diff --git a/runtimes/ruby.nix b/runtimes/ruby.nix
index c2399e9..e00fb37 100644
--- a/runtimes/ruby.nix
+++ b/runtimes/ruby.nix
@@ -20,14 +20,14 @@ in piston.mkRuntime {
         # standard output test
         (piston.mkTest {
             files = {
-                "test.rb" = ''
+                "file0.code" = ''
                     puts("OK");
                 '';
             };
             args = [];
             stdin = "";
             packages = [];
-            main = "test.rb";
+            main = "file0.code";
         })
         # args test
         (piston.mkTest {
diff --git a/runtimes/swift.nix b/runtimes/swift.nix
index 65c6a45..9d9d728 100644
--- a/runtimes/swift.nix
+++ b/runtimes/swift.nix
@@ -3,25 +3,24 @@ let
     pkg = pkgs.swift;
 in piston.mkRuntime {
     language = "swift";
-    version = "5.4.2";
+    version = "5.4.2"; # pkg.version attribute is missing, so pinning it to 5.4.2
     aliases = [];
 
     run = ''
-        ls ${pkg}
         ${pkg}/bin/swift -module-cache-path . "$@"
     '';
 
     tests = [
         (piston.mkTest {
             files = {
-                "test.swift" = ''
+                "file0.code" = ''
                     print("OK");
                 '';
             };
             args = [];
             stdin = "";
             packages = [];
-            main = "test.swift";
+            main = "file0.code";
         })
     ];
 }
\ No newline at end of file