Add fail-fast on init for missing provider credentials

internal/server/streaming_writer_test.go

@@ -0,0 +1,53 @@
+package server
+
+import (
+	"io"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type nonFlusherRecorder struct {
+	recorder         *httptest.ResponseRecorder
+	writeHeaderCalls int
+}
+
+func newNonFlusherRecorder() *nonFlusherRecorder {
+	return &nonFlusherRecorder{recorder: httptest.NewRecorder()}
+}
+
+func (w *nonFlusherRecorder) Header() http.Header {
+	return w.recorder.Header()
+}
+
+func (w *nonFlusherRecorder) Write(b []byte) (int, error) {
+	return w.recorder.Write(b)
+}
+
+func (w *nonFlusherRecorder) WriteHeader(statusCode int) {
+	w.writeHeaderCalls++
+	w.recorder.WriteHeader(statusCode)
+}
+
+func (w *nonFlusherRecorder) StatusCode() int {
+	return w.recorder.Code
+}
+
+func (w *nonFlusherRecorder) BodyString() string {
+	return w.recorder.Body.String()
+}
+
+func TestHandleStreamingResponseWithoutFlusherWritesSingleErrorHeader(t *testing.T) {
+	s := New(nil, nil, slog.New(slog.NewTextHandler(io.Discard, nil)))
+	req := httptest.NewRequest(http.MethodPost, "/v1/responses", nil)
+	w := newNonFlusherRecorder()
+
+	s.handleStreamingResponse(w, req, nil, nil, nil, nil, nil)
+
+	assert.Equal(t, 1, w.writeHeaderCalls)
+	assert.Equal(t, http.StatusInternalServerError, w.StatusCode())
+	assert.Contains(t, w.BodyString(), "streaming not supported")
+}