Add more tests (#241)

* add form builder tests

* lint

* add client tests

* lint

* add non-existent file test

internal/test/helpers.go

@@ -0,0 +1,29 @@
+package test
+
+import (
+	"github.com/sashabaranov/go-openai/internal/test/checks"
+
+	"os"
+	"testing"
+)
+
+// CreateTestFile creates a fake file with "hello" as the content.
+func CreateTestFile(t *testing.T, path string) {
+	file, err := os.Create(path)
+	checks.NoError(t, err, "failed to create file")
+
+	if _, err = file.WriteString("hello"); err != nil {
+		t.Fatalf("failed to write to file %v", err)
+	}
+	file.Close()
+}
+
+// CreateTestDirectory creates a temporary folder which will be deleted when cleanup is called.
+func CreateTestDirectory(t *testing.T) (path string, cleanup func()) {
+	t.Helper()
+
+	path, err := os.MkdirTemp(os.TempDir(), "")
+	checks.NoError(t, err)
+
+	return path, func() { os.RemoveAll(path) }
+}