todo/internal/auth/handler/login_test.go

package handler

import (
	"bytes"
	"context"
	"encoding/json"
	"log/slog"

	"errors"
	"net/http"
	"net/http/httptest"
	"testing"

	"gitea.michaelthomson.dev/mthomson/habits/internal/auth/service"
)

type MockLoginer struct {
	LoginFunc func(ctx context.Context, email string, password string) (string, error)
}

func (m *MockLoginer) Login(ctx context.Context, email string, password string) (string, error) {
	return m.LoginFunc(ctx, email, password)
}

func TestLogin(t *testing.T) {
	logger := slog.Default()
	t.Run("returns 200 for existing user with correct credentials", func(t *testing.T) {
		loginRequest := LoginRequest{Email: "test@test.com", Password: "password"}

		token := "examplejwt"

		service := MockLoginer{
			LoginFunc: func(ctx context.Context, email string, password string) (string, error) {
				return token, nil
			},
		}

		handler := HandleLogin(logger, &service)

		requestBody, err := json.Marshal(loginRequest)

		if err != nil {
			t.Fatalf("Failed to marshal request %+v: %v", loginRequest, err)
		}

		req := httptest.NewRequest(http.MethodPost, "/login", bytes.NewBuffer(requestBody))
		res := httptest.NewRecorder()

		handler(res, req)

		AssertStatusCodes(t, res.Code, http.StatusOK)
		AssertToken(t, res, token)
	})

	t.Run("returns 401 for existing user with incorrect credentials", func(t *testing.T) {
		loginRequest := LoginRequest{Email: "test@test.com", Password: "password"}

		service := MockLoginer{
			LoginFunc: func(ctx context.Context, email string, password string) (string, error) {
				return "", service.ErrUnauthorized
			},
		}

		handler := HandleLogin(logger, &service)

		requestBody, err := json.Marshal(loginRequest)

		if err != nil {
			t.Fatalf("Failed to marshal request %+v: %v", loginRequest, err)
		}

		req := httptest.NewRequest(http.MethodPost, "/login", bytes.NewBuffer(requestBody))
		res := httptest.NewRecorder()

		handler(res, req)

		AssertStatusCodes(t, res.Code, http.StatusUnauthorized)
	})

	t.Run("returns 401 for non-existing user", func(t *testing.T) {
		loginRequest := LoginRequest{Email: "test@test.com", Password: "password"}

		service := MockLoginer{
			LoginFunc: func(ctx context.Context, email string, password string) (string, error) {
				return "", service.ErrNotFound
			},
		}

		handler := HandleLogin(logger, &service)

		requestBody, err := json.Marshal(loginRequest)

		if err != nil {
			t.Fatalf("Failed to marshal request %+v: %v", loginRequest, err)
		}

		req := httptest.NewRequest(http.MethodPost, "/login", bytes.NewBuffer(requestBody))
		res := httptest.NewRecorder()

		handler(res, req)

		AssertStatusCodes(t, res.Code, http.StatusUnauthorized)
	})

	t.Run("returns 400 with bad json", func(t *testing.T) {
		handler := HandleLogin(logger, nil)

		badStruct := struct {
			Foo string
		}{
			Foo: "bar",
		}

		requestBody, err := json.Marshal(badStruct)

		if err != nil {
			t.Fatalf("Failed to marshal request %+v: %v", badStruct, err)
		}

		req := httptest.NewRequest(http.MethodPost, "/login", bytes.NewBuffer(requestBody))
		res := httptest.NewRecorder()

		handler(res, req)

		AssertStatusCodes(t, res.Code, http.StatusBadRequest)
	})

	t.Run("returns 500 arbitrary errors", func(t *testing.T) {
		loginRequest := LoginRequest{Email: "test@test.com", Password: "password"}

		service := MockLoginer{
			LoginFunc: func(ctx context.Context, email string, password string) (string, error) {
				return "", errors.New("foo bar")
			},
		}

		handler := HandleLogin(logger, &service)

		requestBody, err := json.Marshal(loginRequest)

		if err != nil {
			t.Fatalf("Failed to marshal request %+v: %v", loginRequest, err)
		}

		req := httptest.NewRequest(http.MethodPost, "/login", bytes.NewBuffer(requestBody))
		res := httptest.NewRecorder()

		handler(res, req)

		AssertStatusCodes(t, res.Code, http.StatusInternalServerError)
	})

}

func AssertStatusCodes(t testing.TB, got, want int) {
	t.Helper()
	if got != want {
		t.Errorf("got status code: %v, want status code: %v", want, got)
	}
}

func AssertToken(t testing.TB, res *httptest.ResponseRecorder, want string) {
	t.Helper()
	got := res.Result().Cookies()[0].Value
	if got != want {
		t.Errorf("got cookie: %q, want cookie: %q", got, want)
	}
}