test: add TraceID, ErrorHandler, Recover middleware tests

- TestTraceID_GeneratesAndAttachesTraceID
- TestTraceID_ExtractsExistingTraceID
- TestErrorHandler_HandlesErrors
- TestRecover_HandlesPanic

Fix test to use errors.New instead of gin.Error{Err: nil}

internal/api/middleware/runtime_test.go

@@ -1,6 +1,7 @@
 package middleware
 
 import (
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -137,3 +138,81 @@ func TestNoStoreSensitiveResponses_DoesNotAttachHeadersToNonAuthRoutes(t *testin
 		t.Fatalf("did not expect cache-control header, got %q", got)
 	}
 }
+
+// ---------- TraceID middleware ----------
+
+func TestTraceID_GeneratesAndAttachesTraceID(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	c.Request = httptest.NewRequest(http.MethodGet, "/api/v1/users", nil)
+
+	TraceID()(c)
+
+	traceID := c.GetString("trace_id")
+	if traceID == "" {
+		t.Fatal("expected trace_id to be set")
+	}
+	if len(traceID) < 8 {
+		t.Fatalf("trace_id should be reasonably long, got %q", traceID)
+	}
+
+	if got := recorder.Header().Get("X-Trace-ID"); got != traceID {
+		t.Fatalf("expected X-Trace-ID header to match trace_id, got %q", got)
+	}
+}
+
+func TestTraceID_ExtractsExistingTraceID(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	existingTraceID := "existing-trace-id-12345"
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	c.Request = httptest.NewRequest(http.MethodGet, "/api/v1/users", nil)
+	c.Request.Header.Set("X-Trace-ID", existingTraceID)
+
+	TraceID()(c)
+
+	traceID := c.GetString("trace_id")
+	if traceID != existingTraceID {
+		t.Fatalf("expected trace_id to be extracted from header, got %q", traceID)
+	}
+}
+
+// ---------- Error handling middleware ----------
+
+func TestErrorHandler_HandlesErrors(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	c.Request = httptest.NewRequest(http.MethodGet, "/api/v1/users", nil)
+
+	c.Error(errors.New("test error"))
+
+	ErrorHandler()(c)
+
+	if recorder.Code != http.StatusInternalServerError {
+		t.Fatalf("expected status 500, got %d", recorder.Code)
+	}
+}
+
+func TestRecover_HandlesPanic(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	recorder := httptest.NewRecorder()
+	c, router := gin.CreateTestContext(recorder)
+	c.Request = httptest.NewRequest(http.MethodGet, "/panic", nil)
+
+	router.Use(Recover())
+	router.GET("/panic", func(c *gin.Context) {
+		panic("test panic")
+	})
+
+	router.ServeHTTP(recorder, c.Request)
+
+	if recorder.Code != http.StatusInternalServerError {
+		t.Fatalf("expected status 500 after panic, got %d", recorder.Code)
+	}
+}