Add files api tests (#238)

* drop support for downloading files

* use form builder to submit files

* update doc

* add form builder tests

files_test.go

@@ -1,14 +1,15 @@
-package openai_test
+package openai //nolint:testpackage // testing private field
 
 import (
-	. "github.com/sashabaranov/go-openai"
 	"github.com/sashabaranov/go-openai/internal/test"
 	"github.com/sashabaranov/go-openai/internal/test/checks"
 
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
+	"os"
 	"strconv"
 	"testing"
 	"time"
@@ -34,7 +35,7 @@ func TestFileUpload(t *testing.T) {
 		Purpose:  "fine-tune",
 	}
 	_, err = client.CreateFile(ctx, req)
-	checks.NoError(t, err, "CreateFile erro")
+	checks.NoError(t, err, "CreateFile error")
 }
 
 // handleCreateFile Handles the images endpoint by the test server.
@@ -78,3 +79,50 @@ func handleCreateFile(w http.ResponseWriter, r *http.Request) {
 	resBytes, _ = json.Marshal(fileReq)
 	fmt.Fprint(w, string(resBytes))
 }
+
+func TestFileUploadWithFailingFormBuilder(t *testing.T) {
+	config := DefaultConfig("")
+	config.BaseURL = ""
+	client := NewClientWithConfig(config)
+	mockBuilder := &mockFormBuilder{}
+	client.createFormBuilder = func(io.Writer) formBuilder {
+		return mockBuilder
+	}
+
+	ctx := context.Background()
+	req := FileRequest{
+		FileName: "test.go",
+		FilePath: "client.go",
+		Purpose:  "fine-tune",
+	}
+
+	mockError := fmt.Errorf("mockWriteField error")
+	mockBuilder.mockWriteField = func(string, string) error {
+		return mockError
+	}
+	_, err := client.CreateFile(ctx, req)
+	checks.ErrorIs(t, err, mockError, "CreateFile should return error if form builder fails")
+
+	mockError = fmt.Errorf("mockCreateFormFile error")
+	mockBuilder.mockWriteField = func(string, string) error {
+		return nil
+	}
+	mockBuilder.mockCreateFormFile = func(string, *os.File) error {
+		return mockError
+	}
+	_, err = client.CreateFile(ctx, req)
+	checks.ErrorIs(t, err, mockError, "CreateFile should return error if form builder fails")
+
+	mockError = fmt.Errorf("mockClose error")
+	mockBuilder.mockWriteField = func(string, string) error {
+		return nil
+	}
+	mockBuilder.mockCreateFormFile = func(string, *os.File) error {
+		return nil
+	}
+	mockBuilder.mockClose = func() error {
+		return mockError
+	}
+	_, err = client.CreateFile(ctx, req)
+	checks.ErrorIs(t, err, mockError, "CreateFile should return error if form builder fails")
+}