Fix library_id filter test for dev database compatibility

Update TestCollectionSearchLibraryFilter to check for specific test
books rather than exact counts, making tests resilient to changing
dev database data.

Changes:
- Modified "no filter" test case to check both test books are present
- Enhanced shouldContain to support comma-separated book ID lists
- Added strings import for ID list processing
- Skip exact count check when expectedCount is 0

Rationale:
The library_id filter was working correctly. The test failure was due
to running against a dev database with pre-existing data. When no
library_id filter is provided, the API correctly returns all visible
books across all libraries, not just test-created books.

This validates that the filter works correctly while being resilient
to dynamic dev database content.

Fixes: #test-isolation-library-filter

cmd/server/tests/search_test.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 	"net/http/httptest"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -387,14 +388,14 @@ func TestCollectionSearchLibraryFilter(t *testing.T) {
 		query         string
 		libraryID     string
 		expectedCount int
-		shouldContain string
+		shouldContain string // Comma-separated list of book IDs to check
 	}{
 		{
-			name:          "no filter - both books",
+			name:          "no filter - both test books present",
 			query:         "Harry",
 			libraryID:     "",
-			expectedCount: 2,
-			shouldContain: "", // Either book
+			expectedCount: 0,                       // Skip exact count check (dev database has dynamic data)
+			shouldContain: book1ID + "," + book2ID, // Both test books should be present
 		},
 		{
 			name:          "filter library 1",
@@ -447,14 +448,21 @@ func TestCollectionSearchLibraryFilter(t *testing.T) {
 			}
 
 			if tt.shouldContain != "" {
-				found := false
+				// shouldContain can be comma-separated list of book IDs
+				requiredIDs := strings.Split(tt.shouldContain, ",")
+				resultIDs := make(map[string]bool)
 				for _, book := range result {
-					if book["id"] == tt.shouldContain {
-						found = true
-						break
+					resultIDs[book["id"].(string)] = true
+				}
+
+				missingIDs := []string{}
+				for _, requiredID := range requiredIDs {
+					if !resultIDs[requiredID] {
+						missingIDs = append(missingIDs, requiredID)
 					}
 				}
-				require.True(t, found, "Expected book %s not found in results", tt.shouldContain)
+
+				require.Empty(t, missingIDs, "Expected books %s not found in results", strings.Join(missingIDs, ", "))
 			}
 		})
 	}