diff --git a/.gitignore b/.gitignore
index ecc90a3..660be00 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
 build/app
 vendor
 .idea
+coverage.out
+test-report.txt
diff --git a/Makefile b/Makefile
index 6f1be52..3a9ac2f 100644
--- a/Makefile
+++ b/Makefile
@@ -26,6 +26,13 @@ deps:
 	@go mod tidy
 	@go mod vendor
 
+test: clean build
+	@echo "==> Running tests"
+	@go test ./... -v -cpu 2 -race -timeout=30s -coverpkg=./... -coverprofile=$(ROOT_DIR)/coverage.out | tee $(ROOT_DIR)/test-report.txt
+	@cd / && go install github.com/axw/gocov/gocov@v1.0.0
+	@gocov convert $(ROOT_DIR)/coverage.out | gocov report
+	@go mod tidy
+
 .PHONY: clean
 clean:
 ifneq ($(wildcard $(ROOT_DIR)/vendor/.*),)
diff --git a/build/.gitkeep b/build/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/data/repository/author_repository.go b/data/repository/author_repository.go
index 8ad0465..a0e6ebf 100644
--- a/data/repository/author_repository.go
+++ b/data/repository/author_repository.go
@@ -9,7 +9,7 @@ func Authors() (authors []model.Author) {
 	authors = make([]model.Author, 10)
 	for i := 0; i < 10; i++ {
 		authors[i] = model.Author{
-			ID:        uint64(i),
+			ID:        uint64(i + 1),
 			FirstName: gofakeit.FirstName(),
 			LastName:  gofakeit.LastName(),
 			Books:     Books(),
diff --git a/data/repository/book_repository.go b/data/repository/book_repository.go
index fda30fb..8dd73b4 100644
--- a/data/repository/book_repository.go
+++ b/data/repository/book_repository.go
@@ -12,7 +12,7 @@ func Books() (books []model.Book) {
 	books = make([]model.Book, 10)
 	for i := 0; i < 10; i++ {
 		books[i] = model.Book{
-			ID:              uint64(i),
+			ID:              uint64(i + 1),
 			Name:            gofakeit.Phrase(),
 			PublicationDate: time.Now(),
 			Rate:            uint8(rand.Intn(5)),
diff --git a/go.mod b/go.mod
index fe1794e..6d33340 100644
--- a/go.mod
+++ b/go.mod
@@ -5,9 +5,11 @@ go 1.17
 require (
 	github.com/brianvoe/gofakeit/v6 v6.7.1
 	github.com/gin-gonic/gin v1.7.4
+	github.com/stretchr/testify v1.7.0
 )
 
 require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/gin-contrib/sse v0.1.0 // indirect
 	github.com/go-playground/locales v0.14.0 // indirect
 	github.com/go-playground/universal-translator v0.18.0 // indirect
@@ -18,10 +20,12 @@ require (
 	github.com/mattn/go-isatty v0.0.14 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/ugorji/go/codec v1.2.6 // indirect
 	golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97 // indirect
 	golang.org/x/sys v0.0.0-20210806184541-e5e7981a1069 // indirect
 	golang.org/x/text v0.3.6 // indirect
 	google.golang.org/protobuf v1.27.1 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
 )
diff --git a/handlers_test.go b/handlers_test.go
new file mode 100644
index 0000000..2b5955c
--- /dev/null
+++ b/handlers_test.go
@@ -0,0 +1,43 @@
+package main
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/Neur0toxine/demo-web-service-go/data/model"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAuthorsHandler(t *testing.T) {
+	req, err := http.NewRequest(http.MethodGet, "/authors", nil)
+	require.NoError(t, err)
+
+	r := router()
+	rec := httptest.NewRecorder()
+	r.ServeHTTP(rec, req)
+
+	data, err := io.ReadAll(rec.Body)
+	require.NoError(t, err)
+
+	var authors []model.Author
+	require.NoError(t, json.Unmarshal(data, &authors))
+
+	assert.Len(t, authors, 10)
+
+	for _, author := range authors {
+		assert.NotEmpty(t, author.ID)
+		assert.NotEmpty(t, author.FirstName)
+		assert.NotEmpty(t, author.LastName)
+		assert.Len(t, author.Books, 10)
+
+		for _, book := range author.Books {
+			assert.NotEmpty(t, book.ID)
+			assert.NotEmpty(t, book.Name)
+			assert.NotEmpty(t, book.PublicationDate)
+		}
+	}
+}