error: builder for '/nix/store/l55dfs3715ip798nc4ldhqkgkc4zwx35-gst-editing-services-aarch64-unknown-linux-gnu-1.26.0.drv' failed with exit code 1;
       last 25 log lines:
       > Configuring ges-version.h using configuration
       > Program flex found: YES (/nix/store/bd8nq53jkv2qyrgjw3c8alqzf6131vza-flex-2.6.4/bin/flex)
       > Did not find pkg-config by name 'pkg-config'
       > Found pkg-config: NO
       > WARNING: Could not detect glib version, assuming 2.54. You may get build errors if your glib is older.
       > Did not find CMake 'cmake'
       > Found CMake: NO
       > Build-time dependency gio-2.0 found: NO (tried pkgconfig and cmake)
       > Program glib-compile-resources found: YES (/nix/store/adzh287p7iwf5j6l9xkffzcm9vbszjvw-glib-2.84.3-dev/bin/glib-compile-resources)
       > Run-time dependency gobject-introspection-1.0 found: YES 1.84.0
       > Build-time dependency gobject-introspection-1.0 found: NO (tried pkgconfig and cmake)
       > Program g-ir-scanner found: YES (/nix/store/hmasr6h4hy2frylcipbiyzvxq0zbya2f-gobject-introspection-wrapped-1.84.0-dev/bin/g-ir-scanner)
       > Build-time dependency gobject-introspection-1.0 found: NO (tried pkgconfig and cmake)
       > Program g-ir-compiler found: YES (/nix/store/hmasr6h4hy2frylcipbiyzvxq0zbya2f-gobject-introspection-wrapped-1.84.0-dev/bin/g-ir-compiler)
       > Run-time dependency bash-completion found: YES 2.16.0
       > C++ compiler for the host machine: aarch64-unknown-linux-gnu-g++ (gcc 14.3.0 "aarch64-unknown-linux-gnu-g++ (GCC) 14.3.0")
       > C++ linker for the host machine: aarch64-unknown-linux-gnu-g++ ld.bfd 2.44
       > Run-time dependency gstreamer-plugins-base-1.0 found: YES 1.26.0
       > Run-time dependency gstreamer-plugins-bad-1.0 found: YES 1.26.0
       > Program gst-validate-launcher found: NO
       > Program gst-tester-1.0 found: NO
       >
       > tests/validate/meson.build:11:13: ERROR: Program 'gst-tester-1.0' not found or not executable
       >
       > A full log can be found at /build/gst-editing-services-1.26.0/build/meson-logs/meson-log.txt
       For full logs, run 'nix log /nix/store/l55dfs3715ip798nc4ldhqkgkc4zwx35-gst-editing-services-aarch64-unknown-linux-gnu-1.26.0.drv'.
error: 1 dependencies of derivation '/nix/store/kv6xbcch3s16y9z4d32z9jyvwwyj1wby-rygel-aarch64-unknown-linux-gnu-0.44.2.drv' failed to build
error: 1 dependencies of derivation '/nix/store/nbky4pr0v6ksgpbsf2dlzl21qgzfmx31-etc.drv' failed to build
error: 1 dependencies of derivation '/nix/store/pa98ipw6w5bcfr8lnv96fr42pf2z3i8i-system-path.drv' failed to build
error: 1 dependencies of derivation '/nix/store/1gpjwia4375n2szrsinvjyzxzc8wyf61-nixos-system-quadphone-25.11.20250812.005433b.drv' failed to build
error: 1 dependencies of derivation '/nix/store/c6rjynjj7n5l034z06v4061xm0r3bl07-ukify.conf.drv' failed to build
error: 1 dependencies of derivation '/nix/store/2yj58y4aygy7qf4y6ssky5smramdvgrq-image.drv' failed to build

This should fix that

diff --git a/pkgs/development/libraries/gstreamer/ges/default.nix b/pkgs/development/libraries/gstreamer/ges/default.nix
index 2e2a9fdae3fa..5ceada67a73f 100644
--- a/pkgs/development/libraries/gstreamer/ges/default.nix
+++ b/pkgs/development/libraries/gstreamer/ges/default.nix
@@ -10,6 +10,7 @@
   gst-plugins-base,
   gst-plugins-bad,
   gst-devtools,
+  gstreamer,
   libxml2,
   flex,
   gettext,
@@ -43,6 +44,7 @@ stdenv.mkDerivation (finalAttrs: {
     gobject-introspection
     python3
     flex
+    gstreamer # for gst-tester-1.0
   ]
   ++ lib.optionals enableDocumentation [
     hotdoc

I'm still building deps