diff --git a/controller/book_test.go b/controller/book_test.go
index c4821aa0..bb272104 100644
--- a/controller/book_test.go
+++ b/controller/book_test.go
@@ -11,6 +11,7 @@ import (
 	"github.com/ybkuroki/go-webapp-sample/model"
 	"github.com/ybkuroki/go-webapp-sample/model/dto"
 	"github.com/ybkuroki/go-webapp-sample/test"
+	"github.com/ybkuroki/go-webapp-sample/util"
 )
 
 type BookDtoForBindError struct {
@@ -28,7 +29,7 @@ func TestGetBook_Success(t *testing.T) {
 
 	setUpTestData(container)
 
-	uri := test.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
+	uri := util.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
 	req := httptest.NewRequest("GET", uri, nil)
 	rec := httptest.NewRecorder()
 
@@ -49,7 +50,7 @@ func TestGetBook_Failure(t *testing.T) {
 
 	setUpTestData(container)
 
-	uri := test.NewRequestBuilder().URL(APIBooks).PathParams("9999").Build().GetRequestURL()
+	uri := util.NewRequestBuilder().URL(APIBooks).PathParams("9999").Build().GetRequestURL()
 	req := httptest.NewRequest("GET", uri, nil)
 	rec := httptest.NewRecorder()
 
@@ -67,7 +68,7 @@ func TestGetBookList_Success(t *testing.T) {
 
 	setUpTestData(container)
 
-	uri := test.NewRequestBuilder().URL(APIBooks).RequestParams("query", "Test").RequestParams("page", "0").RequestParams("size", "5").Build().GetRequestURL()
+	uri := util.NewRequestBuilder().URL(APIBooks).RequestParams("query", "Test").RequestParams("page", "0").RequestParams("size", "5").Build().GetRequestURL()
 	req := httptest.NewRequest("GET", uri, nil)
 	rec := httptest.NewRecorder()
 
@@ -142,7 +143,7 @@ func TestUpdateBook_Success(t *testing.T) {
 	setUpTestData(container)
 
 	param := createBookForUpdate()
-	uri := test.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
+	uri := util.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
 	req := test.NewJSONRequest("PUT", uri, param)
 	rec := httptest.NewRecorder()
 
@@ -164,7 +165,7 @@ func TestUpdateBook_BindError(t *testing.T) {
 	setUpTestData(container)
 
 	param := createBookForBindError()
-	uri := test.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
+	uri := util.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
 	req := test.NewJSONRequest("PUT", uri, param)
 	rec := httptest.NewRecorder()
 
@@ -184,7 +185,7 @@ func TestUpdateBook_ValidationError(t *testing.T) {
 	setUpTestData(container)
 
 	param := createBookForValidationError()
-	uri := test.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
+	uri := util.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
 	req := test.NewJSONRequest("PUT", uri, param)
 	rec := httptest.NewRecorder()
 
@@ -206,7 +207,7 @@ func TestDeleteBook_Success(t *testing.T) {
 	entity := &model.Book{}
 	data, _ := entity.FindByID(container.GetRepository(), 1)
 
-	uri := test.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
+	uri := util.NewRequestBuilder().URL(APIBooks).PathParams("1").Build().GetRequestURL()
 	req := test.NewJSONRequest("DELETE", uri, nil)
 	rec := httptest.NewRecorder()
 
@@ -224,7 +225,7 @@ func TestDeleteBook_Failure(t *testing.T) {
 
 	setUpTestData(container)
 
-	uri := test.NewRequestBuilder().URL(APIBooks).PathParams("9999").Build().GetRequestURL()
+	uri := util.NewRequestBuilder().URL(APIBooks).PathParams("9999").Build().GetRequestURL()
 	req := test.NewJSONRequest("DELETE", uri, nil)
 	rec := httptest.NewRecorder()
 
diff --git a/service/account_test.go b/service/account_test.go
index 7ebbc1ce..febd2082 100644
--- a/service/account_test.go
+++ b/service/account_test.go
@@ -18,7 +18,7 @@ func TestAuthenticateByUsernameAndPassword_Success(t *testing.T) {
 	data, _ := a.FindByName(container.GetRepository(), "test")
 
 	assert.Equal(t, data, account)
-	assert.Equal(t, true, result)
+	assert.True(t, result)
 }
 
 func TestAuthenticateByUsernameAndPassword_EntityNotFound(t *testing.T) {
@@ -28,7 +28,7 @@ func TestAuthenticateByUsernameAndPassword_EntityNotFound(t *testing.T) {
 	result, account := service.AuthenticateByUsernameAndPassword("abcde", "abcde")
 
 	assert.Equal(t, (*model.Account)(nil), account)
-	assert.Equal(t, false, result)
+	assert.False(t, result)
 }
 
 func TestAuthenticateByUsernameAndPassword_AuthenticationFailure(t *testing.T) {
@@ -38,5 +38,5 @@ func TestAuthenticateByUsernameAndPassword_AuthenticationFailure(t *testing.T) {
 	result, account := service.AuthenticateByUsernameAndPassword("test", "abcde")
 
 	assert.Equal(t, (*model.Account)(nil), account)
-	assert.Equal(t, false, result)
+	assert.False(t, result)
 }
diff --git a/service/book_test.go b/service/book_test.go
index 3824088b..febf6830 100644
--- a/service/book_test.go
+++ b/service/book_test.go
@@ -20,7 +20,7 @@ func TestFindByID_Success(t *testing.T) {
 	result, err := service.FindByID("1")
 
 	assert.Equal(t, uint(1), result.ID)
-	assert.Equal(t, nil, err)
+	assert.NoError(t, err)
 	assert.NotEmpty(t, result)
 }
 
@@ -45,7 +45,7 @@ func TestFindByID_EntityNotFound(t *testing.T) {
 	result, err := service.FindByID("9999")
 
 	assert.Equal(t, (*model.Book)(nil), result)
-	assert.Equal(t, errors.New("failed to fetch data"), err)
+	assert.Error(t, err, "failed to fetch data")
 }
 
 func TestFindAllBooks_Success(t *testing.T) {
@@ -56,8 +56,8 @@ func TestFindAllBooks_Success(t *testing.T) {
 	service := NewBookService(container)
 	result, err := service.FindAllBooks()
 
-	assert.Equal(t, 2, len(*result))
-	assert.Equal(t, nil, err)
+	assert.Len(t, *result, 2)
+	assert.NoError(t, err)
 }
 
 func TestFindAllBooksByPage_Success(t *testing.T) {
@@ -72,8 +72,8 @@ func TestFindAllBooksByPage_Success(t *testing.T) {
 	assert.Equal(t, 1, result.TotalPages)
 	assert.Equal(t, 0, result.Page)
 	assert.Equal(t, 5, result.Size)
-	assert.Equal(t, 2, len(*result.Content))
-	assert.Equal(t, nil, err)
+	assert.Len(t, *result.Content, 2)
+	assert.NoError(t, err)
 }
 
 func TestFindBooksByTitle_Success(t *testing.T) {
@@ -88,8 +88,8 @@ func TestFindBooksByTitle_Success(t *testing.T) {
 	assert.Equal(t, 1, result.TotalPages)
 	assert.Equal(t, 0, result.Page)
 	assert.Equal(t, 5, result.Size)
-	assert.Equal(t, 1, len(*result.Content))
-	assert.Equal(t, nil, err)
+	assert.Len(t, *result.Content, 1)
+	assert.NoError(t, err)
 }
 
 func TestCreateBook_Success(t *testing.T) {
diff --git a/service/category_test.go b/service/category_test.go
index 588314b8..dbb66453 100644
--- a/service/category_test.go
+++ b/service/category_test.go
@@ -13,5 +13,5 @@ func TestFindAllCategories_Success(t *testing.T) {
 	service := NewCategoryService(container)
 	result := service.FindAllCategories()
 
-	assert.Equal(t, 3, len(*result))
+	assert.Len(t, *result, 3)
 }
diff --git a/service/format_test.go b/service/format_test.go
index f4d4510f..37110d70 100644
--- a/service/format_test.go
+++ b/service/format_test.go
@@ -13,5 +13,5 @@ func TestFindAllFormats_Success(t *testing.T) {
 	service := NewFormatService(container)
 	result := service.FindAllFormats()
 
-	assert.Equal(t, 2, len(*result))
+	assert.Len(t, *result, 2)
 }
diff --git a/test/request_builder.go b/util/request_builder.go
similarity index 99%
rename from test/request_builder.go
rename to util/request_builder.go
index a59f7875..3e4a9618 100644
--- a/test/request_builder.go
+++ b/util/request_builder.go
@@ -1,4 +1,4 @@
-package test
+package util
 
 import "strings"
 
diff --git a/util/request_builder_test.go b/util/request_builder_test.go
new file mode 100644
index 00000000..153112c7
--- /dev/null
+++ b/util/request_builder_test.go
@@ -0,0 +1,17 @@
+package util
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetRequestURL_PathParam(t *testing.T) {
+	result := NewRequestBuilder().URL("https://www.test/").PathParams("1").PathParams("test").Build().GetRequestURL()
+	assert.Equal(t, "https://www.test/1/test", result)
+}
+
+func TestGetRequestURL_RequestParam(t *testing.T) {
+	result := NewRequestBuilder().URL("https://www.test/").RequestParams("hoge", "123").RequestParams("huga", "abcd").Build().GetRequestURL()
+	assert.Equal(t, "https://www.test/?hoge=123&huga=abcd", result)
+}
diff --git a/util/strings_test.go b/util/strings_test.go
new file mode 100644
index 00000000..824092d0
--- /dev/null
+++ b/util/strings_test.go
@@ -0,0 +1,34 @@
+package util
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsNumeric_True(t *testing.T) {
+	result := IsNumeric("123")
+	assert.True(t, result)
+}
+
+func TestIsNumeric_False(t *testing.T) {
+	result := IsNumeric("abcde")
+	assert.False(t, result)
+}
+
+func TestConvertToInt_Number(t *testing.T) {
+	result := ConvertToInt("123")
+	assert.Equal(t, int(123), result)
+	assert.IsType(t, int(123), result)
+}
+
+func TestConvertToInt_NotNumber(t *testing.T) {
+	result := ConvertToInt("abcde/:12@s#$%'()")
+	assert.Equal(t, 0, result)
+}
+
+func TestConvertToUint_Number(t *testing.T) {
+	result := ConvertToUint("123")
+	assert.Equal(t, uint(123), result)
+	assert.IsType(t, uint(123), result)
+}