diff --git a/lib/parser/crystal.rb b/lib/parser/crystal.rb
index 4d4decf..f63010f 100644
--- a/lib/parser/crystal.rb
+++ b/lib/parser/crystal.rb
@@ -31,8 +31,8 @@ module Parser
     include Operators
     include ModuleDef
 
-    rule(:root_body)    {(module_definition | class_definition | function_definition | expression  | call_site | 
-                          basic_type | hash_constant | array_constant )}
+    rule(:root_body)    {(module_definition | class_definition | function_definition | expression  | 
+                          operator_expression | call_site | basic_type | hash_constant | array_constant )}
     rule(:root)         { root_body.repeat.as(:expression_list) }
   end
 end
diff --git a/test/roots/test_operators.rb b/test/roots/test_operators.rb
new file mode 100644
index 0000000..492495d
--- /dev/null
+++ b/test/roots/test_operators.rb
@@ -0,0 +1,76 @@
+require_relative "../parser_helper"
+
+class TestExpressions < MiniTest::Test
+  # include the magic (setup and parse -> test method translation), see there
+  include ParserHelper
+
+  def simple_op op
+    @string_input    = "5 #{op} 3"
+    @parse_output = {:expression_list=>[{:l=>{:integer=>"5"}, :o=>"#{op} ", :r=>{:integer=>"3"}}]}
+    @transform_output = Ast::ExpressionList.new( [Ast::OperatorExpression.new(op, Ast::IntegerExpression.new(5),Ast::IntegerExpression.new(3))])
+  end
+  def test_simple_multiply
+    simple_op "*"
+  end
+  def test_simple_devide
+    simple_op "/"
+  end
+  def test_simple_plus
+    simple_op "+"
+  end
+  def test_simple_minus
+    simple_op "-"
+  end
+  def test_simple_greater
+    simple_op ">"
+  end
+  def test_simple_smaller
+    simple_op "<"
+  end
+  def test_op_variable
+    @string_input    = "a + 35"
+    @parse_output = {:expression_list=>[{:l=>{:name=>"a"}, :o=>"+ ", :r=>{:integer=>"35"}}]}
+    @transform_output = Ast::ExpressionList.new( [Ast::OperatorExpression.new("+", Ast::NameExpression.new(:a),Ast::IntegerExpression.new(35))])
+  end
+  def test_op_two_variable
+    @string_input    = "a - b"
+    @parse_output = {:expression_list=>[{:l=>{:name=>"a"}, :o=>"- ", :r=>{:name=>"b"}}]}
+    @transform_output = Ast::ExpressionList.new( [Ast::OperatorExpression.new("-", Ast::NameExpression.new(:a),Ast::NameExpression.new(:b))])
+  end
+  def test_op_instance_variable
+    @string_input    = "@a - 5"
+    @parse_output = {:expression_list=>[{:l=>{:instance_variable=>{:name=>"a"}}, :o=>"- ", :r=>{:integer=>"5"}}]}
+    @transform_output = Ast::ExpressionList.new( [Ast::OperatorExpression.new("-", Ast::VariableExpression.new(:a),Ast::IntegerExpression.new(5))])
+  end
+  def test_op_variable_string
+    @string_input    = 'a - "st"'
+    @parse_output = {:expression_list=>[{:l=>{:name=>"a"}, :o=>"- ", :r=>{:string=>[{:char=>"s"}, {:char=>"t"}]}}]}
+    @transform_output = Ast::ExpressionList.new( [Ast::OperatorExpression.new("-", Ast::NameExpression.new(:a),Ast::StringExpression.new("st"))])
+  end
+  def test_two_same_ops
+    @string_input    = '2 + 3 + 4'
+    @parse_output = {:expression_list=>[{:l=>{:l=>{:integer=>"2"}, :o=>"+ ", :r=>{:integer=>"3"}}, :o=>"+ ", :r=>{:integer=>"4"}}]}
+    @transform_output = Ast::ExpressionList.new( [Ast::OperatorExpression.new("+", Ast::OperatorExpression.new("+", Ast::IntegerExpression.new(2),Ast::IntegerExpression.new(3)),Ast::IntegerExpression.new(4))])
+  end
+  def test_two_different_ops
+    @string_input    = '2 + 3 * 4'
+    @parse_output = {:expression_list=>[{:l=>{:integer=>"2"}, :o=>"+ ", :r=>{:l=>{:integer=>"3"}, :o=>"* ", :r=>{:integer=>"4"}}}]}
+    @transform_output = Ast::ExpressionList.new( [Ast::OperatorExpression.new("+", Ast::IntegerExpression.new(2),Ast::OperatorExpression.new("*", Ast::IntegerExpression.new(3),Ast::IntegerExpression.new(4)))])
+  end
+  def test_two_different_ops_order
+    @string_input    = '2 * 3 + 4'
+    @parse_output = {:expression_list=>[{:l=>{:l=>{:integer=>"2"}, :o=>"* ", :r=>{:integer=>"3"}}, :o=>"+ ", :r=>{:integer=>"4"}}]}
+    @transform_output = Ast::ExpressionList.new( [Ast::OperatorExpression.new("+", Ast::OperatorExpression.new("*", Ast::IntegerExpression.new(2),Ast::IntegerExpression.new(3)),Ast::IntegerExpression.new(4))])
+  end
+  def test_assignment
+    @string_input    = "a = 5"
+    @parse_output = {:expression_list=>[{:l=>{:name=>"a"}, :o=>"= ", :r=>{:integer=>"5"}}]}
+    @transform_output = Ast::ExpressionList.new( [Ast::AssignmentExpression.new(Ast::NameExpression.new(:a),Ast::IntegerExpression.new(5))])
+  end
+  def test_assignment_instance
+    @string_input    = "@a = 5"
+    @parse_output = {:expression_list=>[{:l=>{:instance_variable=>{:name=>"a"}}, :o=>"= ", :r=>{:integer=>"5"}}]}
+    @transform_output = Ast::ExpressionList.new( [Ast::AssignmentExpression.new(Ast::VariableExpression.new(:a),Ast::IntegerExpression.new(5))])
+  end
+
+end
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