diff --git a/node/expr/binary_op/t_binary_op_test.go b/node/expr/binary_op/t_binary_op_test.go
new file mode 100644
index 0000000..46d8a1d
--- /dev/null
+++ b/node/expr/binary_op/t_binary_op_test.go
@@ -0,0 +1,643 @@
+package binary_op_test
+
+import (
+	"bytes"
+	"reflect"
+	"testing"
+	
+	"github.com/kylelemons/godebug/pretty"
+	
+	"github.com/z7zmey/php-parser/node"
+	"github.com/z7zmey/php-parser/node/expr"
+	"github.com/z7zmey/php-parser/node/expr/binary_op"
+	"github.com/z7zmey/php-parser/node/stmt"
+	"github.com/z7zmey/php-parser/php5"
+	"github.com/z7zmey/php-parser/php7"
+)
+
+func assertEqual(t *testing.T, expected interface{}, actual interface{}) {
+	if !reflect.DeepEqual(expected, actual) {
+		diff := pretty.Compare(expected, actual)
+
+		if diff != "" {
+			t.Errorf("diff: (-expected +actual)\n%s", diff)
+		} else {
+			t.Errorf("expected and actual are not equal\n")
+		}
+	}
+}
+
+func TestBitwiseAnd(t *testing.T) {
+	src := `<? $a & $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.BitwiseAnd{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestBitwiseOr(t *testing.T) {
+	src := `<? $a | $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.BitwiseOr{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestBitwiseXor(t *testing.T) {
+	src := `<? $a ^ $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.BitwiseXor{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestBooleanAnd(t *testing.T) {
+	src := `<? $a && $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.BooleanAnd{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestBooleanOr(t *testing.T) {
+	src := `<? $a || $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.BooleanOr{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestCoalesce(t *testing.T) {
+	src := `<? $a ?? $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Coalesce{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestConcat(t *testing.T) {
+	src := `<? $a . $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Concat{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestDiv(t *testing.T) {
+	src := `<? $a / $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Div{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestEqual(t *testing.T) {
+	src := `<? $a == $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Equal{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestGreaterOrEqual(t *testing.T) {
+	src := `<? $a >= $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.GreaterOrEqual{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestGreater(t *testing.T) {
+	src := `<? $a > $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Greater{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestIdentical(t *testing.T) {
+	src := `<? $a === $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Identical{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestLogicalAnd(t *testing.T) {
+	src := `<? $a and $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.LogicalAnd{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestLogicalOr(t *testing.T) {
+	src := `<? $a or $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.LogicalOr{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestLogicalXor(t *testing.T) {
+	src := `<? $a xor $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.LogicalXor{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestMinus(t *testing.T) {
+	src := `<? $a - $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Minus{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestMod(t *testing.T) {
+	src := `<? $a % $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Mod{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestMul(t *testing.T) {
+	src := `<? $a * $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Mul{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestNotEqual(t *testing.T) {
+	src := `<? $a != $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.NotEqual{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestNotIdentical(t *testing.T) {
+	src := `<? $a !== $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.NotIdentical{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestPlus(t *testing.T) {
+	src := `<? $a + $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Plus{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestPow(t *testing.T) {
+	src := `<? $a ** $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Pow{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestShiftLeft(t *testing.T) {
+	src := `<? $a << $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.ShiftLeft{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestShiftRight(t *testing.T) {
+	src := `<? $a >> $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.ShiftRight{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestSmallerOrEqual(t *testing.T) {
+	src := `<? $a <= $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.SmallerOrEqual{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestSmaller(t *testing.T) {
+	src := `<? $a < $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Smaller{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+
+	actual, _, _ = php5.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
+
+func TestSpaceship(t *testing.T) {
+	src := `<? $a <=> $b;`
+
+	expected := &stmt.StmtList{
+		Stmts: []node.Node{
+			&stmt.Expression{
+				Expr: &binary_op.Spaceship{
+					BinaryOp: binary_op.BinaryOp{
+						Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+						Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+					},
+				},
+			},
+		},
+	}
+
+	actual, _, _ := php7.Parse(bytes.NewBufferString(src), "test.php")
+	assertEqual(t, expected, actual)
+}
diff --git a/node/expr/binary_op/t_visitor_test.go b/node/expr/binary_op/t_visitor_test.go
new file mode 100644
index 0000000..dfa084e
--- /dev/null
+++ b/node/expr/binary_op/t_visitor_test.go
@@ -0,0 +1,346 @@
+package binary_op_test
+
+import (
+	"reflect"
+	"testing"
+	
+	"github.com/kylelemons/godebug/pretty"
+	
+	"github.com/z7zmey/php-parser/node"
+	"github.com/z7zmey/php-parser/node/expr"
+	"github.com/z7zmey/php-parser/node/expr/binary_op"
+	"github.com/z7zmey/php-parser/walker"
+)
+
+var nodesToTest = []struct {
+	node                node.Node // node
+	expectedVisitedKeys []string  // visited keys
+	expectedAttributes  map[string]interface{}
+}{
+	{
+		&binary_op.BitwiseAnd{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.BitwiseOr{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.BitwiseXor{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.BooleanAnd{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.BooleanOr{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Coalesce{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Concat{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Div{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Equal{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.GreaterOrEqual{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Greater{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Identical{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.LogicalAnd{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.LogicalOr{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.LogicalXor{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Minus{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Mod{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Mul{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.NotEqual{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.NotIdentical{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Plus{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Pow{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.ShiftLeft{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.ShiftRight{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.SmallerOrEqual{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Smaller{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+	{
+		&binary_op.Spaceship{
+			BinaryOp: binary_op.BinaryOp{
+				Left: &expr.Variable{VarName: &node.Identifier{Value: "$a"}},
+				Right: &expr.Variable{VarName: &node.Identifier{Value: "$b"}},
+			},
+		},
+		[]string{"Left", "Right"},
+		map[string]interface{}{},
+	},
+}
+
+type visitorMock struct {
+	visitChildren bool
+	visitedKeys   []string
+}
+
+func (v *visitorMock) EnterNode(n walker.Walker) bool { return v.visitChildren }
+func (v *visitorMock) GetChildrenVisitor(key string) walker.Visitor {
+	v.visitedKeys = append(v.visitedKeys, key)
+	return &visitorMock{v.visitChildren, nil}
+}
+func (v *visitorMock) LeaveNode(n walker.Walker) {}
+
+func TestVisitorDisableChildren(t *testing.T) {
+	for _, tt := range nodesToTest {
+		v := &visitorMock{false, nil}
+		tt.node.Walk(v)
+
+		expected := []string{}
+		actual := v.visitedKeys
+
+		diff := pretty.Compare(expected, actual)
+		if diff != "" {
+			t.Errorf("%s diff: (-expected +actual)\n%s", reflect.TypeOf(tt.node), diff)
+		}
+	}
+}
+
+func TestVisitor(t *testing.T) {
+	for _, tt := range nodesToTest {
+		v := &visitorMock{true, nil}
+		tt.node.Walk(v)
+
+		expected := tt.expectedVisitedKeys
+		actual := v.visitedKeys
+
+		diff := pretty.Compare(expected, actual)
+		if diff != "" {
+			t.Errorf("%s diff: (-expected +actual)\n%s", reflect.TypeOf(tt.node), diff)
+		}
+	}
+}
+
+// test Attributes()
+
+func TestNameAttributes(t *testing.T) {
+	for _, tt := range nodesToTest {
+		expected := tt.expectedAttributes
+		actual := tt.node.Attributes()
+
+		diff := pretty.Compare(expected, actual)
+		if diff != "" {
+			t.Errorf("%s diff: (-expected +actual)\n%s", reflect.TypeOf(tt.node), diff)
+		}
+	}
+}