diff --git a/parsers/nosql/misc_test.go b/parsers/nosql/misc_test.go
index bce01d5..a6bd26a 100644
--- a/parsers/nosql/misc_test.go
+++ b/parsers/nosql/misc_test.go
@@ -7,6 +7,7 @@ import (
 
 	"github.com/pikami/cosmium/parsers"
 	"github.com/pikami/cosmium/parsers/nosql"
+	testutils "github.com/pikami/cosmium/test_utils"
 )
 
 // For Parser Debugging
@@ -102,20 +103,8 @@ func Test_Parse(t *testing.T) {
 								Path: []string{"c", "id"},
 								Type: parsers.SelectItemTypeField,
 							},
-							parsers.SelectItem{
-								Type: parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{
-									Type:  parsers.ConstantTypeString,
-									Value: "123",
-								},
-							},
-							parsers.SelectItem{
-								Type: parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{
-									Type:  parsers.ConstantTypeString,
-									Value: "456",
-								},
-							},
+							testutils.SelectItem_Constant_String("123"),
+							testutils.SelectItem_Constant_String("456"),
 						},
 					},
 				},
diff --git a/parsers/nosql/string_functions_test.go b/parsers/nosql/string_functions_test.go
index 03ad113..e530a53 100644
--- a/parsers/nosql/string_functions_test.go
+++ b/parsers/nosql/string_functions_test.go
@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/pikami/cosmium/parsers"
+	testutils "github.com/pikami/cosmium/test_utils"
 )
 
 func Test_Execute_StringFunctions(t *testing.T) {
@@ -23,20 +24,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "123",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeBoolean,
-										Value: true,
-									},
-								},
+								testutils.SelectItem_Constant_String("123"),
+								testutils.SelectItem_Constant_Bool(true),
 							},
 						},
 					},
@@ -61,13 +50,7 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "123",
-									},
-								},
+								testutils.SelectItem_Constant_String("123"),
 								nil,
 							},
 						},
@@ -93,13 +76,7 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "123",
-									},
-								},
+								testutils.SelectItem_Constant_String("123"),
 								parsers.SelectItem{
 									Path: []string{"c", "pk"},
 									Type: parsers.SelectItemTypeField,
@@ -128,20 +105,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "123",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeBoolean,
-										Value: true,
-									},
-								},
+								testutils.SelectItem_Constant_String("123"),
+								testutils.SelectItem_Constant_Bool(true),
 							},
 						},
 					},
@@ -166,20 +131,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "123",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeBoolean,
-										Value: true,
-									},
-								},
+								testutils.SelectItem_Constant_String("123"),
+								testutils.SelectItem_Constant_Bool(true),
 							},
 						},
 					},
@@ -204,20 +157,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "123",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeBoolean,
-										Value: true,
-									},
-								},
+								testutils.SelectItem_Constant_String("123"),
+								testutils.SelectItem_Constant_Bool(true),
 							},
 						},
 					},
@@ -242,20 +183,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "2",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 1,
-									},
-								},
+								testutils.SelectItem_Constant_String("2"),
+								testutils.SelectItem_Constant_Int(1),
 							},
 						},
 					},
@@ -352,13 +281,7 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 5,
-									},
-								},
+								testutils.SelectItem_Constant_Int(5),
 							},
 						},
 					},
@@ -431,20 +354,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "old",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "new",
-									},
-								},
+								testutils.SelectItem_Constant_String("old"),
+								testutils.SelectItem_Constant_String("new"),
 							},
 						},
 					},
@@ -469,13 +380,7 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 3,
-									},
-								},
+								testutils.SelectItem_Constant_Int(3),
 							},
 						},
 					},
@@ -524,13 +429,7 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 3,
-									},
-								},
+								testutils.SelectItem_Constant_Int(3),
 							},
 						},
 					},
@@ -579,20 +478,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 1,
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 5,
-									},
-								},
+								testutils.SelectItem_Constant_Int(1),
+								testutils.SelectItem_Constant_Int(5),
 							},
 						},
 					},
diff --git a/parsers/nosql/were_test.go b/parsers/nosql/were_test.go
index fff28f8..dc3f6e7 100644
--- a/parsers/nosql/were_test.go
+++ b/parsers/nosql/were_test.go
@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/pikami/cosmium/parsers"
+	testutils "github.com/pikami/cosmium/test_utils"
 )
 
 func Test_Parse_Were(t *testing.T) {
@@ -22,10 +23,7 @@ func Test_Parse_Were(t *testing.T) {
 				Filters: parsers.ComparisonExpression{
 					Operation: "=",
 					Left:      parsers.SelectItem{Path: []string{"c", "isCool"}},
-					Right: parsers.SelectItem{
-						Type:  parsers.SelectItemTypeConstant,
-						Value: parsers.Constant{Type: parsers.ConstantTypeBoolean, Value: true},
-					},
+					Right:     testutils.SelectItem_Constant_Bool(true),
 				},
 			},
 		)
@@ -51,18 +49,12 @@ func Test_Parse_Were(t *testing.T) {
 						parsers.ComparisonExpression{
 							Operation: "=",
 							Left:      parsers.SelectItem{Path: []string{"c", "id"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeString, Value: "12345"},
-							},
+							Right:     testutils.SelectItem_Constant_String("12345"),
 						},
 						parsers.ComparisonExpression{
 							Operation: "=",
 							Left:      parsers.SelectItem{Path: []string{"c", "pk"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeInteger, Value: 123},
-							},
+							Right:     testutils.SelectItem_Constant_Int(123),
 						},
 					},
 				},
@@ -87,10 +79,7 @@ func Test_Parse_Were(t *testing.T) {
 						parsers.ComparisonExpression{
 							Operation: "=",
 							Left:      parsers.SelectItem{Path: []string{"c", "isCool"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeBoolean, Value: true},
-							},
+							Right:     testutils.SelectItem_Constant_Bool(true),
 						},
 						parsers.LogicalExpression{
 							Operation: parsers.LogicalExpressionTypeOr,
@@ -98,18 +87,12 @@ func Test_Parse_Were(t *testing.T) {
 								parsers.ComparisonExpression{
 									Operation: "=",
 									Left:      parsers.SelectItem{Path: []string{"c", "id"}},
-									Right: parsers.SelectItem{
-										Type:  parsers.SelectItemTypeConstant,
-										Value: parsers.Constant{Type: parsers.ConstantTypeString, Value: "123"},
-									},
+									Right:     testutils.SelectItem_Constant_String("123"),
 								},
 								parsers.ComparisonExpression{
 									Operation: "=",
 									Left:      parsers.SelectItem{Path: []string{"c", "id"}},
-									Right: parsers.SelectItem{
-										Type:  parsers.SelectItemTypeConstant,
-										Value: parsers.Constant{Type: parsers.ConstantTypeString, Value: "456"},
-									},
+									Right:     testutils.SelectItem_Constant_String("456"),
 								},
 							},
 						},
@@ -135,43 +118,28 @@ func Test_Parse_Were(t *testing.T) {
 				Filters: parsers.LogicalExpression{
 					Expressions: []interface{}{
 						parsers.ComparisonExpression{
-							Left: parsers.SelectItem{Path: []string{"c", "boolean"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeBoolean, Value: true},
-							},
+							Left:      parsers.SelectItem{Path: []string{"c", "boolean"}},
+							Right:     testutils.SelectItem_Constant_Bool(true),
 							Operation: "=",
 						},
 						parsers.ComparisonExpression{
-							Left: parsers.SelectItem{Path: []string{"c", "integer"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeInteger, Value: 1},
-							},
+							Left:      parsers.SelectItem{Path: []string{"c", "integer"}},
+							Right:     testutils.SelectItem_Constant_Int(1),
 							Operation: "=",
 						},
 						parsers.ComparisonExpression{
-							Left: parsers.SelectItem{Path: []string{"c", "float"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeFloat, Value: 6.9},
-							},
+							Left:      parsers.SelectItem{Path: []string{"c", "float"}},
+							Right:     testutils.SelectItem_Constant_Float(6.9),
 							Operation: "=",
 						},
 						parsers.ComparisonExpression{
-							Left: parsers.SelectItem{Path: []string{"c", "string"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeString, Value: "hello"},
-							},
+							Left:      parsers.SelectItem{Path: []string{"c", "string"}},
+							Right:     testutils.SelectItem_Constant_String("hello"),
 							Operation: "=",
 						},
 						parsers.ComparisonExpression{
-							Left: parsers.SelectItem{Path: []string{"c", "param"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeParameterConstant, Value: "@param_id1"},
-							},
+							Left:      parsers.SelectItem{Path: []string{"c", "param"}},
+							Right:     testutils.SelectItem_Constant_Parameter("@param_id1"),
 							Operation: "=",
 						},
 					},
diff --git a/query_executors/memory_executor/misc_test.go b/query_executors/memory_executor/misc_test.go
index aae3693..72995ae 100644
--- a/query_executors/memory_executor/misc_test.go
+++ b/query_executors/memory_executor/misc_test.go
@@ -6,6 +6,7 @@ import (
 
 	"github.com/pikami/cosmium/parsers"
 	memoryexecutor "github.com/pikami/cosmium/query_executors/memory_executor"
+	testutils "github.com/pikami/cosmium/test_utils"
 )
 
 func testQueryExecute(
@@ -111,20 +112,8 @@ func Test_Execute(t *testing.T) {
 								Path: []string{"c", "id"},
 								Type: parsers.SelectItemTypeField,
 							},
-							parsers.SelectItem{
-								Type: parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{
-									Type:  parsers.ConstantTypeString,
-									Value: "123",
-								},
-							},
-							parsers.SelectItem{
-								Type: parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{
-									Type:  parsers.ConstantTypeString,
-									Value: "456",
-								},
-							},
+							testutils.SelectItem_Constant_String("123"),
+							testutils.SelectItem_Constant_String("456"),
 						},
 					},
 				},
diff --git a/query_executors/memory_executor/string_functions_test.go b/query_executors/memory_executor/string_functions_test.go
index 836b384..85a751d 100644
--- a/query_executors/memory_executor/string_functions_test.go
+++ b/query_executors/memory_executor/string_functions_test.go
@@ -5,6 +5,7 @@ import (
 
 	"github.com/pikami/cosmium/parsers"
 	memoryexecutor "github.com/pikami/cosmium/query_executors/memory_executor"
+	testutils "github.com/pikami/cosmium/test_utils"
 )
 
 func Test_Execute_StringFunctions(t *testing.T) {
@@ -33,20 +34,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "pk"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "aaa",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeBoolean,
-										Value: true,
-									},
-								},
+								testutils.SelectItem_Constant_String("aaa"),
+								testutils.SelectItem_Constant_Bool(true),
 							},
 						},
 					},
@@ -81,13 +70,7 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "pk"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "aaa",
-									},
-								},
+								testutils.SelectItem_Constant_String("aaa"),
 								nil,
 							},
 						},
@@ -119,20 +102,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: " ",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: 123,
-									},
-								},
+								testutils.SelectItem_Constant_String(" "),
+								testutils.SelectItem_Constant_Int(123),
 								parsers.SelectItem{
 									Path: []string{"c", "pk"},
 									Type: parsers.SelectItemTypeField,
@@ -171,20 +142,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "2",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeBoolean,
-										Value: true,
-									},
-								},
+								testutils.SelectItem_Constant_String("2"),
+								testutils.SelectItem_Constant_Bool(true),
 							},
 						},
 					},
@@ -219,20 +178,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "3",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeBoolean,
-										Value: true,
-									},
-								},
+								testutils.SelectItem_Constant_String("3"),
+								testutils.SelectItem_Constant_Bool(true),
 							},
 						},
 					},
@@ -267,20 +214,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "id"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "1",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeBoolean,
-										Value: true,
-									},
-								},
+								testutils.SelectItem_Constant_String("1"),
+								testutils.SelectItem_Constant_Bool(true),
 							},
 						},
 					},
@@ -315,20 +250,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "str"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "o",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 4,
-									},
-								},
+								testutils.SelectItem_Constant_String("o"),
+								testutils.SelectItem_Constant_Int(4),
 							},
 						},
 					},
@@ -397,13 +320,7 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "str"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 3,
-									},
-								},
+								testutils.SelectItem_Constant_Int(3),
 							},
 						},
 					},
@@ -506,20 +423,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "str"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "world",
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeString,
-										Value: "universe",
-									},
-								},
+								testutils.SelectItem_Constant_String("world"),
+								testutils.SelectItem_Constant_String("universe"),
 							},
 						},
 					},
@@ -554,13 +459,7 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "str"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 3,
-									},
-								},
+								testutils.SelectItem_Constant_Int(3),
 							},
 						},
 					},
@@ -629,13 +528,7 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "str"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 3,
-									},
-								},
+								testutils.SelectItem_Constant_Int(3),
 							},
 						},
 					},
@@ -704,20 +597,8 @@ func Test_Execute_StringFunctions(t *testing.T) {
 									Path: []string{"c", "str"},
 									Type: parsers.SelectItemTypeField,
 								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 2,
-									},
-								},
-								parsers.SelectItem{
-									Type: parsers.SelectItemTypeConstant,
-									Value: parsers.Constant{
-										Type:  parsers.ConstantTypeInteger,
-										Value: 4,
-									},
-								},
+								testutils.SelectItem_Constant_Int(2),
+								testutils.SelectItem_Constant_Int(4),
 							},
 						},
 					},
diff --git a/query_executors/memory_executor/were_test.go b/query_executors/memory_executor/were_test.go
index c8749d1..f3b0289 100644
--- a/query_executors/memory_executor/were_test.go
+++ b/query_executors/memory_executor/were_test.go
@@ -5,6 +5,7 @@ import (
 
 	"github.com/pikami/cosmium/parsers"
 	memoryexecutor "github.com/pikami/cosmium/query_executors/memory_executor"
+	testutils "github.com/pikami/cosmium/test_utils"
 )
 
 func Test_Execute_Where(t *testing.T) {
@@ -26,10 +27,7 @@ func Test_Execute_Where(t *testing.T) {
 				Filters: parsers.ComparisonExpression{
 					Operation: "=",
 					Left:      parsers.SelectItem{Path: []string{"c", "isCool"}},
-					Right: parsers.SelectItem{
-						Type:  parsers.SelectItemTypeConstant,
-						Value: parsers.Constant{Type: parsers.ConstantTypeBoolean, Value: true},
-					},
+					Right:     testutils.SelectItem_Constant_Bool(true),
 				},
 			},
 			mockData,
@@ -52,10 +50,7 @@ func Test_Execute_Where(t *testing.T) {
 				Filters: parsers.ComparisonExpression{
 					Operation: "=",
 					Left:      parsers.SelectItem{Path: []string{"c", "id"}},
-					Right: parsers.SelectItem{
-						Type:  parsers.SelectItemTypeConstant,
-						Value: parsers.Constant{Type: parsers.ConstantTypeParameterConstant, Value: "@param_id"},
-					},
+					Right:     testutils.SelectItem_Constant_Parameter("@param_id"),
 				},
 				Parameters: map[string]interface{}{
 					"@param_id": "456",
@@ -83,18 +78,12 @@ func Test_Execute_Where(t *testing.T) {
 						parsers.ComparisonExpression{
 							Operation: "=",
 							Left:      parsers.SelectItem{Path: []string{"c", "id"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeString, Value: "67890"},
-							},
+							Right:     testutils.SelectItem_Constant_String("67890"),
 						},
 						parsers.ComparisonExpression{
 							Operation: "=",
 							Left:      parsers.SelectItem{Path: []string{"c", "pk"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeInteger, Value: 456},
-							},
+							Right:     testutils.SelectItem_Constant_Int(456),
 						},
 					},
 				},
@@ -120,10 +109,7 @@ func Test_Execute_Where(t *testing.T) {
 						parsers.ComparisonExpression{
 							Operation: "=",
 							Left:      parsers.SelectItem{Path: []string{"c", "isCool"}},
-							Right: parsers.SelectItem{
-								Type:  parsers.SelectItemTypeConstant,
-								Value: parsers.Constant{Type: parsers.ConstantTypeBoolean, Value: true},
-							},
+							Right:     testutils.SelectItem_Constant_Bool(true),
 						},
 						parsers.LogicalExpression{
 							Operation: parsers.LogicalExpressionTypeOr,
@@ -131,18 +117,12 @@ func Test_Execute_Where(t *testing.T) {
 								parsers.ComparisonExpression{
 									Operation: "=",
 									Left:      parsers.SelectItem{Path: []string{"c", "id"}},
-									Right: parsers.SelectItem{
-										Type:  parsers.SelectItemTypeConstant,
-										Value: parsers.Constant{Type: parsers.ConstantTypeString, Value: "123"},
-									},
+									Right:     testutils.SelectItem_Constant_String("123"),
 								},
 								parsers.ComparisonExpression{
 									Operation: "=",
 									Left:      parsers.SelectItem{Path: []string{"c", "id"}},
-									Right: parsers.SelectItem{
-										Type:  parsers.SelectItemTypeConstant,
-										Value: parsers.Constant{Type: parsers.ConstantTypeString, Value: "456"},
-									},
+									Right:     testutils.SelectItem_Constant_String("456"),
 								},
 							},
 						},