Adding logs for exact repo mismatch and outputs

.github/workflows/test.yml

@@ -17,4 +17,5 @@ jobs:
           node-version: 12
       - run: yarn install
       - run: yarn lint
+      - run: yarn build
       - run: yarn test

__tests__/main.test.ts

@@ -17,11 +17,35 @@ test('wait 500 ms', async () => {
 });
 
 // shows how the runner will run a javascript action with env / stdout protocol
-test('test runs', () => {
+test('test runs', async () => {
   process.env['INPUT_MILLISECONDS'] = '500';
   const ip = path.join(__dirname, '..', 'lib', 'main.js');
   const options: cp.ExecSyncOptions = {
     env: process.env,
   };
-  console.log(cp.execSync(`node ${ip}`, options).toString());
+
+  const result = await new Promise<{stdout: string, stderr: string, err: cp.ExecException|null}>((resolve) => {
+    // cp.execSync will throw an error if the command returns a non-zeo
+    // status, which may or may no happen depending on the environment
+    // this test is run (i.e. locally vs on a GitHub Action).
+    cp.exec(`node ${ip}`, options, (err, stdout, stderr) => {
+      resolve({
+        stdout,
+        stderr,
+        err,
+      });
+    });
+  });
+  // The error returned locally is different from the error we get when running in an action.
+  // However, both will be prefixed with `::error::` by the @actions/core library.
+  expect(result.stdout).toContain('::error::');
+  expect(result.stderr).toContain('');
+
+  // Depending on whether we run locally or on a GitHub action we get
+  // different results.
+  if (result.err) {
+    console.log('An error was returned by lib/main.js:', result.err);
+  } else {
+    console.log(`No error returned by lib/main.js`)
+  }
 });