Check custom output instead of versions.

Running fake binaries there was no way to get local versions of node or yarn. Am I missing something?

packages/pkg-tests/pkg-tests-specs/sources/script.js

@@ -12,21 +12,21 @@ module.exports = (makeTemporaryEnv: PackageDriver) => {
     test(
       `it should run scripts using the same Node than the one used by Yarn`,
       makeTemporaryEnv({scripts: {myScript: `node --version`}}, async ({path, run, source}) => {
-        await makeFakeBinary(`${path}/bin/node`, { exitCode: 0 });
+        await makeFakeBinary(`${path}/bin/node`, { exitCode: 0, output: `local node` });
 
         await expect(run(`run`, `myScript`)).resolves.toMatchObject({
-          stdout: `${process.version}\n`,
+          stdout: `"local node"\n`,
         });
       }),
     );
 
     test(
       `it should run scripts using the same package manager than the one running the scripts`,
       makeTemporaryEnv({scripts: {myScript: `yarn --version`}}, async ({path, run, source}) => {
-        await makeFakeBinary(`${path}/bin/yarn`, { exitCode: 0 });
+        await makeFakeBinary(`${path}/bin/yarn`, { exitCode: 0, output: `local yarn` });
 
         await expect(run(`run`, `myScript`)).resolves.toMatchObject({
-          stdout: (await run(`--version`)).stdout,
+          stdout: `"local yarn"\n`,
         });
       }),
     );