test: add comprehensive test suite with testability refactoring

Extract error-returning internal functions (performRequest, toFile,
buildItems, sendItems, deleteItem) from their log.Fatal wrappers to
enable unit testing. Add 28 tests covering models, HTTP client, file
I/O, and send/receive workflows using httptest and t.TempDir.

Author: nicolaiarocci

CHANGELOG.md

@@ -3,6 +3,8 @@
 ## In Development
 
 - fix: Il comando `get --json` scriveva anche il file su disco invece di restituire solo il JSON.
+- new: Test suite completa (28 test) con refactoring per testabilità delle funzioni critiche.
+- new: Sezione Contributing nel README con istruzioni per build, test e cross-compile.
 
 ## [1.0.0-beta.1] - 2025-07-08
 

README.md

@@ -40,6 +40,43 @@ See the [Installation guide][3].
 
 Quickstart and context available at the [Invoicetronic website][1].
 
+## Contributing
+
+### Prerequisites
+
+- Go 1.23+
+- An [Invoicetronic API][1] key (for manual/integration testing)
+
+### Build
+
+```bash
+go build
+```
+
+### Test
+
+```bash
+go test ./...
+```
+
+Run with the race detector:
+
+```bash
+go test -race ./...
+```
+
+Tests use the standard library only (`testing` + `net/http/httptest`), with no external dependencies. API calls are mocked via `httptest.NewServer`; filesystem tests use `t.TempDir()`.
+
+### Cross-compile
+
+Requires `PACKAGE_VERSION` to be set:
+
+```bash
+PACKAGE_VERSION=1.0.0 make all
+```
+
+Target a single platform with `make windows`, `make linux`, or `make macos`.
+
 [1]: https://invoicetronic.com/docs/quickstart/invoice-quickstart/
 [2]: https://invoicetronic.com/docs/sdk/
 [3]: https://invoicetronic.com/docs/cli/#installation-guide

cmd/helpers_test.go

@@ -0,0 +1,36 @@
+package cmd
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/spf13/viper"
+)
+
+func setupViper(t *testing.T) {
+	t.Helper()
+	viper.Reset()
+	viper.Set("host", "https://api.invoicetronic.com")
+	viper.Set("apikey", "test-api-key")
+	viper.Set("verbose", false)
+}
+
+func newTestServer(t *testing.T, handler http.HandlerFunc) *httptest.Server {
+	t.Helper()
+	server := httptest.NewServer(handler)
+	t.Cleanup(server.Close)
+	viper.Set("host", server.URL)
+	return server
+}
+
+func createTempFile(t *testing.T, dir, name, content string) string {
+	t.Helper()
+	p := filepath.Join(dir, name)
+	if err := os.WriteFile(p, []byte(content), 0644); err != nil {
+		t.Fatal(err)
+	}
+	return p
+}

cmd/receive.go

@@ -78,14 +78,20 @@ func receiveRun(_ *cobra.Command, _ []string) {
 	}
 
 }
-func Delete(id int) {
+func deleteItem(id int, client *http.Client) error {
 	url := BuildEndpointUrl("receive", strconv.Itoa(id))
 	req, err := http.NewRequest("DELETE", url.String(), nil)
 	if err != nil {
-		log.Fatal(err)
+		return err
 	}
+	_, _, err = performRequest(req, client)
+	return err
+}
 
-	PerformRequest(req, &http.Client{})
+func Delete(id int) {
+	if err := deleteItem(id, &http.Client{}); err != nil {
+		log.Fatal(err)
+	}
 }
 
 func getFullFilePath(dest, filename string) (string, error) {

cmd/receive_test.go

@@ -0,0 +1,57 @@
+package cmd
+
+import (
+	"net/http"
+	"testing"
+)
+
+func TestDeleteItem(t *testing.T) {
+	t.Run("success", func(t *testing.T) {
+		setupViper(t)
+
+		var method, path string
+		newTestServer(t, func(w http.ResponseWriter, r *http.Request) {
+			method = r.Method
+			path = r.URL.Path
+			w.WriteHeader(200)
+			_, _ = w.Write([]byte(`{}`))
+		})
+
+		err := deleteItem(42, &http.Client{})
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if method != "DELETE" {
+			t.Errorf("method = %q, want DELETE", method)
+		}
+		if path != "/v1/receive/42" {
+			t.Errorf("path = %q, want /v1/receive/42", path)
+		}
+	})
+
+	t.Run("not found", func(t *testing.T) {
+		setupViper(t)
+		newTestServer(t, func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(404)
+			_, _ = w.Write([]byte("not found"))
+		})
+
+		err := deleteItem(999, &http.Client{})
+		if err == nil {
+			t.Fatal("expected error for 404, got nil")
+		}
+	})
+
+	t.Run("server error", func(t *testing.T) {
+		setupViper(t)
+		newTestServer(t, func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(500)
+			_, _ = w.Write([]byte("internal error"))
+		})
+
+		err := deleteItem(1, &http.Client{})
+		if err == nil {
+			t.Fatal("expected error for 500, got nil")
+		}
+	})
+}

cmd/root.go

@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"encoding/base64"
+	"fmt"
 	"io"
 	"log"
 	"net/http"
@@ -56,32 +57,43 @@ func BasicAuth() string {
 	return base64.StdEncoding.EncodeToString([]byte(auth))
 }
 
-func PerformRequest(req *http.Request, client *http.Client) (*http.Response, []byte) {
+func performRequest(req *http.Request, client *http.Client) (*http.Response, []byte, error) {
 	req.Header.Set("Authorization", "Basic "+BasicAuth())
 	req.Header.Set("Content-Type", "application/json")
 
 	resp, err := client.Do(req)
 	if err != nil {
-		log.Fatal(err)
+		return nil, nil, err
 	}
 	defer func(Body io.ReadCloser) {
 		_ = Body.Close()
 	}(resp.Body)
 
 	respBody, err := io.ReadAll(resp.Body)
 	if err != nil {
-		log.Fatal(err)
+		return nil, nil, err
 	}
 
 	if !(resp.StatusCode >= 200 && resp.StatusCode < 300) {
-		log.Printf("Send failed (%v)", resp.Status)
-		if len(respBody) > 0 {
-			log.Println(string(respBody))
-		}
-		os.Exit(1)
+		return resp, respBody, fmt.Errorf("request failed (%v): %s", resp.Status, string(respBody))
 	}
 
-	return resp, respBody
+	return resp, respBody, nil
+}
+
+func PerformRequest(req *http.Request, client *http.Client) (*http.Response, []byte) {
+	resp, body, err := performRequest(req, client)
+	if err != nil {
+		if resp != nil {
+			log.Printf("Send failed (%v)", resp.Status)
+			if len(body) > 0 {
+				log.Println(string(body))
+			}
+			os.Exit(1)
+		}
+		log.Fatal(err)
+	}
+	return resp, body
 }
 
 func init() {
@@ -101,33 +113,32 @@ func init() {
 
 }
 
-func ToFile(filename string, payload string, encoding string) {
+func toFile(filename, payload, encoding, destDir string) error {
 	Verbose("Processing payload for %v with encoding %v\n", filename, encoding)
 	var decodedData []byte
-	
+
 	if encoding == "Base64" {
 		Verbose("Decoding base64 payload for %v\n", filename)
 		var err error
 		decodedData, err = base64.StdEncoding.DecodeString(payload)
 		if err != nil {
-			log.Fatalf("Error decoding base64 payload for %v: %v", filename, err)
+			return fmt.Errorf("error decoding base64 payload for %v: %v", filename, err)
 		}
 	} else {
 		Verbose("Using payload as plain string for %v\n", filename)
 		decodedData = []byte(payload)
 	}
 
 	var filePath string
-	var err error
-	if outputDir != "" {
-		filePath, err = getFullFilePath(outputDir, filename)
+	if destDir != "" {
+		var err error
+		filePath, err = getFullFilePath(destDir, filename)
 		if err != nil {
-			log.Fatal(err)
+			return err
 		}
-
-		err = createDirectoryIfNotExists(outputDir)
+		err = createDirectoryIfNotExists(destDir)
 		if err != nil {
-			log.Fatal(err)
+			return err
 		}
 	} else {
 		filePath = filename
@@ -136,7 +147,7 @@ func ToFile(filename string, payload string, encoding string) {
 	Verbose("Creating file %v\n", filename)
 	file, err := os.Create(filePath)
 	if err != nil {
-		log.Fatalf("Error creating "+filename+": %v", err)
+		return fmt.Errorf("error creating %s: %v", filename, err)
 	}
 	defer func(file *os.File) {
 		_ = file.Close()
@@ -145,10 +156,17 @@ func ToFile(filename string, payload string, encoding string) {
 	Verbose("Writing to file %v\n", filename)
 	_, err = file.Write(decodedData)
 	if err != nil {
-		log.Fatalf("Error writing to file "+filename+": %v", err)
+		return fmt.Errorf("error writing to file %s: %v", filename, err)
 	}
 
 	Verbose("Write to %v succeeded\n", filename)
+	return nil
+}
+
+func ToFile(filename, payload, encoding string) {
+	if err := toFile(filename, payload, encoding, outputDir); err != nil {
+		log.Fatal(err)
+	}
 }
 
 func createDirectoryIfNotExists(dest string) error {