From 49d29a8b856654e16ab75640389a1a8f2597a9b2 Mon Sep 17 00:00:00 2001
From: sneak <sneak@sneak.berlin>
Date: Mon, 28 Sep 2026 15:49:18 +0000
Subject: [PATCH] Test that an empty fit on /v1/image/ is refused with 400
 (closes #139)

A fit in the URL with an empty value is served as cover today and
verifies against a signature made for cover. This test asks for a 400
naming fit instead; it fails until the route refuses it.

Model: opus-5-5
---
 internal/handlers/handlers_internal_test.go | 38 +++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/internal/handlers/handlers_internal_test.go b/internal/handlers/handlers_internal_test.go
index 780a46c..35c1522 100644
--- a/internal/handlers/handlers_internal_test.go
+++ b/internal/handlers/handlers_internal_test.go
@@ -356,3 +356,41 @@ func TestHandleImage_InvalidQuery_Returns400(t *testing.T) {
 		})
 	}
 }
+
+// TestHandleImage_EmptyFit_Returns400 verifies that the plain image route
+// answers a fit that is in the URL but empty with 400 naming fit, instead of
+// serving the image as cover. Only a fit missing from the URL means cover.
+func TestHandleImage_EmptyFit_Returns400(t *testing.T) {
+	t.Parallel()
+
+	fix := setupTestHandler(t)
+
+	r := chi.NewRouter()
+	r.Get("/v1/image/*", fix.handler.HandleImage())
+
+	req := httptest.NewRequestWithContext(t.Context(), http.MethodGet,
+		"/v1/image/"+fix.goodHost+"/images/photo.jpg/50x50.jpeg?fit=", nil)
+	rec := httptest.NewRecorder()
+
+	r.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusBadRequest)
+	}
+
+	t.Logf("GET %s: %d %s", req.URL, rec.Code, rec.Body)
+
+	var body struct {
+		Error string `json:"error"`
+	}
+
+	err := json.NewDecoder(rec.Body).Decode(&body)
+	if err != nil {
+		t.Fatalf("decoding response body: %v", err)
+	}
+
+	wantError := `invalid fit: not a fit mode, got ""`
+	if body.Error != wantError {
+		t.Errorf("error = %q, want %q", body.Error, wantError)
+	}
+}