Fix pattern match docs executbale test

docs/ast-pattern.md

@@ -30,7 +30,7 @@ specific:
 ```
 send
   { selector = info
-  , receiver = send{selector=logger}
+    receiver = send{selector=logger}
   }
 ```
 
@@ -84,7 +84,7 @@ But could be made required via:
 block
   { receiver = send
     { selector = log
-    , receiver = send{selector=logger}
+      receiver = send{selector=logger}
     }
   }
 ```

spec/unit/mutant/ast/pattern_spec.rb

@@ -168,5 +168,47 @@ def apply
         expect(apply).to eql(right(expected_node))
       end
     end
+
+    context 'example from docs' do
+      let(:string) { <<~'PATTERN' }
+        block
+          { receiver = send
+            { selector = log
+              receiver = send{selector=logger}
+            }
+          }
+      PATTERN
+
+      let(:expected_node) do
+        Mutant::AST::Pattern::Node.new(
+          type:       :block,
+          descendant: Mutant::AST::Pattern::Node::Descendant.new(
+            name:    :receiver,
+            pattern: Mutant::AST::Pattern::Node.new(
+              type:       :send,
+              attribute:  Mutant::AST::Pattern::Node::Attribute.new(
+                name:  :selector,
+                value: Mutant::AST::Pattern::Node::Attribute::Value::Single.new(value: :log)
+              ),
+              descendant: Mutant::AST::Pattern::Node::Descendant.new(
+                name:    :receiver,
+                pattern: Mutant::AST::Pattern::Node.new(
+                  type:      :send,
+                  attribute: Mutant::AST::Pattern::Node::Attribute.new(
+                    name:  :selector,
+                    value: Mutant::AST::Pattern::Node::Attribute::Value::Single.new(value: :logger)
+                  )
+                )
+              )
+            )
+          )
+        )
+      end
+
+      it 'returns expected node' do
+        expect(apply).to eql(right(expected_node))
+      end
+    end
+
   end
 end