Proc.new {
           condition { false }
           raise