Current round of tests pass, but filter function is failing to include when groups match in use.

pkgs/development/ruby-modules/bundler-env/test.nix

@@ -5,44 +5,24 @@ nix-build -E 'with import <nixpkgs> { }; callPackage ./test.nix {}' --show-trace
 Confusingly, the ideal result ends with something like:
 error: build of ‘/nix/store/3245f3dcl2wxjs4rci7n069zjlz8qg85-test-results.tap.drv’ failed
 */
-{ writeText, lib, ruby, defaultGemConfig, callPackage }:
+{ stdenv, writeText, lib, ruby, defaultGemConfig, callPackage }@defs:
 let
   test = import ./testing.nix;
   tap = import ./tap-support.nix;
+  stubs = import ./stubs.nix defs;
+  should = import ./assertions.nix { inherit test lib; };
 
-  bundlerEnv = callPackage ./default.nix {};
-  basicEnv = callPackage ./basic.nix {};
+  basicEnv = callPackage ./basic.nix stubs;
+  bundlerEnv = callPackage ./default.nix stubs // {
+    inherit basicEnv;
+  };
 
   testConfigs = {
     groups = ["default"];
     gemConfig =  defaultGemConfig;
     confFiles = "./testConfs";
   };
-  functions = (import ./functions.nix ({ inherit lib ruby; } // testConfigs));
-
-  should = {
-    equal = expected: actual:
-    if actual == expected then
-    (test.passed "= ${toString expected}") else
-    (test.failed "'${toString actual}'(${builtins.typeOf actual}) != '${toString expected}'(${builtins.typeOf expected})");
-
-    beASet = actual:
-    if builtins.isAttrs actual then
-    (test.passed "is a set") else
-    (test.failed "is not a set, was ${builtins.typeOf actual}: ${toString actual}");
-
-    haveKeys = expected: actual:
-    if builtins.all
-      (ex: builtins.any (ac: ex == ac) (builtins.attrNames actual))
-      expected then
-      (test.passed "has expected keys") else
-      (test.failed "keys differ: expected [${lib.concatStringsSep ";" expected}] have [${lib.concatStringsSep ";" (builtins.attrNames actual)}]");
-
-    havePrefix = expected: actual:
-    if lib.hasPrefix expected actual then
-    (test.passed "has prefix '${expected}'") else
-    (test.failed "prefix '${expected}' not found in '${actual}'");
-  };
+  functions = (import ./functions.nix ({ inherit lib; ruby = stubs.ruby; } // testConfigs));
 
   justName = bundlerEnv {
     name = "test";
@@ -66,9 +46,9 @@ let
     [
       (should.haveKeys [ "name" "env" "postBuild" ])
       {
-        name = should.equal "test-0.1.2";
+        name = should.equal "test";
         env = should.beASet;
-        postBuild = should.havePrefix "nananana";
+        postBuild = should.havePrefix "/nix/store";
       }
     ])
   ];