config(toolkits): check for presence of test files in PRs (aws#5398)

## Problem
Tests aren't being written

## Solution
Add an action that checks for the presence of test files in a PR. If there are no tests then create a comment on the PR

Author: jpinkney-aws

.github/workflows/node.js.yml

@@ -32,6 +32,12 @@ jobs:
             - uses: actions/setup-node@v4
               with:
                   node-version: '20'
+            - name: Check for tests
+              uses: actions/github-script@v7
+              with:
+                  script: |
+                      const notify = require('.github/workflows/notify.js')
+                      await notify({github, context})
             - name: Check PR title
               run: |
                   node "$GITHUB_WORKSPACE/.github/workflows/lintcommit.js"

.github/workflows/notify.js

@@ -0,0 +1,59 @@
+/*!
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+const needsTestFiles =
+    'This pull request modifies files in src/ but no tests were added/updated. Confirm whether tests should be added or ensure the PR description explains why tests are not required.'
+
+/**
+ * Remind partner teams that tests are required. We don't need to remind them if:
+ *  1. They did not change anything in a src directory
+ *  2. They already have test files in the PR
+ *  3. We've already told them in a previous PR comment
+ */
+module.exports = async ({ github, context }) => {
+    const owner = context.repo.owner
+    const repo = context.repo.repo
+
+    const response = await github.rest.repos.compareCommitsWithBasehead({
+        owner,
+        repo,
+        basehead: `${context.payload.pull_request.base.ref}...${context.payload.pull_request.head.ref}`,
+    })
+
+    const filenames = response.data.files.map((file) => file.filename)
+
+    // Check if src directory changed
+    const srcFiles = filenames.filter((file) => file.includes('src/'))
+    if (srcFiles.length === 0) {
+        console.log('Did not find src files in the code changes')
+        return
+    }
+
+    // Check if test files were added or modified
+    const testFiles = filenames.filter((file) => file.endsWith('.test.ts'))
+    if (testFiles.length > 0) {
+        console.log('Found test files in the code changes')
+        return
+    }
+
+    // Check for prior comments on the PR
+    const comments = await github.rest.issues.listComments({
+        owner,
+        repo,
+        issue_number: context.payload.pull_request.number,
+    })
+
+    if (comments.data.some((comment) => comment.body.includes(needsTestFiles))) {
+        console.log('Found prior comment indicating tests are needed')
+        return
+    }
+
+    await github.rest.issues.createComment({
+        issue_number: context.issue.number,
+        owner,
+        repo,
+        body: needsTestFiles,
+    })
+}