Test that categories all have the same child type (github#25392)

* Track category child types

* Test that category children are all of the same type

* Add custom error message

Co-authored-by: Grace Park <gracepark@github.com>

Co-authored-by: Grace Park <gracepark@github.com>

tests/content/category-pages.js

@@ -66,7 +66,11 @@ describe('category pages', () => {
     describe.each(categoryTuples)(
       'category index "%s"',
       (indexRelPath, indexAbsPath, indexLink) => {
-        let publishedArticlePaths, availableArticlePaths, indexTitle, categoryVersions
+        let publishedArticlePaths,
+          availableArticlePaths,
+          indexTitle,
+          categoryVersions,
+          categoryChildTypes
         const articleVersions = {}
 
         beforeAll(async () => {
@@ -76,9 +80,24 @@ describe('category pages', () => {
           const indexContents = await readFileAsync(indexAbsPath, 'utf8')
           const { data } = matter(indexContents)
           categoryVersions = getApplicableVersions(data.versions, indexAbsPath)
+          categoryChildTypes = []
           const articleLinks = data.children.filter((child) => {
             const mdPath = getPath(productDir, indexLink, child)
-            return fs.existsSync(mdPath) && fs.statSync(mdPath).isFile()
+
+            const fileExists = fs.existsSync(mdPath)
+
+            // We're checking each item in the category's 'children' frontmatter
+            // to see if the child is an article by tacking on `.md` to it.  If
+            // that file exists it's an article, otherwise it's a map topic.  A
+            // category needs to have all the same type of children so we track
+            // that here so we can test to make sure all the types are the same.
+            if (fileExists) {
+              categoryChildTypes.push('article')
+            } else {
+              categoryChildTypes.push('mapTopic')
+            }
+
+            return fileExists && fs.statSync(mdPath).isFile()
           })
 
           // Save the index title for later testing
@@ -152,6 +171,19 @@ describe('category pages', () => {
           })
         })
 
+        test('categories contain all the same type of children', () => {
+          let errorType = ''
+          expect(
+            categoryChildTypes.every((categoryChildType) => {
+              errorType = categoryChildType
+              return categoryChildType === categoryChildTypes[0]
+            }),
+            `${indexRelPath.replace('index.md', '')} contains a mix of ${errorType}s and ${
+              categoryChildTypes[0]
+            }s, category children must be of the same type`
+          ).toBe(true)
+        })
+
         // TODO: Unskip this test once the related script has been executed
         // Docs Engineering issue: 963
         test.skip('slugified title matches parent directory name', () => {