tests: move fixtures to dedicated dir

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I9d6ce6a264780f215b1b57d947b5264c6a6a6964

tests/fixtures/select_or_default.nix

@@ -0,0 +1,19 @@
+# Test selection with 'or' default
+let
+  attrs = {
+    a = 1;
+    b = 2;
+  };
+in {
+  # Attribute exists - should use value from attrs
+  has_attr = attrs.a or 999;
+
+  # Attribute doesn't exist - should use default
+  missing_attr = attrs.c or 100;
+
+  # Nested default expression
+  nested = attrs.d or (attrs.a + attrs.b);
+
+  # Default with literal
+  with_string = attrs.name or "default_name";
+}